What does a motor control center primarily contain?

A motor control center (MCC) primarily contains motor control units, which are essential for controlling the operation of electric motors in an efficient and organized manner. These units include various components such as motor starters, overload relays, and circuit breakers. The main purpose of an MCC is to house the equipment that helps regulate the starting, stopping, and protection of electric motors, thereby facilitating smooth operation in industrial and commercial applications.

Motor control centers provide a centralized location for managing multiple motors, which helps streamline maintenance and improve the monitoring of motor performance. By integrating multiple control units within one enclosure, MCCs enhance safety and efficiency, reduce installation and wiring costs, and facilitate easier troubleshooting and upgrades.

The other components mentioned in the choices serve different functions. Lighting units are not involved in motor control, power supply units provide electrical power rather than controlling motors, and transformers are used for voltage conversion in electrical systems but do not specifically relate to controlling motors' operation.