ATEX / IEC Terminology SB568 ATEX / IEC Motor Terminology
Alleinshutz
Alleinshutz defines the certification of flameproof motor and protection device together. In the IEC world
the most common protection device is a thermistor and relay that is set to switch off the motor in case of
overheating before any danger of explosion can occur, unlike North America where the practice is to use
a thermostat.
Ambient Temperature
Ambient temperature is the temperature that surrounds the motor. Ambient is always based on
nameplate KW. It is common practice to reduce the nameplate KW to accommodate the higher ambient.
Altitude
IEC identifies 1,000 meters as standard where NEMA would be 3,300 feet. NEMA defines a maximum
altitude of 16,500 feet; IEC defines a maximum altitude of 4,000 meters. IEC 34-16.3.5 specifications
assume that reduced cooling will occur as a result of higher altitude and is compensated by a reduction of
the maximum ambient temperature per the table below:
Altitude
In Meters
1000
2000
3000
4000
Temperature (C)
Class of Insulation
F
40
30
19
9
B
40
32
24
16
H
40
28
15
3
ATEX 95
This directive sets out the essential health and safety requirements (EHSR) for equipment and protection
systems intended for use in potentially explosive atmospheres. Refer to ATEX Directives definition for
additional comments.
ATEX 137
ATEX Directive 137 is actually an addendum to ATEC Directive 95. ATEX Directive 95 describes the
construction of equipment intended for installation and use in potentially explosive atmospheres and
ATEX Directive 137 describes how these areas should be classified into hazardous areas and how work
can be performed safely in these areas.
ATEX Directives
ATEX is an abbreviation for the French “ATmosphere EXplosible” and is used as a synonym for the two
European directives related to explosion hazard in atmospheric conditions.
ATEX 95 Directive specifies the construction of equipment and protection systems intended for use in
potentially explosive atmospheres.
ATEX 137 Directive specifies to the use of equipment and protection systems intended for use in
potentially explosive atmospheres.
ATEX Group
Two groups are referred to in the ATEX 95 Directive: Group I and Group II. Both groups are further
subdivided into categories. These categories indicate whether a device or protective system can be
deployed in a possible explosive atmosphere with gas (G), mist, with dust (D) or with gas and dust (GD).
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ATEX / IEC Motor Terminology
Group I
Comprises equipment intended for use in the underground parts of mines and to those parts of surface
installations of such mines likely to be exposed to combustible dust.

Category M1
Products of this category are required to remain functional for safety reasons when an explosive
atmosphere is present and is characterized by integrated explosion protection measures
functioning in such a way that:
 In the event of failure of one integrated measure, at least a second means of protection
provides for a sufficient level of safety, or
 In the event of two faults occurring independently of each other, a sufficient level of safety is
ensured.

Category M2
These products are intended to be de-energized in the event of an explosive atmosphere.
Group II
Comprises equipment intended for use in other places likely to become endangered by explosive
atmospheres.

Category 1
Comprises products designed to be capable of remaining within its operational parameters,
stated by the manufacturer, and ensuring a very high level of protection for its intended use in
areas in which explosive atmospheres caused by mixtures of air and gases, vapors, mists of
air/dusts mixtures are highly likely to occur and are present continuously, for long periods of time
or frequently.

Category 2
Comprises products designed to be capable of remaining with their operational parameters,
stated by the manufacturer, and based on a high level of protection for their intended use, in
areas in which explosive atmospheres caused by mixtures of air and gases, vapors, mists or
air/dust mixtures are likely to occur.

Category 3
Comprises products designed to be capable of keeping within its operational parameters, stated
by the manufacturer, and based upon a normal level of protection for its intended use,
considering areas in which explosive atmospheres, mists or air/dust mixtures are unlikely to occur
and if they do occur, do so infrequently and for a short period of time only.
Atmosphere
The environmental atmosphere and prevailing conditions at the workplace are a major determinant for the
installation methods of equipment and the choice of materials to be used. It is, therefore, a prerequisite to
classify the areas with potential gas and dust explosive atmospheres into hazardous areas.
The potentially hazardous areas are classified into hazardous areas based on the frequency and duration
of the occurrences of an explosive atmosphere.
Zone 0, 1 and 2: Areas at risk of gas explosion (where a mixture of air with any combination of flammable
gas, fumes or mist is present).
Zone 20, 21 and 22: Areas at risk of dust explosion (where a cloud of flammable dust may occur).
The lowest number indicates the lowest hazardous area.
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ATEX / IEC Motor Terminology
BASEEFA
The abbreviation for British Approval Service for Electrical Equipment. BASEEFA is a third party
independent testing and certification agency. This is one agency that can be used to obtain third party
certification for motors in hazardous areas.
B3 Mount
Mounting arrangement with the motor base mounted with the shaft in the horizontal plane. Similar to F2
mount in NEMA terminology.
B5 Mount
Mounting arrangement with the motor flange at the drive end and no base with the shaft in the horizontal
plane. This would be close to a NEMA motor with a D-Flange.
B14 Mount
Mounting arrangement with the motor flange at the drive end and no base with the shaft in the horizontal
plane. This would be similar to a NEMA motor with a C-Face.
NOTE: IEC only defines two flanges “FF” where the bolt holes are thru-bolts and “FT” which the bolt
holes are tapped or threaded. NEMA defines what size D-flange or C-face will be standard on what
frame, IEC does not define what size flange will be on what frame and leaves it up to the motor
manufacturer to define this to IEC 72 dimensions. A flange is defined by the “FF” or “FT” followed by the
bolt circle dimension “M” in millimeters. For example a frame designation would be written as 200L FF280
which defines the FF as thru-bolt hole construction with a 280 mm bolt circle.
Cable Gland
A cable connection device that is used on a jacketed neoprene cable. The cable gland screws into the
motor conduit box and a compression seal bushing fits around the incoming cable, that when
compressed, seals around the cable jacket. The result is a liquid or a dust tight connection.
Products in this category are required to remain functional for safety reasons when an explosive
atmosphere is present and is characterized by integrated explosion protection measure functioning in
such a way that:
 In the event of failure of one integrated measure, at least a second means of protection provides
for a sufficient level of safety, or
 In the event of two faults occurring independently of each other, a sufficient level of safety is
ensured.
CENELEC
The European Committee for Electrotechnical Standardization is a standards writing organization. It was
established by the European Union to develop harmonized electrical standards for European countries.
CE Mark
Conformity European, or CE, is an administrative identification meant to be a reference for trade
authorities showing that the identified product satisfies the requirements of the technical harmonization
guidelines. Beginning in January 1997 any motor labeled as such requires a manufacturer to have
established a technical construction file and be able to issue a Declaration of Conformity upon request
that it meets the European Standards for Safety and environmental protection.
D-End
Abbreviation for drive end bearing.
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ATEX / IEC Motor Terminology
DSEAR
The Dangerous Substances and Explosive Atmospheres Regulations of 2002) is the United Kingdom’s
implementation of the European union-wide ATEX Directive. The intention of the regulation is to reduce
the risk of a fatality or serious injury resulting from a “dangerous substance” igniting and potentially
exploding. Examples of a “dangerous substance” as defined by SDEAR include sawdust, ethanol vapors
and hydrogen gas. The regulation is enforceable by HSE or lower authorities.
Design Code
IEC has only two definitions for Electrical Design Characteristics, Design N and Design H whereas NEMA
has four Designs. Design N is a motor with a normal torque curve similar to a NEMA Design B. Design
H is a motor with a high starting torque similar to a NEMA Design C or NEMA Design A. No limit is set for
how high of starting torque is required for a motor to be labeled Design H. So if you have a specification
calling for a Design H you will need to get a clear understanding of the torque requirements, starting and
breakdown torque. NOTE: There is no cross-reference from NEMA Design D to IEC.
DIN
An abbreviation for Deutsche Industrie Normenasusschvs. DIN is the association in Germany that
determines the standards for electrical and other equipment in that country.
Directive
A directive is a legislative act of the European Union, which requires member states to achieve a
particular result without dictating the means of achieving that result. It can be distinguished from
regulations which are self-executing and do not require any implementing measures.
Directive 94/9/EC
The European Union directive to protect people from explosion risk in areas with an explosive
atmosphere. Refer to ATEX 95 and ATEX Directives and Definitions, for additional comments.
DNV
DNV is an abbreviation for Det Norske Veritas. DNV is a Commercial Marine Specification Organization
that is similar to and competes with American Bureau for Shipping (ABS). DNV commercial marine
specifications do not require that an IEC motor meet the specifications although you will see DNV most
commonly used with IEC motors.
Dust Ignitionproof
Dust ingnitionproof motors are used in atmospheres where combustible dust is present.
Duty Cycle
The duty cycle types are indicated by the symbols S1 through S9 according to IEC34.1. See the table
below.
Duty Type
S1
S2
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Short Description
Continuous Duty
Explanation
Operation at constant load of sufficient duration for
thermal equilibrium to be reached. - Similar to the
NEMA definition of Continuous Duty.
Operation at constant lad during a given time, less
than that required to reach thermal equilibrium,
followed by a rest and de-energized period to
established motors ambient level. Similar to NEMA
15 minute or 30 minute duty motors.
Short-Time Duty
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ATEX / IEC Motor Terminology
S3
Intermittent Duty without
influence of running-up period
S4
Intermittent Duty with influence
of running-up period
Intermittent Duty with influence
of running-up period and
electrical braking
Continuous Operation Periodic
Duty
S5
S6
S7
A sequence of identical duty cycles each including a
period of operation at constant load and a rest and
de-energized period. The starting current does not
significantly affect the temperature rise.
Same as S3 but with each cycle including a
significant period of starting.
Same as S4, but with each cycle, including a period
of rapid electric braking.
A sequence of identical duty cycles, each cycle
consisting of a period of operation at constant load
and a period of operation at no-load. There is no rest
and de-energized period.
Same as S6 with each cycle including a period of
starting and a period of electric braking.
As S6 with each cycle,
including a period of starting
and a period of electric
braking.
Effective Ignition Source
Effective ignition source is a term defined in the European ATEX Directive as an event which, in
combination with sufficient oxygen and fuel in gas, mist, vapor or dust form, can cause an explosion.
Methane, hydrogen or coal dust are examples of possible fuels.
Effective ignition sources are lightning strikes, open flames, mechanically generated impact sparks,
mechanically generated friction sparks, electric sparks, high surface temperatures, electrostatic
discharge, radiation and adiabatic compression.
Enclosure
The enclosure field in IEC is a combination of the IP (Inherent Protection) and IC (Inherent Cooling)
codes. Each number in the IP code or the IC code stands for a different degree of protection. The first
number in the IP code refers to contact with live or moving parts inside the enclosure and the ingress of
solid objects entering the motor. The second number has to do with degree of protection or ingress of
liquids into the motor enclosure.
NOTE: IEC defines the IP codes by type enclosure of product in different sections. IEC 34-5 applies to
motors or rotating products.
IP Code per IEC 34-5
First
Numeral
0
1
2
3
4
5
6
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Degree Protection
Protection of Persons
Ingress of Solids
No special protection
No protection
Protection of large surface of body (e.g. a
No ingress of solid objects larger than 50
hand)
mm diameter
Prevention of contact by finger
No ingress of solid objects larger than 12
mm diameter
Does not apply to rotating machines
Does not apply to rotating machines
Objects of thickness greater than 1 mm
No ingress of solid objects larger than 1
mm, excluding ventilation openings and
drain holes
Complete protection
No amounts of dust that interferes with
satisfactory operation of the motor.
Does not apply to rotating machines
Does not apply to rotating machines
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ATEX / IEC Motor Terminology
Second Numeral
0
1
2
3
4
5
6
7
8
Degree of Protection
No special protection
Vertically falling drops shall have no harmful effect
Drops falling at any angle up to 15 from vertical shall have no harmful effect.
A spray falling at any angle up to 60 from vertical shall have no harmful effect.
A splash from any direction shall have no harmful effect.
Liquid projected by a nozzle from any direction shall have no harmful effect.
Water from heavy seas or powerful water jets shall not enter in harmful amounts.
When machine is immersed for the time and depth stated in test conditions,
harmful amounts of water shall not enter.
When machine is immersed to the pressure agreed on between manufacturer
and customer for an indefinite time, harmful amounts of water shall not enter.
A letter “S”, “M” or “W” may follow the second numeral of the IP code.
“S” indicates that the machine was tested against the ingress of liquids with the machine not running.
“M” indicates that the machine was tested against the ingress of liquid with the machine running. If neither
“S” nor “M” is used, the machine was tested both running and not running.
“W” indicates a weather-protected machine. This protection is that under prescribed conditions; rain,
snow and airborne particles will not enter the machine in harmful amounts.
First Numeral
0
1
2
3
4
5
6
7
8
9
Second Numeral
0
1
2
3
4
5
6
7
8
IC Code per IEC 34-6
Method of Cooling
Free Circulation
Inlet pipe ventilation
Outlet pipe ventilated
Inlet and Outlet pipe ventilated
Frame Surface Cooled
Integral mounted heat exchanger
Machine mounted heat exchanger
Integral heat exchanger transferring heat to a piped in medium
Machine mounted heat exchanger transferring heat to a piped in medium
Separately mounted heat exchanger transferring heat to a piped in medium
Source of Power to Circulate Coolant
Free Convection
Self Circulate
Integral component mounted on separate shaft
Dependent component mounted on the machine
(not used)
Integral independent component
Independent component mounted on machine
Independent and separate device or coolant system pressure
Relative displacement
Enclosure Conversation Table
IEC Enclosure
NEMA Enclosure
ODP
IP23IC01
TENV
IP54IC40
TEFC
IP54IC41
TEAO
IP54IC48
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ATEX / IEC Motor Terminology
EN
Euronorm (EN) is a standards writing organization.
EX Mark
The EX mark is the European Commission mark for products approved for hazardous areas.
EX d
The EXd type of protection is the only type of protection based on containment of the explosion. The
electrical components that could ignite an explosive atmosphere are located inside an enclosure which
can withstand the pressure of an explosion of the explosive mixture which has formed inside due to the
penetration of a flammable gas or vapor. The enclosure must also prevent the transmission of the
explosion to the explosive atmosphere surrounding the enclosure (flameproof).
EX de
The EX de protection is a combination of “d” flameproof protection and “e” protection.
EX e
The EX e protection applies to the electrical equipment which does not product arcs, sparks or hazardous
temperatures under normal operation (non-sparking construction).
EX nA
The EX nA type of protection applies to the “non-sparking” requirement, i.e. equipment which does not
provide arcs, sparking or hazardous temperatures under normal operation.
EX tD
The EX tD type of protection is based on the protection by an enclosure which is sealed to the penetration
of dust and limits the surface temperature.
Explosive Atmosphere
An explosive atmosphere is defined as a mixture of dangerous substances with air, in the form of gases,
vapors, mist or dust in which, after ignition has occurred, combustion spreads to the unburned mixture.
Atmospheric conditions are commonly referred to as ambient temperatures and pressures. Temperatures
of -20°C to 40°C and pressures of 0.8 to 1.1 bar.
Flameproof – Type of Protection “d”
Since flammable gases and vapors are expected inside an enclosure, the equipment must be capable of
withstanding an explosion caused by sparking contacts of devices, high temperatures or an electrical
fault. The enclosure is designed so hot gases generated during an internal explosion are cooled below
the ignition temperature of the surrounding flammable atmosphere as they escape through the joints of
the unit.
In addition, the external surfaces of the enclosure must not become hot enough to ignite the surrounding
atmosphere due to heat energy within the unit. This heat energy may be the result of normal operation of
heat-producing equipment, or the result of an electrical arc to the enclosure from an arcing ground fault.
Safety factors are applied to all testing of this type of enclosure to ensure the unit will not rupture as a
result of an internal explosion.
Frame
The IEC specification 72 uses metric frame measurements. An IEC frame 112S or 112M or 112L
denotes a 112 mm shaft height. The S, M, or L stands for Small, Medium, and Long. NOTE: IEC frames
280K and 280H are not defined by IEC specification 72 but are recognized and used throughout the IEC
industry.
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ATEX / IEC Motor Terminology
IEC Frame
71M
80M
90S
90L
100S
100L
112S
112M
112L
132S
132M
132L
160S
160M
160L
180S
180M
180L
200S
200M
200L
225S
225M
225L
250S
250M
250L
280S
280M
280K
280H
“H” Shaft Height
in mm
71
80
90
90
100
100
112
112
112
132
132
132
160
160
160
180
180
180
200
200
200
225
225
225
250
250
250
280
280
280
280
Nearest
NEMA Frame
48
56
56
56
140
140
180
180
180
210
210
210
250
250
250
280
280
280
320
320
320
360
360
360
400
400
400
444
445
447
449
Hazardous Area
Hazardous areas are defined as premises, buildings or parts of the where fire or explosion hazards may
exist due to the presence of flammable gases or vapors, flammable liquids, combustible dusts or easily
ignitable fibers or flyings.
IEC defines the classification of hazardous areas into three zones, according to degree of hazard.
Where ignitable concentrations of flammable gases, vapors or liquids are present
Zone 0
continuously or for long periods of time under normal operating conditions.
Where ignitable concentrations of flammable gases, vapors or liquids are likely to
Zone 1
exist under normal operating conditions.
Where ignitable concentrations of flammable gases, vapors or liquids are not likely to
Zone 2
exist under normal operating conditions.
NOTE: An IEC document recommends that no rotating apparatus should be located in a Zone 0 area.
IEC defines Classification of Gases: IEC uses a Group code as a location code and an Alpha Code as
a Gas Type:
Group I - Coal Mines
Group II - Other Industries
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ATEX / IEC Motor Terminology
IEC
A
B
C
NEC
Group D
Group C
Groups A, B
IEC Designation
Flameproof - noted as (EXd)
Pressurized – noted as (EXp)
Increased Safety – noted as (Exe)
Gas Examples
Gasoline, Methane, Natural Gas
Ethyl, Ether
Acetylene, Hydrogen
USA & Canada Equivalent
UL /CSA listed Explosion Proof
UL/CSA listed Purged
Non-Sparking motor with:
1. Permissible temperature rise reduced by 10C for
all insulation types.
2. Maximum rotor temperature limited to 300C
during starting.
NOTE: There is no direct US equivalent to an Exe
motor.
Division II motor - Internal and external surfaces of the
motor must not exceed 200C or the gas ignition
temperature, whichever is less.
Non-Sparking – noted as (Exn)
Temperature Classification
Ignition temperature is the minimum temperature of a surface at which an explosive atmosphere ignites.
Flammable vapors and gases can e classified into temperature classes according to their ignition
temperature. The maximum temperature of a piece of equipment must always be lower than the ignition
temperature if the gas/air mixture or vapor/air mixture in which it is placed. Equipment shall be marked to
show the operating temperature or temperature class referenced to a +40°C ambient. The temperature
class (T-Code) is indicated on the manufacturer’s nameplate and is based on the table below.
Maximum Temperature
NEC
T-Codes
Degrees C
450
T1
300
T2
280
T2A
260
T2B
230
T2C
215
T2D
200
T3
180
T3A
165
T3B
160
T3C
135
T4
120
T4A
100
T5
85
T6
NOTE: Both IEC and NEC assume 40C ambient.
IEC
T-Codes
T1
T2
T3
T4
T5
T6
IC Code
Abbreviation for International Cooling designation system concerning methods of cooling. Refers to
standard IEC 34-6. Also see definition for Enclosure.
IEC
International Electrotechnical Commission (IEC) is an organization founded in 1906 for the purpose of
coordination and unification of National standards on electrotechnology. Over 40 countries worldwide
participate in IEC standards.
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ATEX / IEC Motor Terminology
IECEx
The objective of the IECEx scheme is to facilitate international trade in electrical equipment intended for
use in explosive atmospheres.
Increased Safety – Type of Protection “e”
A type of protection applied to electrical and under specified product arcs or sparks in normal service and
under specified abnormal conditions, in which additional measures are applied so as to give increased
security against the possibility of excessive temperatures and of occurring of arcs and sparks.
IP Code
IP Codes is an abbreviation for classification of degrees of protection provided by enclosures of rotating
machines. Also see definition for Enclosure.
Insulation
IEC standards define the maximum allowable temperature rise by class of insulation. See the table below
for the insulation class and respective rises in degree C:
Class of
Insulation
A
E
B
F
H
Rise by Resistance in C
NEMA @ 1.0 SF
60
80
105
125
IEC
60
75
80
100
125
NEMA @ 1.15 SF
70
90
115
-
NEMA allows additional 5C for non-ventilated and encapsulated motors (10C for class H non-ventilated)
where IEC has no such allowance.
NEMA ties rise to Service Factor and makes allowance for 1.15 SF. In the IEC world the term “Service
Factor” has no meaning. Everything in the IEC terminology is evaluated at nameplate KW.
kW Rating
IEC uses KW or kilowatts to denote power vs. NEMA using HP or horsepower. The IEC standard KW
rating and the approximate corresponding NEMA horsepower is provide for reference purposes only.
The formula is: KW = HP X .746
kW
HP
kW
HP
.25
1/3
18.5
25
.37
½
22
30
.55
¾
30
40
.75
1
37
50
1.1
1½
45
60
1.5
2
55
75
2.2
3
75
100
3
4
90
125
4
5
110
150
5.5
7.5
132
175
7.5
10
150
200
11
15
186
250
15
20
224
300
Lead Labels
A NEMA motor normally identifies the leads as T1, T2, T3 whereas IEC motors use U, V, W.
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ATEX / IEC Motor Terminology
Marking
All equipment and protective systems must be marked legibly and indelibly with the following minimum
information:
 Name and address of the manufacturer
 CE marking, if involved, the identification number or the notified body
 Designation of series or type
 Serial number, if any
 Year of construction
 The community mark
 The equipment group and the category
 For Group II, the letter “G” (concerning explosive atmospheres caused by gases, vapors or mists)
and the letter “D” (concerning explosive atmosphere cased by dust)
Metric Frame
The frame measurement is a decimal system covered under IEC specification 72. An IEC frame 112S or
112M or 112L denotes a 112 mm shaft height and is denoted on a dimensional drawing as “H.” The S, M
or L stands for Small, Medium or Long.
N
Is referred to as speed, revolutions per minute and is a standard marking on a nameplate.
NEMA
Abbreviation for National Electrical Manufacturers Association.
Non-explosive Atmosphere
An atmosphere with no explosive components.
Power Factor
On an IEC nameplate it is expressed as the Cosine (Cos ) which is a definition of Power Factor. Power
Factor is a measurement for the time phase difference between the voltage and current in an AC circuit. It
is represented by the cosine of the angle of this phase difference.
S Code
This code defines the motor duty cycle. Also see definition for Duty.
Temperature Class (gas atmospheres)
Electrical motors are classified into six classes according to the maximum surface temperatures.
Terminal Box
Power leads are run separately from the control leads therefore it is common to have all thermistors,
space heaters etc… in an auxiliary conduit box with it’s own terminal strip. Many times IEC motors supply
terminal connections via terminal blocks or strips. This is not required by the IEC specifications but is a
common industry standard. NOTE: When a specification refers to “leads are eft to dangle,” this means
the leads are not connected to a terminal block or strip. Most European inspectors consider the motor
incomplete if there are no terminal blocks in the conduit box.
V1 Mounting
Mounting arrangement with the motor flange at the drive end and no base. The shaft is in the vertical
plane with the drive end down.
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ATEX / IEC Motor Terminology
V3 Mounting
Mounting arrangement with the motor flange at the drive end and no base. The shaft is in the vertical
plane with the drive end up.
Voltage
Common Voltage Combinations
IEC @ 50HZ
NEMA @ 60HZ
190
230
190/380
230/460
380
460
400
575
415
-
Wye-Delta Starting
Wye-Delta is a connection that is used to reduce the inrush current and torque of a polyphase motor. In
the IEC world it is an industry practice that all motors 160 frames and larger come set up for Wye-Delta
connection. This is not required by IEC specifications, therefore it is common that 160 frame and up
conduit boxes will have two lead entry holes, one for the Wye connection cable and one for the Delta
connection where the actual reconnect is done back at the starter.
Zone Classification
The user of the hazardous duty equipment has the responsibility to classify the areas in which explosive
atmospheres may be present into zones and to ensure that the minimum organizational and technical
requirements of the directive are observed.
Zone 0
An area in which an explosive mixture of gases or vapors is continuously present or present for long
periods. Equivalent to the North American classification system Class I Division I (gases).
Zone 1
An area in which an explosive mixture is likely to occur in normal operation. Equivalent to the North
American classification system Class I Division 2 (gases).
Zone 2
An area in which an explosive mixture is not likely to occur in normal operation and if it occurs, it will exist
only for a short time. Equivalent to the North American classification system Class I Division 2 (gases).
Zone 20
An area in which an explosive mixture is continuously present or present for long periods. Equivalent to
the North American classification system Class II Division 1 (dusts).
Zone 21
An area in which an explosive mixture is likely to occur in normal operation. Equivalent to the North
American classification system Class II Division 1 (dusts).
Zone 22
An area in which an explosive mixture is not likely to occur in normal operation and if it occurs, it will exist
only for a short time. Equivalent to the North American classification system Class II Division 2 (dusts).
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