To what does the code letter on a motor nameplate referencia?
NEMA defines locked rotor kVA per horse power with a series of code letter (A to V). Generally, the farther the code letter is from A, the higher the inrush current per hp. A replacement motor with a higher code letter may require different upstream electrical equipment, such as a larger motor starter.
The KVA code makes it easy to determine the starting current of a motor from its code letter. The LRA is dependent on a mathematical relationship between the code letter value, the HP, the rated voltage of the motor, and its operating power factor. All these are available on the motor nameplate.
The KVA code is important when replacing a motor. If replaced with one of a higher code letter, other related upstream electrical equipment, such as the motor starter, may require a change as well.
| NEMA CODE LETTER | KVA/HP WITH LOCKED ROTOR | APPROX MID RANGE VALUE |
| A | 0-3.14 | 1.6 |
| B | 3.14-3.55 | 3.3 |
| C | 3.55-3.99 | 3.8 |
| D | 4.00-4.49 | 4.3 |
| E | 4.5-4.99 | 4.7 |
| F | 5.0-5.59 | 5.3 |
| G | 5.6-6.29 | 5.9 |
| H | 6.3-7.09 | 6.7 |
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