User Guide

A motor nameplate is the ID card of a motor. It displays several information.

These informations are useful for the motor selection itself, useful for the Clean Power VFD selection, and they are used to set the Clean Power VFD parameters.

Usually given as hp or kW, this is a measure of the motor's mechanical power.

This designation specifies the length of time that the motor can carry its nameplate rating safely.

Usually this is “continuous” (Cont), which NEMA defines as indefinitely.

The duty for motors used intermittently (e.g., on cranes, hoists and valve actuators) is usually expressed in minutes.

This is the maximum allowable temperature of the surrounding air to ensure that the motor's operating temperature won't exceed the insulation system limit.

This indicates the motor winding's thermal endurance using industry standard letter designations such as A, B, F or H.

The pole count of a motor is the number of magnetic poles, north and south, on the rotor. There is always the same number of north and south poles on the rotor. For example, in a 12 pole motor, there are 6 north poles and 6 south poles. This motor would also be considered a 6 pole-pair motor.

The synchronous speed of the motor depends on the number of poles (2p) of the motor and on the line frequency (f) in Hertz (Hz).

AC Motor Speed Formula: Synchronous Speed (RPM) =120 x Frequency / Number of Poles

For example, the speed of a 4-Pole Motor operating at 60 Hz would be:

120 x 60 / 4 = 7200 / 4 = 1800 RPM

This is the speed at which rated horsepower output is delivered to the load (full-load speed).

This will be less than synchronous rpm, the speed of the stator's revolving magnetic field. The difference between the two is the “slip speed” or “slip rpm.”

Rated frequency of the AC power to be applied to the motor. The standard frequency is 60 Hz in North America and usually 50 Hz elsewhere.

Single or three phase of the AC power lines supplying the motor.

Rated load current in amps, at nameplate horsepower (hp) with nameplate voltage and frequency.

Rated voltage of the AC power to be applied to the motor.

NEMA MG 1defines locked rotor kVA per hp with aseries of code letters (A to V). Generally,the farther the code letter is from A, the higher the inrush current per hp.

NEMA MG 1defines four motor designs (A, B, C and D) in terms of torque and current characteristics.

Efficiency is defined as output power divided by input power,expressed as a percentage:

(Output/Input) x 100

At nameplate voltage and frequency, the allowable overload for a motor with a nameplate service factor equals the rated load multiplied by that service factor.

The service factor is only required on a nameplate if it is higher than 1.0.

Power factor is the ratio of active power (watts) to apparent power (volt-amperes) for the motor at full load.