430.6(A)(1)

[charlie b]

For motors built for low speed or high torque, we use the nameplate current instead of the tables. But in general, how would I know if a given motor was built for low speed or high torque? More specifically, must I treat every elevator motor as though it were built for low speed or high torque?

 

[tom baker]

The motor design determines the speed and torque, by that I mean NEMA has motor designations, Design B is the most common, others are design C and D, used for elevators and punch presses. NEMA should have a document on motor design types

 

[petersonra]

The motor design determines the speed and torque, by that I mean NEMA has motor designations, Design B is the most common, others are design C and D, used for elevators and punch presses. NEMA should have a document on motor design types

I wish the NFPA would include more informational notes indicating just what they mean by some of these terms they have not bothered to otherwise define. There is a lot of stuff that they just sort of assume someone will somehow know what they mean.

 

[augie47]

It might be worth noting that 430.5 refers you to Art 620 for elevator motors where 620.13 sates for elevator motors nameplate values shall be used.

 

[charlie b]

Gus, both of those articles address the conductors. My issue concerns the amount of load I need to include, when calculating the minimum rating of the power source.

 

[Smart $]

Gus, both of those articles address the conductors. My issue concerns the amount of load I need to include, when calculating the minimum rating of the power source.

430.6(A)(1) is specific about motors built for low speed as it states less than 1200RPM.

Design C & D NEMA-rated motors are designed for high-torque applications.

Suggest you get a copy of ANSI/NEMA MG 1.

Here is a passage from PART 20 LARGE MACHINES - INDUCTION MACHINES...

20.10 TORQUE

20.10.1 Standard Torque
The torques, with rated voltage and frequency applied, shall be not less than the following:

Torques	Percent of Rated Full-Load Torque
Locked-rotor*	60
Pull-up*	60
Breakdown*	175
Pushover**	175

*Applies to squirrel-cage induction motors or induction generators when specified for self-starting
**Applies to squirrel-cage induction generators
In addition, the developed torque at any speed up to that at which breakdown occurs, with starting
conditions as specified in 20.14.2, shall be higher than the torque obtained from a curve that varies as the square of the speed and is equal to 100 percent of rated full-load torque at rated speed by at least 10 percent of the rated full-load torque.

20.10.2 High Torque
When specified, the torques with rated voltage and frequency applied, shall not be less than the following:

Torques	Percent of Rated Full-Load Torque
Locked-rotor	200
Pull-up	150
Breakdown	190

In addition, the developed torque at any speed up to that at which breakdown occurs, with starting
conditions as specified in 20.14.2, shall be higher than the torque obtained from a curve that has a constant 100 percent of rated full-load torque from zero speed to rated speed, by at least 10 percent of
the rated full-load torque.