POWER FACTOR
CORRECTION
Components & Systems
August 2002
Table of Contents
What is Power Factor
1
ϕ mean
What does Cosϕ
1
Disadvantages of Low Power Factor
1
Improving Power Factor
1
Power Factor Correction using Capacitors
2
Centralised Compensation
2
Substantiating Power Factor Costs
2
Calculating Capacitor Requirements
2
Power Factor Components
3
- Capacitors
4-7
- Contactors
4-5
- Fuse Protection
5
- Isolating
6
- Reactive Control Relay
7
Series 4000 Rack System
8-10
Rack System Components
8-10
- Capacitors
9
- Contactors
9
- Fuse Protection
9
- Busbars
9
Series 5000 Power Factor Systems
10
Harmonics
11
What are Harmonics?
11
Series 6000 Harmonic Racks
11
Series 7000 Harmonic Systems
12
Power Factor Correction
What is power factor correction?
Disadvantages of Low Power Factor
Power factor is simply a name given to the ratio of “actual” power
(active power) being used in a circuit, expressed in watts or more
commonly kilowatts (kW), to the power which is “apparently” being
drawn from the mains, expressed in volt-ampere or more commonly
kilo volt-ampere (kVA).
1. Increased authorities cost since more current has to be transmitted,
and this cost is directly billed to consumers on maximum demand
kVA systems.
P.F.
2. Causes overloaded generators, transformers and distribution lines
within a plant, resulting in greater voltage drops and power losses, all
representing waste, inefficiency and needless wear and tear on
industrial electrical equipment.
Active Power (kW)
Apparent Power (kVA)
=
All modern industries utilise electrical energy in some form or other.
Two basic categories of load are encountered in alternate current
(AC) networks.
3. Reduces load handling capability of the plants electrical system.
Most electrical supply authorities have changed to kVA demand
systems from the inefficient kW demand system. Consumers are
now billed and penalised for their inefficient systems according to the
apparent power being used. In future, consumers will be penalised
for plants with power factor below a pre-determined value.
1. Resistive Loads
Devices containing only resistance e.g. incandescent lamps, heaters,
soldering irons, ovens, etc.
The current drawn from the supply is directly converted into heat or
light. Since the voltage is assumed to be constant, the actual power
(kW) being used is identical to the apparent power (kVA) being drawn
from the line. The power factor is therefore unity or 1. In these purely
resistive circuits, the current and voltage sinewave peaks occur
simultaneously and are said to be “in phase”.
Improving Power Factor
The most practical and economical power factor improvement device
is the capacitor. As stated previously, all inductive loads produce
inductive reactive power (lagging by a phase angle of 90°).
Capacitors on the other hand produce capacitive reactive power,
which is the exact opposite of inductive reactive power. In this
instance, the current peak occurs before the voltage peak, leading by
a phase angle of 90°. By careful selection of capacitance required, it
is possible totally cancel out the inductive reactive power when
placed in circuit together.
2. Inductive Loads
All motors and transformers depend on magnetism as the basis of
their operation. Magnetism is a force and in the physical sense is not
consumed. In AC motors and transformers, magnetic forces are only
required periodically. Consequently, a permanent magnet cannot be
used and the necessary magnetism is produced by electrical means.
The electrical current needed for this purpose is not fully utilised.
Having produced the magnetic force, the current flows back to the
power station again. This current is called the reactive current in contrast to the active current which performs work and is fully utilised in
so doing. Although the reactive current is not utilised, it imposes a
load on the electrical distribution system and supply authorities
demand payment for this load according to specific tariffs.
kW
ϕ1
KVA2
KV
A1
The current drawn from the supply is made up of two separate kinds
of current “power producing current” and “magnetising current”.
Therefore the current flowing in an AC circuit (unless corrected) is
generally larger than is necessary to supply the power being by the
expended point.
To prevent the continual flow of reactive current back and forth
between the load and power station, a capacitor, which is in effect a
reactive current storage device, is connected in parallel with the load.
The reactive current supplied by the power station and used for the
magnetic force when the load is switched on does not now return to
the power station but instead flows into the capacitor and merely
circulates between the latter and the load. Consequently the distribution lines from the power station are relieved of the reactive current.
Reactive power and active power flow through the motor or transformer. Geometrical calculation of these two powers yield the apparent
power. The ratio of the active and apparent power is denoted by
cosϕ and indicates what fraction of apparent power flowing is actually
used by the motor.
Active Power (kW)
Capacitors can therefore be utilised to reduce kVA and electrical
costs. Improved power factor results in:
ϕ
App
aren
Inductive Reactive
Power (kVAr)
t Po
wer
Capacitor
kVAr
Required
Cosϕ1 is the kVA used before Power Factor Improvement equipment
was added to the network.
Cosϕ2 is the kVA used after Power Factor improvement equipment
was added to the network.
ϕ mean?
What does Cosϕ
Fig. 1
ϕ2
1. Reduced kVA charges
(kVA
)
2. Improved plant efficiency
3. Additional loads can be added to the system
As can be seen from Fig. 1, the apparent power is greater than the
active power and hence the power factor is a value considerably less
than unity.
4. Reduced overloading of cables, transformers,
switchgear, etc.
5. Improved starting torque of motors
P.F.
=
Reactive Power (kW)
Apparent Power (kVA)
=
ϕ
Cosϕ
6. Reduce fuel requirements to generate power due to lower losses.
1
Contents are illustrative only - final details must be checked when placing orders
Power Factor Correction
Centralised Compensation
Power Factor Correction using Capacitors
(Automatic Power Factor Correction)
Two methods of improving power factor using capacitors are:
In large industrial plants where many motors are generally in use or,
when the main reason for power factor is to obtain lower electricity
bills, then centralised compensation is far more practical and economical than individual motor compensation.
a) Individual motor compensation (static capacitors)
b) Centralised compensation (automatic capacitor banks)
In this instance, large banks or racks of capacitors are installed at the
main incoming distribution boards of the plant and are sub-divided
into steps which are automatically switched in or out depending on
specific load requirements by means of an automatic control system,
improving the overall power factor of the network.
Individual Motor Compensation
Most effective correction is obtained by connecting individual capacitors directly to the terminals of each motor. The motor and capacitor can be controlled jointly by the motor switchgear. The capacitor rating should be matched as closely as possible so that the power
factor of the entire plant can be corrected to the optimum value,
irrespective of the number of motors switched on.
Utilising Table 4 for calculating capacitor kVAr size requirements for
power factor correction. The following information must be known
beforehand.
The size of capacitor required may be determined from Table 3 by
taking the motor kW and speed into consideration. Table 3 is a guide
only and no guarantee of correct power factor. The correct method
of maximum capacitor rating can be determined by using the following
formula:
where
Qc
=
0.9Io V√3
Io
Qc
=
=
motor magnetising current
capacitor power in VAr
a) The average plant power factor
b) The maximum running load of the plant in kW
To avoid ferro-resistance and dangerous voltage rises, the total kVAr
required should never exceed 65% of incoming transformer kVA. In
practice, to be absolutely safe, this limit should be set at approx. 50%.
Generally an automatic power factor system consist of:
a)
b)
c)
d)
If the magnetising current is not known, 95% of the motor no-load
current can be used as an approximate value. Care should be taken
not to exceed the value calculated to avoid dangerous overvoltages
and possible self excitation of motors at switch-off.
a main load-break isolator (or circuit breaker)
an automatic reactive control relay
power factor capacitors backed by suitable fuse protection
suitably rated contactors for capacitor switching
The automatic reactive control relay monitors the total network and
will switch-in the required capacitor banks at pre-determined intervals compensating for capacitor discharge times and load dependant
requirements.
Over compensation can cause higher supply voltages which can
cause consequent break down of motor insulation and flashover at
motor terminals. To be safe, rather use standard capacitor sizes (as
indicated below). For this reason, individual motor compensation is
not recommended for motors which are rapidly reversed e.g. cranes,
hoists, etc.
As capacitor switching subjects components to exceptionally high
stresses it is imperative to correctly size and rate all components
utilised in a system.
Table 3
Substantiating Power Factor Correction Costs
Individual Capacitor Rating in kVAr to improve Power Factor to 0.95
or better at all loads.
Motor Rating
kW
2 Pole
3000 rpm
4 Pole
1500 rpm
This question can best be answered by an example. Assuming a
plant has a total load of 500 kW and a power factor (cosϕ) of say 0.75
lagging. Supply authorities kVA demand charge is approximately
R40.00 per kVA (actually above R50.00 in most areas.
Johannesburg is currently R53.10).
6 Pole
1000 rpm
0.75
0.5 kVAr
0.5 kVAr
0.5 kVAr
1.1
0.5 kVAr
0.5 kVAr
1.0 kVAr
1.5
0.5 kVAr
1.0 kVAr
1.0 kVAr
2.2
1.0 kVAr
1.0 kVAr
1.5 kVAr
4.0
1.5 kVAr
1.5 kVAr
2.0 kVAr
5.5
2.0 kVAr
2.0 kVAr
3.0 kVAr
7.5
2.0 kVAr
2.0 kVAr
3.0 kVAr
11.0
3.0 kVAr
4.0 kVAr
5.0 kVAr
15
4.0 kVAr
5.0 kVAr
6.0 kVAr
18.5
5.0 kVAr
7.0 kVAr
8.0 kVAr
22
6.0 kVAr
8.0 kVAr
9.0 kVAr
30
8.0 kVAr
10.0 kVAr
12.0 kVAr
37
10.0 kVAr
12.0 kVAr
14.0 kVAr
45
12.0 kVAr
14.0 kVAr
16.0 kVAr
55
16.0 kVAr
22.0 kVAr
25.0 kVAr
75
18.0 kVAr
25.0 kVAr
30.0 kVAr
90
20.0 kVAr
30.0 kVAr
35.0 kVAr
110
25.0 kVAr
30.0 kVAr
40.0 kVAr
132
35.0 kVAr
40.0 kVAr
40.0 kVAr
160
40.0 kVAr
45.0 kVAr
50.0 kVAr
kW
PF
=
kVA
500 kW
0.75 PF
=
666 kVA
Total costs @ R40.00/kVA = R26,640.00/month
By installing capacitors to improve power factor (cosϕ) to 0.98 lagging
new costs are;
500 kW
0.98 PF
=
510 kVA
Total costs @ R40.00/kVA = R20,400.00/month
therefore savings monthly = R6,240.00
A complete system required to effect power factor from 0.75 to 0.98
(as in above example) would require a system of 360 kVAr which
would currently cost approximately R43,000.00
Power factor correction usually pays for itself well within 12 months
of the initial purchase (7 months in above example ) and continues
saving indefinitely. It therefore stands to reason that more significant
savings can be anticipated with the ever increasing escalation costs
of electricity in the future.
2
Contents are illustrative only - final details must be checked when placing orders
Power Factor Correction
Table 4
Calculating Capacitor Requirements
It is imperative that correct capacitor sizes be selected when calculating capacitor requirements. In the case of centralised compensation, it is recommended that the first capacitor step be equal to half
the value of the following steps, to allow a smooth overall linear correction system.
Existing PF
Cosϕ
Target Power Factor
Required Cosϕ
Before applying
capacitors
0.80
0.85
0.90
0.92
0.95
0.98
1.0
0.40
1.54
1.67
1.81
1.87
1.96
2.09
2.29
Table 4 (right) will assist in calculating capacitor values in specific
applications.
0.42
1.41
1.54
1.68
1.73
1.83
1.96
2.16
0.44
1.29
1.42
1.56
1.61
1.71
1.84
2.04
Prior knowledge of the following is required:
0.46
1.18
1.31
1.45
1.50
1.60
1.73
1.93
0.48
1.08
1.21
1.34
1.40
1.50
1.60
1.83
0.50
0.98
1.11
1.25
1.31
1.40
1.53
1.73
0.52
0.89
1.02
1.16
1.22
1.31
1.44
1.64
0.54
0.81
0.94
1.07
1.13
1.23
1.36
1.56
0.56
0.73
0.86
1.00
1.05
1.15
1.28
1.48
0.58
0.65
0.78
0.92
0.98
1.08
1.20
1.40
a) Power factor before applying capacitors (left vertical column)
b) Required power factor (top horizontal row)
c) Total consumption in kW
The correct capacitor size can be calculated by multiplying the factor
when crossing the horizontal and vertical columns in the table below
by kW.
0.60
0.58
0.71
0.85
0.91
1.00
1.13
1.33
Example:
0.61
0.55
0.68
0.81
0.87
0.97
1.10
1.30
1. Convert the plant load to kW (kVA x PF = kW)
666 kVA x 0.75 Pf = 500 kW (useful power)
0.62
0.52
0.65
0.78
0.84
0.94
1.06
1.27
0.63
0.48
0.61
0.75
0.81
0.90
1.03
1.23
2. To correct a load of 500 kW at 0.75 PF to 0.98 PF.
Follow the 0.75 value (in left vertical column)
horizontally until below the 0.98 value (in top
horizontal row). The factor value is 0.68.
0.64
0.45
0.58
0.72
0.77
0.87
1.00
1.20
0.65
0.42
0.55
0.68
0.74
0.84
0.97
1.17
0.66
0.39
0.52
0.65
0.71
0.81
0.94
1.14
0.67
0.36
0.49
0.63
0.68
0.78
0.90
1.11
0.68
0.33
0.46
0.59
0.65
0.75
0.88
1.08
0.69
0.30
0.43
0.56
0.62
0.72
0.85
1.05
0.70
0.27
0.40
0.54
0.59
0.69
0.82
1.02
0.71
0.24
0.37
0.51
0.57
0.66
0.79
0.99
0.72
0.21
0.34
0.48
0.54
0.64
0.76
0.96
0.73
0.19
0.32
0.45
0.51
0.61
0.73
0.94
0.74
0.16
0.29
0.42
0.48
0.58
0.71
0.91
0.75
0.13
0.26
0.40
0.46
0.55
0.68
0.88
0.76
0.11
0.24
0.37
0.43
0.53
0.65
0.86
0.77
0.08
0.21
0.34
0.40
0.50
0.63
0.83
0.78
0.05
0.18
0.32
0.38
0.47
0.60
0.80
0.79
0.03
0.16
0.29
0.35
0.45
0.57
0.78
0.80
0.13
0.27
0.32
0.42
0.55
0.75
0.81
0.10
0.24
0.30
0.40
0.52
0.72
0.82
0.08
0.21
0.27
0.37
0.49
0.70
0.83
0.05
0.19
0.25
0.34
0.47
0.67
0.84
0.03
3. Capacitor required to correct from 0.75 to 0.98
(power x capacitor from the table value)
500 kW x 0.68 = 340 kVAr
savings:
500 kW @ 0.75 PF
500 kW @ 0.98 Pf
Reduction of
=
=
666 kVA
510 kVA
156 kVA
(23.4% less of transformer load)
0.16
0.22
0.32
0.44
0.65
0.14
0.19
0.29
0.42
0.62
0.86
0.11
0.17
0.26
0.39
0.59
0.87
0.08
0.14
0.24
0.36
0.57
0.88
0.06
0.11
0.21
0.34
0.54
0.89
0.03
0.09
0.18
0.31
0.51
0.90
0.06
0.16
0.28
0.48
0.91
0.03
0.85
0.13
0.25
0.46
0.92
0.10
0.22
0.43
0.93
0.07
0.19
0.40
0.94
0.03
0.16
0.36
0.13
0.33
0.95
3
Contents are illustrative only - final details must be checked when placing orders
Power Factor Components
Power Factor
Specifications
Components,
Systems
3 Phase Monobloc Capacitors 440V
“H” Type 440V, 50 Hz, 3 Phase
(Maximum Voltage 520V - 50Hz)
and
Electromechanica have been involved in all aspects of power factor
correction in our specific environment for some 20 years now, and it
is with this experience gained, that we can confidently recommend,
specific components required in power factor correction, and
complete ready to connect automatic power factor systems.
Alpivar heavy duty capacitors are totally dry units with no impregnation or insulation liquid.
Electromechanica offers a complete range of components and equipment for power factor correction viz.
a)
b)
c)
d)
e)
Power factor capacitors 400-550 volt
Contactors specifically for capacitor switching
Fuse protection components for capacitor banks
Automatic reactive control relays
Special rack systems incorporating capacitors, contactors, fuse
protection and busbars
f) Complete power factor systems 30-1500 kVAr
Alpivar monoblock capacitors utilise windings insulated by a selfextinguishing casing, immersed in thermosetting polyurethane resin
applied under vacuum with excellent heat dissipation qualities
(measured internal temperature is <3°C of ambient).
Capacitors
The unique vacuum potting technique ensures that Alpivar capacitors
have excellent resistance over time and much longer service life than
conventional capacitors.
Traditionally power factor capacitors are made up of single phase
metalized polypropylene windings, placed into a plastic cylinder
impregnated with epoxy resin. These cylinders (windings) are coupled
in a delta configuration (to offer a 3 phase system) and placed into
an enclosed sheet metal box which offers desired protection in the
event of explosion due to undue stresses placed on the capacitor
through potential exposure to overvoltage, increased frequency,
harmonic effects and over temperature.
Capacitor windings incorporate the following internal protection:
• Self healing dielectric (metalized s film)
• Electrical fuse (per winding)
• Effective overpressure disconnecting device (per winding)
This conventional system of capacitor manufacture in no way takes
heating into consideration, (undoubtedly the single most important
factor effecting the overall life of the capacitor). Capacitors have
power losses of ±0.05% (0.5 watts per kVAr) which stands to reason
that a 60 kVAr capacitor for instance, would have to dissipate ±30
watts of generated heat inside a enclosed sheet metal enclosure.
Temperatures measured inside these enclosures could reach 1520°C higher than the ambient temperature that they are exposed to,
drastically effecting the overall life of the capacitor.
The use of 440V capacitors is highly recommended, which generally
accommodate overvoltages in systems due to the presence of harmonics (becoming more prevalent in electrical networks today).
This, in effect, permits a permanent 20% overvoltage factor without
any negative effects on the capacitor itself. (IEC requirements
already anticipate a tolerance of +10%).
In the event of element failure, only the effected element is disconnected from the power circuit, ensuring maximum safety conditions
and leaving unaffected capacitors still in service.
Main Factors Effecting Capacitor Life
Care should be taken when calculating capacitor kVAr requirements in 400V systems as the kVAr rating will be slightly lower when
440V capacitors are utilised.
Faults
Small Faults 15%
Selection criteria for suitable capacitors:
a) Rated at 440V (in low voltage applications)
b) All capacitors utilised within a system should comply fully with
requirements of IEC60831-1/2 and CEI-EN60831-1/2
c) Have a tolerance of -5 ÷ +10%
d) Be rated for operational temperature of at least 50°C
e) Offer permanent overvoltage tolerances of at least 1.15 Un
f) Offer permanent overcurrent tolerances of at least 1.7 In
g) Capacitors should incorporate effective overpressure disconnector
h) Capacitors should be provided with discharge resistors effectively
reducing terminal voltages to less than 50V within 1 minute.
i) Incorporate internal independent fusing
Cause
Solution
Break down of dielectric
within capacitor windings
caused by overvoltages.
Dielectric is perforated
when overvoltage occurs.
Manufactured with selfhealing metalized polypropylene film which
vapourises the metal
around the short circuit to
restore electrical isolation.
Medium Faults 70% Over current / voltages
caused by harmonic
presence and over
temperature which cannot
be overcome by the selfhealing dielectric.
Gas build up within the
capacitor when emitted
caused the deformation
of a membrane which
effectively disconnects
the defective coil from
the circuit.
High Faults 15%
An independent internal
electrical fuse disconnects
the effected coil.
Short circuits.
The inclusion of internal fusing does not substitute the necessity of
external safety devices such as fuse cut-outs or circuit breakers.
Alpivar capacitors associated with patented vacuum potting technique
form a highly advanced unit and incorporate all of the above protections.
Electromechanica offers a range of Alpivar capacitors far exceeding
all of the above requirements.
The capacitors comply fully with international requirements of
IEC60831-1/2, CEI-EN60831-1/2, NF C54 108/9, CSA 22-2 No.190,
UL810.
4
Contents are illustrative only - final details must be checked when placing orders
Power Factor Components
Contactors
Capacitors are rated at 440V to accommodate overvoltages in systems due to the presence of harmonics (becoming more prevalent in
electrical networks today). This accommodates a further 10% overvoltage factor above the 10% tolerance anticipated by IEC requirements. Alpivar capacitors withstand overvoltages of 1.18 Un continuously (24h/24) effectively offering a 30% overvoltage factor when
applied in a 400V system and can operate effectively up to 520V, 50
Hz.
Selection criteria for suitable contactors:
a) Contactors utilised within a system should comply fully with
requirements of IEC/EN60947-4-1
b) Should be rated for operational temperatures of 50°C (ratings
higher than 50°C to 70°C should be reduced by a percentage
equal to the difference between the ambient temperature and
50°C)
c) It is recommended to underrate the contactors by 10%
d) Contactors should be limited to ≤ 120 cycles per hour with an
electrical life of 200,000 cycles
e) Effective limiting inductances should be incorporated
f) Consideration must be made for capacitor discharge times and
reactive control relays should incorporate sufficient delay to
ensure that capacitors are sufficiently discharged before they
are reconnected.
Standard maximum permissible current requirements for conventional
capacitors is 1.3 In.
Alpivar capacitors are designed to withstand up to 2.0 In.
Specifications
Rated Voltage
Internal Protection
:
:
Tolerance
Max. Voltage Overload
Max. Current Overload
Loss Factor
:
:
:
:
Operating Temperature
Insulation Class
:
:
Discharge Resistors
Standards
:
:
Type
VCB1544
VCB2044
VCB2544
VCB3044
VCB4044
VCB5044
VCB6044
VCB7544
VCB8044
VCB9044
VCB10044
(1)
kVAr
440V
15
20
25
30
40
50
60
75
80
90
100
(2)
kVAr
400V
12
17
21
25
33
41
50
62
66
74
83
440V, 50 Hz three-phase
- Self Healing Dielectric
- Electric Fuse (per
element)
- Overpressure disconnecting
device (per element)
±5% capacitance
1.18 Un continuous (24h/24)
2.0 In
<0.3W per kVAr (including
discharge resistors)
-40 - +55°C
6 kV for 1 minute at 50 Hz
(25kV 1.2/50mµS shockwave)
Incorporated (<50 within 1 min)
IEC60831-1 and 2
EN60381-1 and 2
NFC54108-9
CSA22-2No.190
UL810
(3)
Current (A)
per phase
20
26
33
39
52
66
79
98
105
118
131
The contactor during the closing transition is influenced by electrical
currents having high frequencies and high amplitudes. The frequencies
of these currents range between 1 and 10 kHz; the amplitudes must
have values lower than the maximum permissible current peak of the
contactor to be used.
If this condition cannot be verified, it is necessary to use limiting
inductances or special capacitor switching contactors.
Lovato contactors utilised in our systems
are specially designed for capacitor
switching and are equipped with earlymake contacts which introduce resistors to
limit the connecting current of capacitors
for a very brief interval, (2-3 ms) during the
contactor closing. These resistors are
then disconnected from the circuit once
the contactor closing operation is completed
and the current capacity is then conveyed
through the main contacts of the contactor,
dramatically reducing wear of contactors,
capacitors and fuses, ensuring longer life
and reliability of the system.
Dimension
H x W x D
275 x 90 x 225
275 x 90 x 255
275 x 90 x 225
275 x 180 x 225
275 x 180 x 225
275 x 180 x 225
275 x 270 x 225
275 x 270 x 225
275 x 360 x 225
275 x 360 x 225
275 x 360 x 225
L1 L2 L3
1 3 5
A1
A2
2 4 6
T1 T2 T3
(1) Actual Capacitor Rating
(2) Equivalent kVAr Rating
(3) Supply Voltage is 440V
Lovato BF..K Contactors
type
Max. operating Power at
230V
400V
440V
kVAr
kVAr
kVAr
Rated
Current
(A)
Fuse
gG
(A)
40
BF25K00
11
20
22
30
BF40K00
17
30
33
43
63
BF65K00
26
45
50
70
100
BF80K00
34
60
65
90
125
5
Contents are illustrative only - final details must be checked when placing orders
Power Factor Components
Fuse Protection
Mains Isolators
The use of a main incoming isolator is highly recommended, preferably door interlocked to prevent opening of the enclosure with power
applied to the components. As circuit breakers have been known to
cause unnecessary nuisance tripping in many instances the use of
fuses or a fuse switch should be considered if protection of the mains
supply cable is required additionally.
Selection criteria for suitable fuses:
a) Should conform fully to requirements of IEC60269-1,
IEC60269-2-1
b) Should be gl-gG type high rupturing capacity
c) Offer protection for overcurrents and short circuits with
fault levels of up to 50kA
d) Fuse bases should be highly resistant to temperature
withstand up to 120°C and be self-extinguishing - UL94Vo
with a creepage resistance of CTI = 600V.
DF DIN type (knife) fuses have been found to be particularly
suitable for protection of capacitor banks in systems.
Specific fuse protection is essential for each capacitor bank
of a system. Exposure to overvoltage, increased frequency
and the effects of harmonics, permit capacitors to be
continuously overloaded at up to 1.35 times their nominal
rating. This overload as well as high initial switching currents
of the capacitors must be considered when calculating fuse
requirements for capacitor bank protection.
Table 5 (below) will assist in correctly specifying standard fuses as
well as recommended cable sizes for capacitor banks.
Selection criteria for suitable mains isolator:
a) Must be fully compliant with requirements of IEC60947-1/3 as
well as IEC60664, 60269 and 60204
b) Control circuit should be wired through a mounted “early makelate break” auxiliary, effectively allowing the making and breaking action of the isolator to switch “off-load” thus preventing
potential operation of the isolator on fully charged capacitors.
c) Should be door interlocked with enclosure, preventing opening
of enclosure door with live components exposed.
d) Must be sized correctly to accommodate total system current
carrying capacity.
Fuse Bases
Table 5
Rating
kVAr
2
2.5
3
4
5
7.5
10
15
20
25
30
35
40
50
60
70
80
Rated Voltage 440VAC
Rated
Current
A
2.9
3.6
4.3
5.8
7.2
8.6
14.4
21.5
28.5
33.0
39.2
46.5
53.5
66.0
80.0
93.0
108.0
Fuse
Rating
A
10
10
10
10
16
20
25
40
40
63
63
80
80
100
125
160
160
Selection criteria for fuse bases:
Cable
Cross Section
mm2
1.5
1.5
1.5
1.5
2.5
2.5
4
10
10
16
25
35
35
50
70
70
95
a) Should be fully compliant with the requirements of IEC/EN
60269-1/2, VDE0636, DIN43620.
b) Should be made of self-extinguishing material UL94 VO.
c) Be rated for voltages up to 690V.
The df range of polyester fuse bases offer a very high insulation and
are able to withstand extremely high temperatures.
The insulation (IP) protection can be enhanced by additional fuse
and terminal covers.
6
Contents are illustrative only - final details must be checked when placing orders
Power Factor Components
The capability of performing complex calculations regarding reactive
power, permits the rapid switching of capacitor banks in a timeous,
explicit manner, resulting in a drastic reduction in the number of
operations and their homogeneous use.
Reactive Control Relay
Selection criteria for suitable control relays:
a) Must be compliant with requirements of IEC/EN60255-5/6,
IEC60068-2-61/6
b) Should incorporate an accurate power factor indicator
c) Offer clear indication of steps switched-in
d) Must facilitate a suitable delay between disconnection and reconnection of the same step (min 60 sec) even when operated in
manual mode
e) Have a contact rating of at least Ith: 5A-250V (AC1)
f) Ensure balanced/equally distributed use of switching steps
g) Be configurable for stepping 1-1-1.../1-2-2.../1-2-4
h) Allow accurate readings and indication even in the presence of
high harmonic content or waveform distortions.
Besides instantaneous power factor indication, the large LED digital
display also indicates:
• Voltage (True RMS)
• Current (True RMS)
• ∆ kVAr (Indicating the required reactive power to correct to pre-set
value)
A configurable alarm function indicates the following:
Over/Under Voltage
(A.HU/A.LU)
Over/Under Current
(A.HI/A.LI)
Over/Under Compensation (A.HC/A.LC)
The Lovato DCRE range of reactive control relays more than meet
the above requirements. They perform the control and adjustment
functions in a totally digital manner and incorporating latest microprocessor technology, facilitating accurate, reliable power factor
control. An appropriate algorithm ensures accurate operation even
in systems characterised by high harmonic content.
The trend in the market place is to supply systems with separate
auto-off-man selector switches and pilot lights. This trend should be
strongly discouraged as this method of switching overrides the inherent
safety delays incorporated in the controller (which is able to perform
the same function) and exposes contactors to undue stress and a
potentially dangerous situation when operated inadvertently on fully
charged capacitors.
DCRE12
L1 L2 L3
VOLTAGE
1
2
3
4
5 6
7
8
9 10 11 12
C 1
2
3
4
5 6
7
8
9 10 11 12 13
/5A
OV
380-415V
CURRENT
S1 S2
14
15
QS1
Technical Characteristics
DCRE5
DCRE7/12
FU2
FU1
FU13
Supply Circuit
FU12
R
FU14
KM1
R
KM2
KM12
R
Supply Voltage Ue
Operating Limits
Rated Frequency
Maximum Power Consumption
380-415 VAC
-15% ... +10% Ue
50 (or) 60Hz (self configuring)
5.4 VA
2.6 VA
LOAD
R
R
R
TC1
K1
K2
K12
Current Limit
Rated Current Ie
Operating Limits
Overload Capacity
Overload Peak
Note
5A
0.125 ... 5.5A
1.1 Ie
10 x Ie 1s
1) Always ensure that C.T. is connected to the phase not utilised for
supply voltage to controller.
2) Ensure that C.T. is correctly rated for system requirements and
connected in the correct direction.
Reading and Control Range
Voltage Reading Limits
Current Reading Limits
Type of Voltage/Current Reading
Power Factor Adjustment
Re-connection Time of Same Step
Switching Sensitivity
-15% ... +10% Ue
2.5 ... 110% Ie
True RMS
0.85 Inductive - 0.95 Capacitive
5-240 sec
5-600 sec
Relay Output
No. of Outputs
(1 x Isolated can be Alarm Relay)
Contact Arrangement
Rated Capacity Ith
Rated Operating Voltage
Maximum Switching Voltage
5
7 or 12
1 x NO
5A-250V (AC1)
250 VAC
440 VAC
Housing
Version
Dimensions
Protection (IP54 with t/parent cover)
Type of Termination
Flush Mounting
96x96x62mm
144x144x32mm
IP41
Plug-in / screw
7
Contents are illustrative only - final details must be checked when placing orders
Series 4000 Rack
The Series 4000 rack system is a convenient all-in-one component kit for mounting into a standard enclosure to complete a system. The
system incorporates latest developments in capacitor, contactor and fuse technology.
Contactors
Are special capacitor switching type
equipped with early make contacts which
introduce limiting resistances during the
contactor closing operation, whereafter
they are completely disconnected from the
circuit. Drastically reducing stress and
wear of the contactors, capacitors and
fusegear, ensuring longer life and overall
reliability.
Busbars
Are incorporated on
the racks by insulated supports, offering
very high fault levels
suitable for currents
of up to 630A. The
system is expanded
by merely coupling to
busbars of another
rack
Capacitors
Fuseholder
Are potted in thermoset polyurethane
resin under vacuum offering excellent
heat dissipation qualities. They are
mounted onto the rack exposed,
permitting effective airflow from all
sides. The capacitors incorporate the
following internal protections:
• Self Healing Dielectric
• Electrical Fuse
• Overpressure Disconnecting Device
Capacitors are rated at 55°C and can
operate at voltages of up to 520V and
are designed to withstand up to 2.0 In.
Discharge Resistors
Fuses utilised in the rack system provide effective protection from short circuits and
overload conditions. They
are specially designed for
direct mounting onto busbars,
which are incorporated in the
rack.
Enable the capacitors to be
discharged in compliance with
applicable standards. They are
mounted externally to enable
ease of visual inspection.
8
Contents are illustrative only - final details must be checked when placing orders
Power Factor Components
As contactors are wired in the delta loop, current requirements are
lower, thereby decreasing the contacting ratings by √3.
Series 4000 Rack System
The Series 4000 rack system has recently been developed as a
convenient all-in-one component for inclusion into a standard
enclosure or as a complete system. The design combines many
years experience gained in power factor and its application in very
harsh local conditions. Incorporating latest up-to-date technology in
capacitor, contactor and reactive control relay developments.
The table below indicate contactor requirements with 6 terminal
capacitors and conventional 3 phase capacitors.
kVAr 415V
12.5
25
30
40
50
60
75
100
Standard
3ph Capacitor
BF12K10
BF40K10
BF40K
BF65K
BF65K
BF80K
6 Terminal
Capacitor
BF9K10
BF20K10
BF25K10
BF40K
BF40K
BF65K
BF65K
BF80K
Fuses and Fuse Bases
Fuses utilised in the 4000 series rack system are DIN (blade type)
Class gl-gL-gG HRC fuses. They provide effective protection from
short circuits and overload conditions for all 3 phases of the capacitor bank and conform fully to requirements of IEC60269, CEE16,
VDE0636 and DIN57363.
Racks are supplied with capacitor sizes from 25 to 100 kVAr in various
configurations. They incorporate capacitors, special capacitor
switching contactors and fuse protection.
Fuse bases are directly mounted onto a suitably rated, incorporated
busbar system suitable for capacities up to 500 kVAr, offering simple
expansion capabilities by merely coupling to busbars of another rack.
Fuse-link
Type
300063
300100
300160
300160
Capacitors
Capacitors utilised in the Series 4000 rack system are the Alpivar
heavy duty types. They are self-healing and incorporate independent
internal fusing, overpressure protection facilities and are able to withstand permanent overvoltages up to 520V and over current at 2.0 x
In (see pages 4 and 5 for detailed technical specifications).
Capacitors are designed to withstand undue stresses caused by
potential exposure to overvoltage, increased frequency and limited
harmonic effects.
In (A)
63A
100A
160A
160A
Capacitor
Size (kVAr)
25 kVAr
50 kVAr
75 kVAr
100 kVAr
Breaking
Capacity
80 kA
80 kA
80 kA
80 kA
Capacitors are mounted, exposed, offering all-round ventilation with
excellent heat dissipation, ensuring longer life.
The specially designed 6 terminal capacitors utilised in the rack system allow contactors to be wired in the delta loop, reducing current
carrying by 30% on contactors.
L1
5
6
T1
L1
3
4
T2
L2
1
2
T3
L3
Fuse bases are specially designed to directly mount onto busbars
which are incorporated in the rack system. They provide independent
fuse protection of all three phases of each capacitor bank (up to two
banks per rack).
R
L2
S
L3
T
Busbars
Busbars are incorporated on the racks and supported by high
class insulated 3 phase supports, incorporating termination
at the top or bottom of the rack. Standard supplied busbars
are suitable for currents in excess of 630A. Systems are
expanded by merely coupling busbars to those of another
rack.
Contactors
Contactors utilised on the 4000 Series rack system are specifically
designed for capacitor switching. They are equipped with earlymake auxiliary contacts which temporarily introduce limiting
resistances (effectively absorbing peak in-rush currents) during the
contactor closing operation. These resistors are disconnected from
the circuit once the contactor closing operation has been completed
and the capacitor current capacity is then conveyed through the main
contacts of the contactor. This method of operation drastically
reduces wear of contactors, capacitors and fuses, ensuring longer
life and overall reliability of the entire system.
9
Contents are illustrative only - final details must be checked when placing orders
Power Factor Components
Series 4000 Rack System
Series 5000 Complete Power Factor Systems
kVAr
The Series 5000 Power Factor Correct System encompasses
all the advantages of the 4000 Series rack system in a purpose built, floor standing enclosure. The racks are securely
mounted into the enclosure (measuring 550mm wide x
400mm deep) and coupled together via the incorporated busbars of the racks. A mains isolator is included (for top or
bottom entry) and the reactive control relay, door mounted
and connected to the circuit.
Configurable
(kVAr)
Type
440V
400V
40025
25
21
1 x 25
40050
50
41
1 x 50
42050
50
41
1 x 25 + 1 x 25
40075
75
62
1 x 75
42075
75
62
1 x 25 + 1 x 50
40100
100
83
1 x 100
42100
100
83
1 x 50 + 1 x 50
The panel is supplied as a complete floor standing “ready to
connect” system providing effective ventilation and dissipation of heat build-up within the panel. An additional fan
cooling facility can be included for applications where the
environment provides very low airflow.
Dimensions
160
240
525
500
248
400
150 200
550
Advantages of the 4000 Series Rack
a) The rack offers good, effective ventilation for capacitors
b) Capacitor windings (cells) are incased in thermosetting
resin, housing forming (better heat dissipation) longer life
c) Windings independently
1) Internally fused
2) Equipped with an effective internal overpressure device
effectively disconnecting only a damaged cell from the
system leaving remaining good cells still operational
(minimum reduction in overall capacitance)
d) Alpivar heavy duty capacitors are rated at 55°C.
1.18 Un (30% overrating in 400V systems)
2.0 In
e) Special capacitor switching contactors incorporating initial
limiting resistances increase contactor and capacitor life
f) Busbar system incorporated onto rack convenient
expansion capabilities by simply coupling to busbars of
another rack
g) Easy access to all components for maintenance and repair
purposes
Series 5000 Floor Standing Complete Systems
Type
kVAr
440V
kVAr
400V
50150
50175
50200
50250
50275
50300
50350
50375
50400
50450
50475
50500
150
175
200
250
275
300
350
375
400
450
475
500
124
145
165
207
227
248
289
310
331
372
393
413
Steps
(kVAr)
25-25-50-50
25-50-100
25-25-50-100
25-25-50-50-100
25-50-100-100
50-50-100-100
50-3 x 100
25-50-3 x 100
50-50-3 x 100
50-4 x 100
25-50-4 x 100
50-50-4 x 100
Dimension
H x W x D
1500
1500
1500
1500
1500
1500
2100
2100
2100
2100
2100
2100
x
x
x
x
x
x
x
x
x
x
x
x
600
600
600
600
600
600
600
600
600
600
600
600
x
x
x
x
x
x
x
x
x
x
x
x
500
500
500
500
500
500
500
500
500
500
500
500
* Larger sizes available on request
Sizes above 540 kVAr are readily available but in this case
two standard systems with their independent isolators are
utilised, with only one reactive control relay to maintain the
current ratings of incorporated busbars on the racks.
10
Contents are illustrative only - final details must be checked when placing orders
Power Factor Systems
(curve x c). For the 5th harmonic there is an absorption effect
which is more intense at a resonance frequency of 204 Hz
than at 189 Hz.
HARMONICS
What are harmonics?
For the 7th harmonic (=350 Hz) and even more for higher frequencies there is a block effect caused by the filter circuit as
can be seen on the diagram.
Harmonics are undesired signals which are present in electrical
networks that have a frequency multiple of the fundamental:
as they overlap they create a new distorted wave shape
which is no longer sinusoidal.
Electromechanica offer combined solutions for harmonics in
our Series 6000 racks which incorporate capacitors with high
overvoltage and overcurrent capabilities allowing application
into networks, with a degree of interference up to 25%, without the need for reactance. Should the interference be higher, racks incorporating inductances are also offered.
Most modern factories are making increasing use of modern
power electronics. A feature of semi-conductor controlled
devices and drives is to generate a high content of harmonics
in the mains. The result is that resonance occur which leads
to dangerous excess currents which overload capacitors,
cables, fuses and especially contactors.
Degree of
Interference
Harmonics do not originate from power generators but are
produced by non-linear loads which can be divided into three
main groups:
SH
ST
• Loads with variable impedance i.e. arc furnaces, fluorescent
lighting, etc.
• Loads with saturated magnetic circuits i.e. reactors, saturation transformers, induction furnaces, etc.
• Loads that make use of semi-conductor devices i.e. static
rectifiers, static frequency converters, static uninterruptible
power supplies, static induction regulators.
≤ 25%
> 25%
H
SAH
SH (kVA) The weighted total of the harmonic generators present
at the transformer secondary.
Non-linear loads are therefore typical harmonic generators.
ST (kVA) The power rating of the HV / LV transformer
Harmonic currents are load independent and are caused by
the harmonic generator which is dependent on the phase
angle of the power supply. The frequencies occurring form
multiples of the mains rated frequency, since impedance of
the line system rises during increased frequency (whereas te
impedance of capacitors falls). The harmonic current flow
through capacitors installed in the vicinity of the harmonic
generator.
Series 6000 Rack incorporate:
•
•
•
•
•
As a remedy each capacitor can be in series with a reactance.
The inductance is so designed that series resonance frequency below the 5th harmonic results. Usual values are 189
Hz or 205 Hz.
capacitors 25-50-100 kVAr
capacitor switching contactors
anti-harmonic reactor with thermal protection
fuses and fuse holders
suitably rated busbars
The capacitor / reactance combination is inductive at any
frequency above the series resonance. Consequently, a
resonance between mains reactance and capacitor can no
longer occur at a higher mains harmonic.
Reactance XC in Relation to Frequency f
Fig. 3
XC (%) 100
Z (%)
90
z
9H
80
70
60
Z
18
Z
z
4H
20
The Series 6000 racks slide into position and are designed
with metallic shielding of the reactor from the capacitors.
50
40
kVAr
30
20
10
X C(%)
Type
440V
400V
Dimensions
H x W x D
60025
25
21
325 x 700 x 460
60050
50
41
325 x 700 x 460
60100
100
83
325 x 700 x 460
50 100 150 200 250 300 350 400 450 500 550 600 650 700
f (Hz)
The racks can be simply mounted into standard enclosures of
800mm width to be included into systems to be manufactured
or added to existing systems and can be expanded by merely coupling to busbars of another rack.
Fig. 3 above indicates the reactance x c in relation to frequency f. From this it can be seen that in the range of the 5th
harmonic (=250 Hz) the reactance of the capacitor and filter
circuit is lower than that of a capacitor without filter circuit
11
Contents are illustrative only - final details must be checked when placing orders
Power Factor Systems
The Series 7000 Floor Standing Complete
Systems (incorporating anti-harmonic reactors)
Is a complete ready-to-connect enclosed system control
relay, mains isolator all mounted into a suitably ventilated
enclosure ready for installation.
Series 7000 Complete System
Type
440V
kVAr
400V
Dimensions
H x W x D
7125
125
103
2100 x 800 x 600
7150
150
124
2100 x 800 x 600
7175
175
145
2100 x 800 x 600
7200
200
165
2100 x 800 x 600
7250
250
207
2100 x 800 x 600
7275
275
227
2100 x 800 x 600
7300
300
248
2100 x 800 x 600
7350
350
289
2100 x 800 x 600
7400
400
331
2100 x 800 x 600
Larger sizes available on request
12
Contents are illustrative only - final details must be checked when placing orders
Power Factor Equipment
• Low Voltage Equipment
• Capacitor Switching Contacts
• Fusegear
• Reactive Control Relays
• Load-break Switches
• Capacitor Rack Systems
• Anti-harmonic Reactors
• Capacitor Rack Systems incorporating Harmonic Reactors
• Complete Power Factor Systems
• Complete Power Factor Systems incorporating Harmonic Reactors
(www.em.co.za)
(Gauteng)
(Cape Province)
(Kwazulu Natal)
9/11 Data Crescent,
Ormonde Ext 8
P O Box 38980, Booysens 2016
2 Woodbridge Business Park
Koeberg Road, Montague Gardens
P O Box 200, Milnerton 7435
17 Mc Donald Rd,
Congella
P O Box 17317, Congella 4013
Telephone: (011) 249-5000 / 496-2773
Telefax:
(011) 496-2779
E-mail:
info@em.co.za
Telephone: (021) 529-7000
Telefax:
(021) 552-0331
E-mail:
info@em.co.za
Telephone: (031) 205-1571
Telefax:
(031) 205-1625
E-mail:
info@em.co.za