Torque To Spare
NEMA MG-1 defines various letters (A,B, C, D, E) which describe a motor's torque
characteristics, locked rotor current and to some extent efficiency.
Design A and B motors (1 to 500 HP) have the same torque requirements, but no limit is
imposed on A for locked rotor current. Design C motors (1 to 200 HP only; NEMA does not
address sizes greater than 200) have higher starting torque than A or B, but lower breakdown
torque.
Crushers and other equipment used in the aggregate and construction industries typically have
large inertia values. In order for the motor to get up to speed, it needs high locked rotor torque
to overcome the machine s momentum. It also needs high breakdown torque to handle the "shocks" when material is fed into the machine.
LINCOLN ADVANTAGE: Most Lincoln Crusher Duty motors have starting torques which surpass NEMA Design C requirements. All sizes have breakdown torques (BDT) which exceed NEMA Design B levels. The starting current of Lincoln motors are within the Design B maximum values so you don t have to worry about special control system requirements.
| HP |
Speed |
NEMA Design Letter(s) |
| Ultimate E1 |
Ultimate E2 |
| 100 |
1800 |
B & C |
B & C |
| 1200 |
B |
B & C |
| 125 to 200 |
1800 & 1200 |
B & C |
B & C |
| 250 to 400 |
1800 & 1200 |
B |
B |
