motor nameplate information #2 – Mechanical input

Last time i already explain about Electrical input. This time i want explain about mechanical output electric motor such as horse power,RPM ( running per minute),torque and slip.

From this data we can calculate and design a suitable mechanical device for output load such as pump,propeller,compressor,cutting machine,blower and etc.

We also can determine a correct size for motor coupling,diameter of shaft,load pressure and type of material for our machine or equipment design.

I explain detail about mechanical output information normally we can found at electric motor name plate.

Mechanical Output

  • Horsepower

Shaft horsepower is a measure of the motor’s mechanical output rating, its ability to deliver the torque required for the load at rated speed. It is usually given as “HP” on the nameplate.
In general:

HP = (Torque) x (speed)/5,250
where: Torque is in lb-ft. Speed is in rpm

  • Full-load speed

The speed at which rated full-load torque is delivered at rated power output is full-load speed. It is generally given as RPM on the nameplate.This speed is sometimes called “slip” speed or actual rotor speed rather than synchronous speed.

  • Design

It defines the torque and current characteristics of the motor.The motor manufacturer may assign them a letter that is not a defined industry standard. It is important to check the design letter when replacing a motor in an existing application.For detail refer to NEMA MG 1 (1987), Section MG 1-1.16, defines “design,”


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