Torque

Torque is the twisting force exerted by the shaft or a motor. Torque is measured in inch pounds, foot pounds, and on small motors, in terms of inch ounces.

Full Load Torque

Full load torque is the rated continuous torque that the motor can support without overheating within its time rating.

Peak Torque

Many types of loads such as reciprocating compressors have cycling torque where the amount of torque required varies depending on the position of the machine. The actual maximum torque requirement at any point is called the peak torque requirement. Peak torque are involved in things such as punch presses and other types of loads where an oscillating torque requirement occurs.

Pull Out Torque

Also known as breakdown torque, this is the maximum amount of torque that is available from the motor shaft when the motor is operating at full voltage and is running at full speed. The load is then increased until the maximum point is reached. Refer to Figure 11.3.

Pull Up Torque

The lowest point on the torque speed curve for a motor accelerating a load up to full speed is called pull up torque. Some motors are designed to not have a value of pull up torque because the lowest point may occur at the locked rotor point. In this case, pull up torque is the same as locked rotor torque.

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% OF SYNCHRONOUS SPEED

Figure 11.3 Typical speed—torque curve.

0 20 40 60 80 100

% OF SYNCHRONOUS SPEED

Figure 11.3 Typical speed—torque curve.

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