Protective relays and monitoring relays detect or monitor for abnormal power system conditions.

Circuit breakers are mechanical switching devices capable of breaking currents under specified abnormal circuit conditions.

Overload relays prevent an electric motor from drawing too much current and overheating; includes thermal and solid state overload types

Power supplies are devices that produce AC or DC power.  This grouping includes current sources, DC power supplies, AC-DC adapters, DC-DC converters, AC power sources, and DC-AC inverters.

AC power sources provide alternating power and typically have adjustable output values for the testing of component response at various voltage, current and frequency levels.

DC power supplies accept an input power and output the desired form of DC power. Common types of DC power supplies include linear power supplies, switching power supplies, DC-DC converters, and silicon controlled rectifier (SCR) type power supplies.

DC motors are most commonly used in variable speed and torque applications. They include brushless and gear motors, as well as servomotors

Motor controllers receive supply voltages and provide signals to motor drives that are interfaced to motors. They include a power supply, amplifier, user interface, and position control circuitry

AC motors include single, multiphase, universal, induction, synchronous, and gear motors. They also include servomotors.  

Motor and generator winding services suppliers specialize in producing custom motors, generators and custom windings per customer specifications, as well as companies that specialize in motor repair and refurbishing. 

DC servomotors are generally small and powerful for their size, and easy to control. Common types of DC servomotors include brushless or gear motors

Motor starters and contactors are motor-starting devices. They combine a contactor with overload protection and are designed for starting AC or DC motors

Stepper motors use a magnetic field to move a rotor in small angular steps or fractions of steps. They provide precise positioning and ease of use, especially in low acceleration or static load applications

Gearmotors consist of an AC or DC motor with an integral gearbox or gear head that steps delivered speed up or down

Motor contactors are relays with large current capacity for connecting and disconnecting a motor from the power supply. Typically, motor contractors are multi-pole for control of all current carrying conductors