Glossary & Technical Reference

Force acting parallel to the motor shaft axis. The allowable value depends on the bearing system, speed, duty and mounting arrangement.

Voltage induced in a motor winding by rotor movement that opposes the applied voltage. In a permanent-magnet motor, its magnitude is commonly related to speed, winding design and drive requirements.

Angular or linear lost motion between mating transmission components before output movement begins.

The frequency range over which a control system can respond effectively. Higher bandwidth can improve dynamic response but depends on the complete mechanical and electrical system.

The controlled switching of current between motor windings to maintain torque-producing magnetic alignment.

Position-dependent torque in a permanent-magnet motor caused by interaction between the magnets and stator slots when no winding current is applied.

Torque that can be sustained under stated supply, cooling, ambient and duty conditions without exceeding the permitted thermal limit.

The internal direct-current supply within an electronic drive, typically produced by rectification or supplied directly from a DC source.

A deliberate reduction in permissible output because operating conditions differ from the declared rating conditions.

The relationship between operating time, load, speed and rest periods used to determine thermal and mechanical capability.

Useful mechanical output power divided by electrical input power, stated at a defined operating point and test condition.

The ability of equipment to operate correctly in its electromagnetic environment without creating unacceptable interference.

A feedback device providing incremental or absolute information about shaft position, speed or direction.

The relationship between input and output speed in a gearbox. The corresponding torque change must also account for gearbox efficiency and operating direction.

A magnetic sensing device commonly used to provide discrete rotor-position information for electronic commutation.

The maximum static torque a stepper motor can resist at zero speed under stated current and thermal conditions. It is not the same as available running torque or detent torque.

Resistance of a rotating mass to a change in speed. Reflected load inertia is central to acceleration, control response and motor sizing.

A thermal classification for an insulation system. It does not by itself define the permissible motor temperature rise or service life.

A classification describing enclosure protection against access, solid objects and water under specified test conditions.

Short-duration torque capability available within defined current, speed, thermal and mechanical limits.

The ratio of real power to apparent power in an AC system under stated operating conditions. It describes supply utilisation and is not the same as efficiency.

Useful output power relative to motor mass or package volume, meaningful only when rating and cooling conditions are also stated.

A switching method used by electronic drives to control effective motor voltage and current.

Force acting perpendicular to the motor shaft axis, often created by belts, gears or overhung loads.

The declared shaft speed at a specified operating point, supply and load condition.

Controlled deceleration in which mechanical energy is converted into electrical energy. The drive and supply determine whether that energy is returned, stored or dissipated.

A robust electromagnetic feedback device that provides angular rotor-position information, often for demanding environments.

The square root of the time-weighted mean of torque squared over a duty cycle. It is a useful thermal indicator where copper loss follows current squared, but it does not replace checks of speed-dependent cooling, peak limits or other losses.

A control method that estimates rotor position or speed from electrical behaviour rather than a shaft-mounted feedback device.

A multiplier describing permitted operation above a stated rating under defined conditions. Its meaning and allowable use depend on the applicable standard and manufacturer data.

Torque produced at zero shaft speed under stated voltage or current conditions. Unless specifically rated for continuous holding, stall operation is normally limited by winding and drive temperature.

A parameter describing how quickly a motor temperature approaches a new steady condition after a change in loss or cooling, based on a stated thermal model and reference point.

The relationship between motor torque and winding current under defined units and operating assumptions.

A plot showing available or required torque across the operating-speed range under stated supply, control, duty and thermal conditions.

Adjustment of control-loop parameters to achieve the required stability, response and disturbance rejection with the connected load.

An electronic drive that controls AC motor speed and torque by varying output frequency and voltage.