General information
General information
Most single phase applications use the bridge or full wave circuits (center tap
winding).
Transformers play a very important role in any system as the interface between
mains power and the control system. The transformer is used to reduce the supply
voltage to a value suitable for a control system, and also to isolate the control
circuits from the supply for safety reasons.
A bridge rectifier requires a fuse a 1,6 x DC current on the secondary side.
The lower secondary AC voltage from the transformer is converted to DC using a
half wave, full wave or bridge rectifier. These differences are shown below.
Rectifier circuits
Half wave
Full wave
Principle
circuits
Prinzipschaltung
Ieff
IGl
Ieff
Ueff
UGl
Bridge
UGl
RL
RL
Ripple frequency
at f = 50 Hz
50 Hz
I2
I1
Ueff
I2
Ueff2
100 Hz
Three
phase bridge
Ieff
Ieff
IGl
Ueff1
Three
phase star
}Ueff
}Ueff
IGl
I1 UGl
RL
100 Hz
UGl
150 Hz
Ieff
IGl
}Ueff
}Ueff
UGl
RL
RL
300 Hz
Mains voltage
Temperature range
At present, the nominal mains supply voltage varies between countries. By the
year 2003, the European norm voltage will become 230 V single phase and 400 V
three phase.
In use, due to internal losses, some heat will be generated. This heat is dissipated
by the circulating air currents around the unit. If cooling fins are provided, their
surfaces should be vertical.
The unit may be fully loaded in an ambient temperature of up to 60 °C.
Supply voltages to DIN IEC 38
Example shows full power output even at 60 °C
190V
until 2003
after 2003
200 V
210 V
min. 207 V
min. 207 V
220 V
230 V
240 V
250 V
260 V
max. 244 V
max. 253 V
The voltage of 230 V AC is in a transitional phase until the year 2003. Presently,
expected over voltage are around +6 %. After 2003, this tolerance will be
extended to +10 %. Murrelektronik power supplies are already designed to accept
the future European norm voltages of 230 V AC or three phase 400 V AC.
4.1.1
Nom.current
75 %
50 %
25 %
0%
0°
10 ° 20°
30° 40° 50° 60° 70°
80° 90° 100° C
General information
Power supply units with transformers
The galvanic isolation of the input
and output sides as well as the
alteration of the mains voltage (i.e.
into a low voltage) is achieved by
the transformer.
Industrial standards
Components that are used to build
Murrelektronik power supplies meet
international standards as do many of
the power supplies themselves. For
example, the automotive fuses used
in the MNG and MDG can be obtained
anywhere in the world.
The power supply units to EN
60742 are built with either top or
side mounted bridge rectifier and
electronics. This both protects the
electronics and enables the units to
meet touch protection guidelines
(VBG4).
Linear regulated power supplies - NLS
In applications where less than 5 A
is required, it is often not practicle
to replace linear regulated units
with primary switch mode units.
This is particularly true where the
whole system is supplied by an
unregulated or large switch mode
unit. Output voltages can become
corrupted due to long cable lengths,
valves, contactors, other inductive
loads and DC/DC converters. This
can lead to, in the worst case,
destruction of sensitive equipment
or electronics. Areas such as
measurement, process control, and
medical machinery are especially
susceptible to these problems.
Of special note with this range of
power supplies, is the capabilty to
provide excess current when
necessary. This can be anything up
to many times the nominal current
and dependent on the level of over
current necessary, lasting up to a
few minutes.
All transformers/ power supply
units are fitted with angled fixing
brackets and key holes to aid
simple mounting.
Power supply single and three phase smoothed
MEN/MNG/MPL/MDG
The single phase power supply units (MEN, MNG) and three phase power supply units
(MPL, MDG) have been built to meet modern requirements. They have been designed
with reliability and safety a primary concern.
Compact size
Clever designs achieve minimal
space requirements allowing these
units to be used in applications
where space is at a premium. This is
especially important in modern
industry where control panels are
reducing in size and machines
becoming modular.
Primary switched power supply units
In this concept, the input voltage is rectified, smoothed and converted to high
frequency AC. This is transformed to a lower voltage by a small and highly efficient
ferrite cored transformer, and further stabilized.
The advantages are high power to size and weight ratios.
4.1.2
General information
Primary switch mode PIPIncreasingly demanding applications in modern industry require new solutions. The
problem of unreliable power sources is a problem for all especially in export. Those
who require an exactly defined output voltage, often face a rude awakening. In such
situations, only regulated power supplies should be used.
Designed for world-wide use, the MCS and MPS units have all the important and
required international approvals.
The features integrated in the PIP range set a new standard in industry.
All these components together mean that a permanent power source is available
to your system. Problems of mains failure and interference become a thing of the
past.
Note for Murrelektronik Power Supplies that do not fulfil the
requirements of the EN61000-3-2 regarding harmonic.
Due to its small size, the MCS units
can be used in a wide variety of
applications, where space is at a
premium.
Attention:
This unit was designed for application in industrial environment
(closed energy networks) and do not fulfills the requirements
of the EN61000-3-2 regarding harmonic.
The MPS units surpass any other
power supply inregards to
functionality. The extensive
requirements you had with your PLC
and automation systems are now
available in this power supply
family.
The power supply may only be connected to public energy networks
• If the total measured power is greater than 1 kW
• If the total input current per conductor exceeds 16 A
Integrated UPS - function as standard
All 24 V DC units of 10 A and
above, can easily be converted into
uninterruptable power supplies by
adding a few simple products:
• two maintenance free 12 V lead acid batteries provide the power
• an under voltage protection relays prevent deep discharge
• a battery circuit fuse prevents short circuit and monitors the float charging.
4.1.3
• If the measured power is under 75 W (in the future
50 W) and do not have loads for illumination.
Notice:
At parallel operation should be considered the sum
of the individual power measurements
• If the unit is supplied with less then 220 V (neutral
outgoing connection)
This restrictions are valid from January 1, 2001 in all european
countries. Other countries can also make use of these.
General information
Important terminology explained
In rush current limitng
A circuit or component (resistor, NTC) is used to lower the inrush current caused by
switching a load, to an acceptable level.
Over voltage protection
VDR: against short term spikes.
Thyristor (crowbar): generates a short circuit. This is electronically monitored and
the output switched off.
EMC
Elektro Magnetic Compatability (Interference emission and susceptibility).
It is defined as the ability of an electrical product to continue to function problem
free in its environment. Differentiations are made between:
• Industrial:
High levels of interference are allowed (EN 50082)
• Domestic:
Low levels of emission which is then filtered out by other
units (EN 50081)
The optimum product is one which can withstand high levels of interference
(EN 50082-2) while at the same time emitting very little. (EN 50081-1).
Over heating protection
Using a thermal switch, overheating is recognized and the output voltage switched
off. Dependent on the unit, either an alarm is sent or the unit automatically
restarts after a cooling down period.
Certification, Approvals and Manufacturers marks
Approvals make the use of products throughout the world much simpler.
UL:
EN 61558
European norm for power supplies with transformers; follow the EN 60742.
EN 55022
European norm, based on VDE 0878 with respect to electromagnetic compatibilty
in IT and telecommunications installations.
EN 60950
European norm, based on VDE 0805 with respect to safety in IT and
telecommunications installations including office equipment.
Inrush - Current
Input current spike, caused by the switching of electrical equipment, which is
drawn from the mains supply.
Power Factor Correction (PFC)
Power Factor Correction is the correction of the phase between current and
voltage.
Underwriter Laboratories Inc.
An independant organization which tests the safety of products in the USA
and gives them certification. Approved products and the manufacturing
facilities are regularly re-assesed.
UL 1950 recognized
UL 508
cUL:
listed
Test mark of the Underwriter Laboratories Inc. for the Canadian market.
UL 1950 recognized (testing equates to the “CSA”.)
UL 508
listed
CSA: Canadian Standard Association
Independant Canadian product safety testing organization
SEE:
MTBF - number
Mean Time Between Failure is the statistical analysis of the average lifespan of a
product.
Service de l’Energie de l’Etat
Luxemburg test organization. Products are tested to European
norms. Similar to the VDE tests
Mains failure bridging time
The length of time during mains failure in which the power source remains at full
strength.
ENEC: European safety mark for electrical products. It is very similar
to the individual countries tests such as VDE, SEE, the
advantage is that this test mark is presently accepted by
22 European countries.
PELV
Protected Extra Low Voltage is a safety low voltage with integrated earth.
CE:
Redundance
Parallel operating power supply units. In case of failure of one unit another will
take over the complete load.
Placed on a product by the individual manufacturer to show that
the relevant European guidelines have been met. Each product
also has a certificate of conformity, which lists all of the norms and
guidelines which are applicable.
SELV
Separated Extra Low Voltage is a safety safe voltage without attached protective
grounding.
4.1.4