Design letter vs. code letter on motor namplate

[cccelcj]

Can anyone explain the difference between code letter and design letter date found on motor nameplates? It apperas though both are related to locked rotor current. What is the difference between the two?

 

[bjenks]

NEMA Code letter (as explain in next paragraph) should not be confused with the NEMA Design letter which refers to the motor's torque curve.

NEMA CODE LETTERS FOR LOCKED-ROTOR KVA: The letter designations for locked-rotor kVA per horsepower as measured at full voltage and rated frequency.

I am usually using the NEMA Code Letters to determine LRA.

 

[CJCPE]

The design letter designates the shape of the torque vs. speed curve. Design B is the "standard" or most common type with 2 to 3% slip at full load. Design D is a high slip motor with high starting torque. Locked rotor current is related to the design types. You should be able to find descriptions of all of the NEMA designs in NEMA MG1, condensed version is a free download at NEMA.org.

The locked rotor code letters designate specifie ranges of locked rotor KVA per horsepower. There is a table in MG1.

 

[jraef]

You use the DESIGN letter to select the proper motor for your task based upon the torque speed curve. You then use the CODE letter in determining the electrical capacity and protection of the circuit.

JRaef.com
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[petronila]

Hello cccelcj,

This WEB could help you:

http://www.egr.msu.edu/age/extension_outreach/technote103

regards

Petronila

 

[jraef]

It's a 404 link now!