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ELECTRIC MOTOR WATTAGE GUIDE

Electrical motors present special electrical startup considerations. They can require up to three times their rated running wattage to start. Motor nameplates generally will show starting watts, some as high as nine times the running wattage. Check the nameplate to be sure. Be certain to use the starting watts when figuring the correct electrical load requirements.  If you don't have enough power to start you won't have enough to run.

Motor load requirements are listed below:

Motor Rating HP

Approximate Running Watts

Universal Motors Small Appliance

Reduction Induction Motors

Capacitor Motors

1/8

275

400

600

850

1/4

400

500

850

1050

1/3

450

600

975

1350

1/2

600

750

1300

1800

3/4

850

1000

1900

2600

1

1000

1250

2300

3000

1-1/2

1600

1750

3200

4200

2

2000

2350

3900

5100

3**

3000

3550

5200

6800

** Motors of higher HP are not generally used.

WATER WELL PUMP kW / kVA REQUIREMENTS

Pump Rating

Externally Regulated Generator

Internally Regulated Generator

 HP

Min. kW

Min. kVA

Min. kW

Min. kVA

1/3

1.5

1.9

1.2

1.5

1/2

2.0

2.5

1.5

1.9

3/4

3.0

3.8

2.0

2.5

1

4.0

5.0

2.5

3.125

1-1/2

5.0

6.25

3.0

3.8

2

7.5

9.4

4.0

5.0

3

10.0

12.5

5.0

6.25

5

15.0

18.75

7.5

9.4

7 1/2

20.0

25.0

10.5

12.5

10

30.0

37.5

15.0

18.8

NOTES: To avoid damage to your motor or pump, it is recommended that the generator be started and permitted to come up to voltage before the pump or motor is turned on.

  • A majority of industrial generators are externally regulated. Generators must be sized to deliver at least 65% of the rated voltage during motor starting to ensure adequate motor starting torque.
  • Industrial generators typically produce 300+ percent of rated capacity for 15-20 seconds during electrical surges.
  • To convert KW into watts multiply KW (x) 1000

NEMA CODES FOR STARTING KVA/hp THREE PHASE MOTORS

CODE
STARTING KVA / HP
TYPICAL SIZE RANGE
CODE
STARTING KVA / HP
TYPICAL RANGE
A
0 - 3.15
--
L
9.0 -10.0
1 HP
B
3.15 - 3.55
--
M
10.0 - 11.2
Less than 1 HP
C
3.55 - 4.0
--
N
11.2 - 12.5
--
D
4.0 - 4.5
--
P
12.5 - 14.0
--
E
4.5 - 5.0
--
R
14.0 - 16.0
--
F
5.0 -5.6
15 HP and up
S
16.0 - 18.0
--
G
5.6 - 6.3
10 HP
T
18.0 - 20.0
--
H
6.3 - 7.1
7.5 and 5 HP
U
20.0 - 22.4
--
J
7.1 - 8.0
3 HP
V
22.4 and up
--
K
8.0 - 9.0
2 and 1-1/2
 
 
 

 

 

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