Motor
IEC vs. NEMA
Date: 28 March 2003
What is IEC?
-
IEC (International Electrotechnical Commission) is a standard of recommended
electrical practices generated by signatory member nations. IEC provides an
‘umbrella’ for electrical standards under which countries form their own (local)
codes.
What is NEMA?
-
NEMA (National Electrical Manufacturers Association) provides standardization of
electrical equipments by defining product, process and procedure. NEMA standard for
motor provides information guide for general purpose industrial AC small and medium
squirrel-cage induction motors.
IEC vs. NEMA Enclosure Designations
IEC *
IP 23
IP 24
IP 54
IP 55
NEMA
Open Drip-Proof
WPII
Totally Enclosed (Fan or Water)
Totally Enclosed (Fan or Water, Additional
Protection)
* First Numeral: Protection against Airborne Particles
Second Numeral: Protection against Ingress of Water
IEC vs. NEMA Cooling Designations
IEC
IC 01
IC 411
IC 611
IC 616
IC 81W
NEMA
ODP or WPII
(Cooled via free exchange of air)
TEFC (Fin-cooled)
TEAAC or CACA (Tube-Cooled, Shaft Fan)
TEFC (Tube-Cooled, External Fan)
TEWAC
Motor
IEC vs. NEMA
Date: 28 March 2003
IEC Tolerances
Tolerance
Summation of Losses
≤ 50 KW
> 50 KW
Total Losses (>50 KW)
Power Factor
Slip
Locked-Rotor Current
Locked-Rotor Torque
Maximum Torque
-15% of (1-ε )
-10% of (1-ε )
+10% of Total Losses
-1/6 of (1-Cos θ)
± 20%
+ 20%
-15%, +25%
-10%
IEC vs. NEMA Performance Considerations
Characteristics
Power Supply
Max. Voltage Variation
Max. Frequency Variation
Max. Wave Shape Deviation
Max. Negative Sequence Voltage
Max. Zero Sequence Voltage
Standard Service Conditions
Cooling Air
Cooling Water
Altitude
Stray-Load Loss
IEC
NEMA
±5%
± 10 %
±2%
5%
2%
2%
±5%
5%
1%
--
≤ 400 C
≤ 250 C
1000 Meters
0.5 % of Input
≤ 400 C
≤ 300 C
1000 Meters
1.2% of Output < 2500 HP
0.9% of Output ≥ 2500 HP
IEC vs. NEMA Hazardous Areas
IEC
ZONE 0
ZONE 1
ZONE 2
( * ) No direct comparison
NEMA
(*)
DIV. 1
DIV. 2
Motor
IEC vs. NEMA
Date: 28 March 2003
Classification of Gases and Vapors According to Temperature Code and
Transmission of Ignition:
Ignition
Class
IIA
T-1
T-2
Temperature Class
T-3
Amylactrate-nbutane
N-butyl-alcohol
Cyclohexanon
1,2
dichlorethane
Acetic anhydride
Napthas
Petrol Fuels
for engines
Jet Engine
fuels
Fuel oils
N-hexane
IIB
Acetone Ethane
Ethylchloride
Ammonia
Benzene
Acetic Acid
Carbon
Monoide
Methane
Methanol
Town Gas
Ethanol ethylene
Hydrogen
sulfide
IIC
Hydrogen
Acetylene
T-4
Maximum Surface
Temperature, 0C
450
300
200
135
100
85
Hazardous Areas to IEC 79-10
Zone 2, Area unlikely in normal operation, may happen for short time only.
Designation E xnAII
Zone 0, or Zone 1, Area likely in normal operation.
Zone 1, designation E xde IIC
IEC Types of Protection
EE x (n) II T3: ‘NON-SPARKING’ - ZONE 2
EE x (en) II T3: ‘INCREASED SAFETY’ – ZONE 1 OR 2
EE x (de) IIC T3 or T4: ‘FLAMEPROOF’ – ZONE 1
EE x (pe) II T3: ‘ PRESSURIZED’ – ZONE 1
T-6
Acetaldehyde
Diethylether
IEC Temperature Classes
Temperature
Class
T1
T2
T3
T4
T5
T6
T-5
Carbon
Sulfide