Heat Exchanger: A device which will transfer the heat from inside the motor to another medium, through a radiator type heat exchanger.

Hertz (HZ): One cycle per second (as in 60 Hz which is 60 cycles per second).

Holding Torque: Sometimes called static torque, holding torque specifies the maximum external torque that can be applied to a stopped, energized motor without causing the rotor to rotate. Generally used as a figure of merit when comparing motors.

Horsepower (HP): The measure of rate of work. One horsepower is equivalent to lifting 33,000 pounds to a height of one foot in one minute. The horsepower of a motor is expressed as a function of torque and speed. For motors the following approximate formula may be used: HP =T x RPM 5250 Where HP = horsepower, T = torque (in. lb. ft.), and RPM = revolutions per minute.

Horsepower: An index of the amount of work a machine or motor can perform. One horsepower is equal to 746 watts. Since power is equal to torque multiplied by speed, horsepower is a measure of a motor's torque and speed capability; e.g., a 1 HP motor will produce 36 lb-in. at 1,750 rpm. Formula: HP = Torque (lb-in.) x Speed (RPM)/63,025 or HP = Torque (lb-ft.) x Speed (RPM)/5,252 or HP = Volts x Amps x Efficiency/746

Hybrid Step Motor: A motor designed to move in discrete increments of steps. The motor has a permanent magnet rotor and a wound stator. Such motors are brushless. Phase currents are commutated as a function of time to produce motion.

Hysteresis Loss: The resistance offered by materials to becoming magnetized (magnetic orientation of molecular structure). This results in energy being expended and corresponding loss. Hysteresis loss in a magnetic circuit is the energy expended to magnetize and demagnetize the core.

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