Electric Motor Generator Terminology

PMSM motor: A Brushless AC electric motor, similar to a brushless DC electric motor, whereby the magnetic field of the rotor is supplied by the permanent magnets rather than by electromagnets. However, the stator windings of brushless AC motors are sinusoidally distributed windings, while those of a brushless DC motor are salient field coils.

 

Direct drive: Drives that transmit power to the application directly without gears or other means of power transmission.

 

Efficiency (motor): the ratio of output to input (effectiveness of energy conversion).

 

Efficiency (system): the overall efficiency of the motor, controls, electric cables, drive train and driven equipment. This is determined by multiplying the individual component efficiencies together.

 

Power density: the power to weight ratio of a motor.

 

Torque constant: The rate at which torque increases with respect to current.

 

Back EMF (BEMF): the voltage generated when a permanent magnet motor is rotated. This is proportional to motor speed and is present whenever the rotor turns.

 

Neodymium magnet: A type of permanent magnet with Neodymium in the material structure (NdB Fe).

 

Samarium Magnet: A type of permanent magnet with Samarium Cobalt (SmCo) in the material structure.

 

Curie temperature: A characteristic property of a ferromagnetic material, often used as a reference point for assessing magnet capabilities.

 

Demagnetizing current:  The current at which the motor magnets will start to demagnetize.

 

Core losses: Losses in the core material hysteresis and eddy current losses. A core is the magnetic steel around which the windings of a motor are built.

 

Eddy current: Localized circulating currents induced in any material by alternating magnetic flux, causing losses and heating.

 

Flux density: The density of the magnetic field at any point in space.

 

Magnetic flux: A measure of quantity of magnetism, taking into account the strength and the extent of a magnetic field.

 

Saliency: the variation of the inductance at the motor terminal according to the rotor position. Also referred to as inductance saliency or magnetic saliency.

 

Permeability: A measure of how easily a magnetic field flows through a material.

 

Saturation: non-linear property whereby it becomes increasingly difficult to force additional magnetic flux through a material.

 

Resolver: an electromagnetic feedback device which converts angular shaft position into analog signals.