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HAZARDOUS AREA MOTOR/DRIVE PROTECTION PRINCIPLES AND
OPTIMUM SELECTION CRITERIA
Copyright Material PCIC Europe
Paper No. PCIC Middle East ME17-4
Dip.-Ing Hugo Stadler
Eur Ing Steve Jackson MA BSc CEng
Siemens Germany
Siemens UK
Abstract - This paper will provide an overview of
hazardous area classifications including the
implications of the latest IEC standards and the
LV/HV motor & drive protection principles of ‘nonsparking’, ‘increased safety’, ‘flame proof’ and
‘pressurised’. The relative advantages for each
technique will then be discussed for different
scenarios such as atmosphere, overload, starting,
inverter operation, size, weight, flexibility and cost.
Three components are required to make a hazardous
situation: - flammable material, oxygen and an ignition
source.
B. Definition of Zones
Zone 0 - 1 - 2:
Gas & Vapors
Zone 20 - 21 - 22: Dust
N America
Div 1 Class I ~ Gas Zone 1
Div 2 Class I ~ Gas Zone 2
Index Terms – Hazardous Area, Protection, Motors,
Increased Safety, Flame Proof, Non-Sparking, Purge.
Occurrence: rare, short time
( <10h/a)
I.
INTRODUCTION
This paper will cover hazardous area basics, a
description and comparison of motor Ex protection
types followed by advice on matching drives to Ex
motors and a cost evaluation.
II.
HAZARDOUS
DRIVES
AREA
MOTORS
Occurrence: occasional
(10h/a < 1000h/a)
Occurrence: permanent, long term
(>1000h/a)
Fig 2 Hazardous Area Zones
Zones are defined on the probability of a hazard
occurring in that area. Zone 0 which has a permanent
threat of an occurrence is generally not suitable for
any sort of electrical machine.
&
Ignition source
A. Ex-protection in Electrical Apparatus
C.
Precautions
Risk minimization – basic principles according to EN
1127-1.Protection measures have to be undertaken in
the following sequence:
Primary Ex-protection
Prevent hazardous atmospheres
Limit concentration of flammable material
Inertization (add Nitrogen, Carbon Dioxide)
EXPLOSION
Secondary Ex-protection
Avoid every potential ignition source
Tertiary Ex-protection
Limit the consequences of an explosion to a harmless
degree.
Explosive atmosphere:
gas, vapor, fog, dust and air in
Correct dispersion and
concentration
Protection methods for electrical machines are part of
the secondary precaution to avoid every potential
ignition source.
Fig 1 Conditions for Explosion
1
D. Classification of Electrical Equipment
Directive 94/9/EC
Equipment Equipment
group
category
EN 60079-0
EPL
Types of protection Equipment
Equipment
Examples
group
Protection Level
Ex ia
M2
Ex d, Ex e
Ma
Z0 ~ 1G
Ex ia
Z1 ~ 2G
Ex d, Ex e, Ex px
Gb
high
Z2 ~ 3G
Ex nA, Ex pz
Gc
increased
Z20 ~ 1D
Ex ia, Ex ta
Da
very high
Z21 ~ 2D
Ex tb, pD, mD
Z22 ~ 3D
Ex tc, pD, mD
I
II
III
Gas groups:
IIA - Methane, ammonia, ethyl alcohol, etc.
IIB - Town gas, ethylene, hydrogen sulfide, etc.
IIC - Hydrogen, acetylene, etc.
Ingression protection to IP55 - dust protected and
water jets is standard for all types of Ex motors which
is equivalent to NEMA 3. IP56 - dust protected and
heavy seas are also common. Dust tight IP65 is
required for IIIC conductive dust and is possible for
roller bearing HV motors.
Level of
protection
M1
I
II
IIB gas group and T3 (200°C) temperature class
motors are by far the most common.
very high
Mb
high
Ga
very high
Db
high
Dc
increased
F.
Protection Classes
Electrical machines
Dust groups: (IP55)
IIIA - Combustible flyings
IIIB - Non-conductive dust
IIIC - Conductive dust (IP65)
Monitoring devices
Intrinsic safety (ia, ib)
Flameproof enclosure (d) > (db)
Pressurized apparatus (p)
Encapsulation (m)
Fig 3 Electrical Equipment Classification
Increased safety (e) >(eb)
In the Equipment Category designations M means
Mines, G means Gases and D means Dust. This
paper will only focus on the G Gases category.
Non sparking(nA)>(ec)
Regulation 94/9/EG ATEX,
European Norms, IEC- Norms
Fig 5 Classes of Protection
Electrical machines use different protection methods
than monitoring devices. However motors may have
installed monitoring devices that require separate
protection.
Classification of Gases and Vapours
Gas Groups
IIA (US Group D)
IIB (US Group C)
IIC (US Group A)
Ammonia,
methane, ethane
Town gas,
acrylonitrile
Hydrogen
Ethyl alcohol,
n-butane
Benzene,
n-hexane
Acetaldehyde
Ignition
temperature
G. Non Sparking “nA” in future “ec”
Permissible
temperature
class
> 450°C
T1
Max. 450°C
Ethylene, ethylene Ethyne
oxide
(acetylene)
> 300°C … ≤ 450°C
T2
Max. 300°C
Hydrogen sulfide
> 200°C … ≤ 300°C
T3
Max. 200°C
> 135°C … ≤ 200°C
T4
Max. 135°C
> 100°C … ≤ 135°C
T5
Max. 100°C
> 85°C … ≤ 100°C
T6
Max. 85°C
Ethyl ether
Carbon
disulfide
Powder filling (q)
Construction standards
In approximate terms the Explosion Protection Levels
(EPL) Ga, Gb, Gc correspond to the Equipment
Categories 1G, 2G and 3G which align with the Zones
0, 1 and 2. The latest IEC standards mean that nA
(non sparking) will become ec (for EPL increased zone 2); e (increased safety) will become eb (for EPL
high - zone 1) and d (flameproof) will become db (for
EPL high – zone 1). This terminology is mandatory
from 2018.
E.
Oil immersion (o)
Combustibility increases (maximum experimental
safe gap, minimum ignition energy becomes smaller)
Ex-protection
Construction
standards
Non
Sparking
EN
60079-0
60079-15
“nA“
(EN 50014
EN 50021)
Basic principle
Arcs and sparks are prevented during normal operation.
Maximum surface temperature does not exceed the
limits of temperature class.
“nA” will considered as “ec” in the future EN 60079-7
Installation
Equipment
protection level
Zone 2
Gc
Fig 6 Non Sparking Motor
Fig 4 Gases and Vapours Classification
According to EN 60079-15 this is an explosion
protection type in which the risk of ignition sources
occurring during normal operation is minimised by
utilising additional methods which can be:
Hydrogen is a very combustible gas but has a high
ignition temp. The higher the gas combustibility the
lower the Minimum Ignition Energy (MIE) and the
lower the Minimum Ignition Current (MIC) for intrinsic
safety circuits; and the smaller the Maximum
Experimental Safe Gap (MESG) for Ex d machines.
The higher the ignition temperature; the higher the
allowable surface temperature; and the lower the
permissible temperature class.
nA – non-sparking
nC – enclosed break
nL – limited energy
nR – restricted breathing
2
nA is the most appropriate method of protection for
electrical machines. In future nA (non sparking) will
become ec for Equipment Protection Level (EPL) increased - zone 2. That is Ex n motors can only be
used in zone 2.
A flameproof motor must fulfil three prime
requirements. Firstly the design must limit the outside
surface temperature not to exceed the permitted
temperature class. Secondly the explosion resistance
must ensure that an explosion cannot spread to the
external surroundings. Lastly the pressure resistance
prevents any lasting damage or deformation to the
protection of the motor following explosions within the
enclosure.
A rotor design ignition risk assessment is required for
Ex n motors >100kw and other than S1 or S2
operating modes. A stator winding ignition risk
assessment is required for motors >1kV and other
than S1 or S2 operating modes. (EN 60079-15)
Basic principle
Ex d motors typically can handle up to a T4
temperature class and with special designs even T5
and T6 can be achieved. In future d (flameproof) will
become db for EPL high – zone 1.
Equipment is designed
to prevent hazardous temperatures,
sparks and arcs during normal operation.
Ignition during breakdown is prevented by additional
mechanical, electrical and thermic safety measures.
An Ex d motor may have withstood many internal
explosions during its’ lifetime without affecting
operation.
H. Increased Safety “e” in future “eb”
Ex-protection
Construction
standards
Increased
safety
EN
60079-0
60079-7
“e“
(EN 50014
EN 50019)
Installation
Equipment
protection level
Zone 1
Gb
Zone 2
Gc
J.
Ex-protection
Pressurised
“px“
“py“
“pz“
Pressurized Apparatus “p”
Construction
standards
EN
60079-0
60079-2
(EN 50014
EN 50016)
Basic principle
All parts capable of igniting flammable gases are
placed inside an enclosure,
pressurized by a protective gas (min. 0.5bar).
The surrounding atmosphere
cannot enter during operation.
Fig 7 Increased Safety Motor
Installation
Ex e motors are always de-rated to prevent
hazardous temperatures, sparks and arcs during
normal operation including start-up. This de-rating
makes Ex e motors unpopular and not widely used. In
addition Ex e motors typically can only handle a T3
temperature class.
In future e (increased safety) will become eb for EPL
high - zone 1.
Ex-protection
EN
Flameproof 60079-0
60079-1
“d“
(EN 50014
EN 50018)
Gc
Leakage Loss Compensation is generally used for
electrical machines rather than a continuous purge.
Flameproof “d” in future “db”
Construction
standards
Gb
Fig 9 Pressurized Motor
The “px” system where a pressurised enclosure which
reduces the device protection level inside the
pressurised enclosure housing from Gb (zone 1) to
“not at risk of explosions” is the most common. The
“py” system is not suitable for motors and the “pz”
method can be used for zone 2 but is not popular.
A stator winding ignition risk assessment is required
for motors >1kV. (EN 60079-14) also anticondensation heaters must be fitted and additional
protection during start-up maybe required (purging,
measure gas concentration etc.)
I.
Equipment
protection level
Zone 1
Zone 2
K. Protection Comparison for Low Temps
Basic principle
LV-Motors
All parts capable of igniting flammable gases
are placed inside a flameproof enclosure.
An explosion inside is not propagated outside
the enclosure.
The outer parts of the flameproof enclosure
do not exceed permissible surface temperatures.
HV-Motors
Ex nA
Ex e
Ex d
+
+
o
Low temperatures
Ex nA
Ex e
Ex d
Ex px
+
+
o
o
BVS 11 ATEX E 084 X
Installation
Equipment
protection level
Zone 1
Zone 2
Gb
Gc
w
The range of ambient temperatures is 40°C down to -20°C. This
temperature range may be extended to 60°C down to -40°C with a
special electrical or thermal design in which suitable terminal
boxes, materials and components are used, or with the data for the
electrical ratings.
L
Fig 10 Low Temp Protection Comparison
Fig 8 Flameproof Motor
3
Motors in all explosion protection types are available
for low temperatures down to -40°C and below.
However, often supplementary measures must be
utilized for low temperature operation. It should also
be noted that at low temperatures, the strength values
of the motor materials decrease, especially plastics.
L. Protection Comparison for Inverter Use
LV-Motors
prevent the outside
temperature class limit.
Ex e
Ex d
o
-
++
Inverter operation
Ex nA
Ex e
Ex d
Ex px
o
-
++
+
the
HV-Motors
Ex nA
Ex e
Ex d
o
-
+
Ex nA
Ex e
Ex d
Ex px
o
-
+
-
Monitoring investment
w
L
Additional effort for testing and certification
Thermal sole
protection means
that the PTC is the
ONLY temperature
protection device.
Ex nA -Motor
DOL-operation:
Motor protection switch
and/or thermal
monitoring
Ex e-Motor
DOL-operation:
certified motor prot.
Switch with Is/Ir-tE-timecurve and/or thermal
monitoring
Inverter operation:
thermal monitoring by
LV-PTC‘s / HV– PT100
thermal sole protection
test required
HV with anti-cond. heater
Inverter operation:
thermal monitoring by
LV-PTC‘s / HV– PT100
certified thermal sole
protection test required
HV with anti-cond. heater
Ex p-Motor
DOL-operation:
Motor protection switch
and/or thermal monitoring
plus Ex p -monitoring
Ex d-Motor
DOL-operation:
Motor protection switch
and/or thermal
monitoring
Inverter operation:
thermal monitoring by
LV-PTC‘s / HV– PT100
thermal sole protection
test required
Inverter operation:
thermal monitoring by
LV-PTC‘s / HV– PT100
plus Ex p -monitoring
thermal sole protection
test required
Fig 12 Monitoring Investment Comparison
* dependent on
x
exceeding
LV-Motors
HV-Motors
Ex nA
surface
inverter type,
counter torque
characteristic and
speed range
M. Protection Comparison by Weight
LV-Motors
Fig 11 Inverter Use Protection Comparison
Non-sparking machines must, as a minimum, first be
type tested as a system with the actual inverter to be
used or a comparable one. For Ex nA it must be
ensured that the permissible inner as well as outer
temperature does not exceed the temperature class
limit during operation, particularly at low speeds when
the cooling fan may also be running slowly.
HV-Motors
Ex nA
Ex e
Ex d
++
o
-
Weight
Weight comparison for LV motors
KG/KW
22.5
Ex e
Ex d
Ex px
++
-
-
++
Weight comparison for HV-motors
KG
18000
20.0
Ex nA - 1PS1
Ex e - 1PS2
Ex d - 1PS5
17.5
15.0
12.5
16000
Ex nA - 1PS1
14000
Ex e - 1PS2
Ex d - 1PS5
12000
Ex px - 1PS6
10000
10.0
8000
7.5
6000
5.0
Ex e motors must always be tested and certified as a
complete system together with the actual inverter to
be used (the only exception is PTB certification with
significant power de-rating – taking into account the
thermal reserves – and only for a square law load
torque).
Ex nA
4000
2.5
2000
0.0
90 100 112 132 160 180 200 225 250 280 315
0
250kW
Shaft height
710kW
1250kW
4000kW
Fig 13 Weight Protection Comparison
Ex nA and Ex p motors have the lowest weight.
Generally Ex e motors with the same power rating are
at least one or two frame sizes larger (especially for 2
and 4-pole motors) and are therefore heavier. The
higher the power rating, the more significant the
differences in the corresponding shaft heights.
Ex p motors can always be operated with an inverter.
However if the purge system fails it must be ensured
that the inner temperatures do not exceed the
permissible temperature class limit. This also applies
to mounted/installed components, for example heating
systems.
Generally, an Ex d motor has the same active part as
an Ex nA or Ex p motor. However, the enclosure and
the end shields are significantly bigger and therefore
also heavier as they must withstand high explosion
pressures.
N. Protection Comparison for Large Power
For all Ex e, Ex nA and Ex p motors, the permissible
inverter must be specified on the certificate, and the
necessary tripping device on the manufacturer's
declaration or on the Ex certificate.
LV-Motors
The inner components of Ex d motors e.g. heating
system, do not generally require an Ex version. The
installed temperature sensors are selected and
located so that they trip earlier before the motor
surface reaches the temperature limit. This is the
reason that other inverters can be used with Ex d
motors, assuming that the company operating the
drive system complies with the regulations specified
by the motor manufacturer.
HV-Motors
Ex nA
Ex e
Ex d
o
-
o
Large power rating
Ex nA
Ex e
Ex d
Ex px
++
--
o
++
Output power limits 6kV/50Hz air cooled.
kW
12000
10000
8000
Ex nA
Ex e
6000
Ex d
4000
Ex px
2000
Thermal sole protection test means that the
temperature sensor trip (PTC in winding) is tested
because it is the sole (only) means of protection to
0
2-pole
4-pole
6-pole
8-pole
Fig 14 Large Power Protection Comparison
4
HV Ex d motors, as a result of the necessary
explosion protection, can only have higher power
ratings in IC511/IC516 (tube cooling, tubes
concentrically arranged around the stator core); a
mounted cooler is not possible. 1000mm is the
maximum shaft height that can still be tested in the
worlds largest Ex d test laboratory. As a
consequence, the maximum power for a 4-pole motor
with 6kV is approx. 8 MW.
P.
Protection Comparison by Ops Costs
LV-Motors
HV-Motors
Ex nA
Ex e
Ex d
+
++
+
o
-
++
Flexibility for applications
92.0%
96.0%
90.0%
88.0%
84.0%
95.5%
Ex nA / Exd / Ex p
Ex e - 1PS2
95.0%
Ex e - 1PS2
94.5%
80.0%
94.0%
78.0%
3kW
55kW
250kW
250kW
710kW
710kW
1250kW
4000kW
Fig 16 Ops Costs Protection Comparison
As a result of the lower thermal utilization, an Ex e
motor has lower copper losses, and therefore in
comparison, a higher efficiency.
For Ex p motors, the costs associated with the
purging air supply (purchase, installation and
operating costs) is an additional cost, which
depending on the motor size and bearing design, can
amount to several thousand Euros per year.
Ex nA
Ex e
Ex d
Ex px
o
-
++
+
Q. Protection Comparison Summary Table
LV-Motors
Ambient
temperatures
Process
reliability
Ex nA / Ex d / Ex p
82.0%
DOL /
Inverter
operation
independent
installation
-
96.5%
94.0%
HV-Motors
Ex d
+
97.0%
96.0%
O. Protection Comparison for Flexibility
Ex e
Ex px
++
97.5%
98.0%
When it comes to higher power ratings, there are no
restrictions for Ex nA and Ex p motors.
LV-Motors
Ex d
+
Comparison of efficiency for HV-Motors
100.0%
86.0%
Ex nA
Ex e
Operational costs
Comparison of efficiency for LV-Motors
2 and 4 pole Ex e motors, with power ratings above
approx. 2.5 MW are no longer practical because
achieving a reasonable (long) safe locked rotor time
(te) it is necessary to reduce the starting current,
which leads to a low starting torque.
Ex nA
Applications
Duty types
Fig 15 Flexibility Protection Comparison
Ex d motors have the best flexibility, because in
principle, they can be designed for normal line
operation, intermittent duty, inverter operation as well
as heavy-duty starting. For an Ex nA motor,
intermittent duty is no longer considered normal
operation; as a consequence, starting must also be
taken into account in the explosion protection
assessment, which makes it similar to an Ex e motor.
HV-Motors
Ex nA
Ex e
Ex d
-++
o
o
o
+
+
o
o
o
++
o
o
+
o
++
++
o
+
o
++
o
++
++
++
+
+
++
+
++
+
o
++
+
o
Ex nA
Ex e
Ex d
Ex px
-++
o
o
o
+
+
o
o
o
++
++
o
+
o
++
++
o
+
-++
o
++
+
++
+
o
++
+
++
+
o
++
+
o
++
++
o
o
+
o
++
+
+
++
++
+
-
Operation in Zone 1 – Gas/Vapors
Gas group ((IIA, IIB, IIC)
Temperature class (T3-T6)
Dust ignition proof
Ability for corrosive cooling medium
Low temperatures
Overload operation
Heavy duty starting
Inverter operation
Monitoring investment
Weight
Large power rating
Flexibility for applications
Operational costs
Maintenance costs
Comparison based on experience from Service and Engineering information
Fig 17 Comparison Summary Table
Evaluation Key
++
Very well suited
+
Well suited
0
Suited
Less suited
-Not suited
Intermittent duty is only possible for an Ex p motor if it
is continually purged (also at standstill).
R. Cost Comparison
An essential advantage of Ex d high-voltage motors,
when compared to Ex p and Ex e motors (which must
be purged before starting) is that following a power
failure or after the motor has been switched off, it can
be immediately restarted.
6kV / 50Hz – 1500rpm - AT -20/+40°C, air cooled
150%
Ex nA (1PS1)
Ex e (1PS2)*
Ex d (1PS4)
Ex px (1PS6)
140%
130%
120%
110%
100%
90%
300kW
800kW
1600kW
Fig 18 Cost Comparison
5
2500kW
5000kW
Ex na motors are always the most cost effective but
are only suitable for zone 2 operation. Ex e motors
are always expensive because they are de-rated. Ex
p are the most expensive when small but become
cheaper the bigger the motor size because the purge
system becomes less as a proportion of the total
motor cost. Ex d becomes the most expensive as the
explosion proof enclosure becomes a larger
proportion of the total motor cost.
S.
[3] EN 1127-1:2011 Explosive atmospheres.
Explosion prevention and protection. Basic concepts
and methodology
[4] Directive 2014/34/EU Equipment for potentially
explosive atmospheres (ATEX)
[5] EN 60079-1:2014. Explosive atmospheres.
Equipment protection by flameproof enclosures "d".
[6] EN 60079-2:2014. Explosive atmospheres.
Equipment protection by pressurized enclosure "p".
[7] EN 60079-7:2015. Explosive atmospheres.
Equipment protection by increased safety "e"
[8] EN 60079-15:2010. Explosive atmospheres.
Equipment protection by type of protection "n".
[9] EN 60079-14:2014. Explosive atmospheres.
Electrical installations design, selection and erection
[10] Barata et al. “Flameproof Motors operating in the
Artic Circle without the need for preheating” PCIC
Europe Conference Record, BER-61 2016.
[11] Munro et al. “Are the IEC requirements for
overpressure testing of Ex d equipment appropriate?”
PCIC Europe Conference Record, BER-41 2016.
[12] Mistry et al. “What is new in next edition of IEC
60079-7 standard of Ex e motors?” PCIC Europe
Conference Record, LO-109 2015.
[13] Neleman et al. “Motor Controls for Ex Motors in
Hazardous Areas: An Application Guide” PCIC
Europe Conference Record, BA-06 2009.
Info required for Ideal Motor Selection
Certification
Norm
Installation
Country
e.g.: Gost /
Russia
Driven
Equipment
e.g..: Pump
Mg ~ n²
Operation
mode
e.g. DOL or
Inverter
overload
duty cycle
Zone, Gas
group
Temperature
-class
e.g.: IIC T4
Cooling
temperature
altitude
e.g.
-45/+40°C
1000m
Starting
conditions
e.g. 3/2
cold/hot
80% RV
Required
cooling type
e.g. IC411,
IC511,
IC81W etc.
Fig 19 Motor Selection Info Required
VI.
It is easier to optimise the proposed motor/drive
solution when more information can be specified at
the quotation stage.
III.
Dipl.-Ing Hugo Stadler
Hugo Stadler graduated from the Fachhochschule
Regensburg with an Electrical Engineer Dipl.-Ing.
(FH). After six years in the development department
for variable speed drives at SIEMENS (Loher) he
moved into the sales department and served key
customers in the Oil & Gas and Chemical industry.
Hugo’s competence is electrical motors, frequency
inverters and ex-protection with over 40 years service
and experience with the SIEMENS (Loher) company.
Today Hugo Stadler is responsible for the SIEMENS
sales of LV drive systems to the Oil & Gas industry.
CONCLUSION
Flameproof Ex d motors provide the best flexibility
across LV and HV ranges; they can also be used with
any manufacturer’s inverter without special testing.
However, Ex d motors become increasingly expensive
& heavy with a maximum limit of circa 8MW, so Ex p
is better for larger sizes.
IV.
Eur Ing Steve Jackson MA BSc CEng
ACKNOWLEDGEMENTS
Steve Jackson graduated from the University of Bath
Chemical Engineering School with a BSc (Hons) in
1982. During 2016 he enhanced his academic
qualifications with a Masters in Sales Management
from the University of Portsmouth. In 1987 Steve
became a Chartered Engineer and in 1994 a
European Engineer. He has been a Member of the
Institute of Measurement and Control for nearly 30
years. Over the course of his career Steve has
worked for Fisher Controls, Elsag Bailey, ABB,
Endress+Hauser and for the last 12 years SIEMENS
– in the fields of automation, instrumentation, process
analytics and electrical engineering. Steve is also a
committee member for the Energy Industries Council
(EIC).
The authors acknowledge the contributions made to
this paper over the years by such hazardous area
motor luminaries as Helmut Hasch, Karl Hofbauer,
Klaus Neupert, Thomas Mutzl, Thomas Fuchs and
Ulrich Schanzer.
V.
VITA
REFERENCES
[1] Siemens Loher, Ruhstorf Explosion proof drives –
Planning and Engineering Course: DR-EX-PL
[2] Siemens ABC of Motors Manual – October 2009
6
VII.
APPENDIX Enlarged Figures
Directive 94/9/EC
Equipment Equipment
group
category
EPL
Types of protection Equipment
Equipment
Examples
group
Protection Level
M1
Ex ia
M2
Ex d, Ex e
Z0 ~ 1G
Ex ia
Z1 ~ 2G
Ex d, Ex e, Ex px
Z2 ~ 3G
Level of
protection
Ma
very high
Mb
high
Ga
very high
Gb
high
Ex nA, Ex pz
Gc
increased
Z20 ~ 1D
Ex ia, Ex ta
Da
very high
Z21 ~ 2D
Ex tb, pD, mD
Db
high
Z22 ~ 3D
Ex tc, pD, mD
Dc
increased
I
II
EN 60079-0
I
II
III
Dust groups: (IP55)
IIIA - Combustible flyings
IIIB - Non-conductive dust
IIIC - Conductive dust (IP65)
Gas groups:
IIA - Methane, ammonia, ethyl alcohol, etc.
IIB - Town gas, ethylene, hydrogen sulfide, etc.
IIC - Hydrogen, acetylene, etc.
Fig 3 Electrical Equipment Classification
LV-Motors
HV-Motors
Ex nA
Ex e
Ex d
o
-
++
Inverter operation
Ex nA
Ex e
Ex d
Ex px
o
-
++
+
Additional effort for testing and certification
Thermal sole
protection means
that the PTC is the
ONLY temperature
protection device.
* dependent on
x
Fig 11 Inverter Use Protection Comparison
7
inverter type,
counter torque
characteristic and
speed range
LV-Motors
HV-Motors
Ex nA
Ex e
Ex d
++
o
-
Ex nA
Ex e
Ex d
Ex px
++
-
-
++
Weight
Weight comparison for LV motors
KG/KW
22.5
Weight comparison for HV-motors
KG
18000
20.0
Ex nA - 1PS1
Ex e - 1PS2
Ex d - 1PS5
17.5
15.0
12.5
Ex nA - 1PS1
16000
Ex e - 1PS2
14000
Ex d - 1PS5
12000
Ex px - 1PS6
10000
10.0
8000
7.5
6000
5.0
4000
2.5
2000
0.0
90 100 112 132 160 180 200 225 250 280 315
0
250kW
Shaft height
710kW
1250kW
4000kW
Fig 13 Weight Protection Comparison
LV-Motors
HV-Motors
Ex nA
Ex e
Ex d
-++
o
o
o
+
+
o
o
o
++
o
o
+
o
++
++
o
+
o
++
o
++
++
++
+
+
++
+
++
+
o
++
+
o
Operation in Zone 1 – Gas/Vapors
Gas group ((IIA, IIB, IIC)
Temperature class (T3-T6)
Dust ignition proof
Ability for corrosive cooling medium
Low temperatures
Overload operation
Heavy duty starting
Inverter operation
Monitoring investment
Weight
Large power rating
Flexibility for applications
Operational costs
Maintenance costs
Ex nA
Ex e
Ex d
Ex px
-++
o
o
o
+
+
o
o
o
++
++
o
+
o
++
++
o
+
-++
o
++
+
++
+
o
++
+
++
+
o
++
+
o
++
++
o
o
+
o
++
+
+
++
++
+
-
Comparison based on experience from Service and Engineering information
Fig 17 Comparison Summary Table
Fig 20 Gas Hazard Marking – in future the EPL will be added to the end eg ‘……………Ex d IIC T4 Gb’
8
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