CEA CEA Motor Controls and Control Circuits Questions and Answers 2

Question 1

In a forward/reverse motor control circuit, what must be used to prevent both forward and reverse contactors from energizing simultaneously?

Accepted Answer

Mechanical and/or electrical interlocking

Answer

Interlocking (both mechanical between the contactor frames and electrical using normally closed auxiliary contacts) prevents both contactors from closing at the same time, which would cause a short circuit.

Question 2

What does a time-delay relay (TDR) set for 'on-delay' do?

Accepted Answer

It waits a preset time after being energized before changing contact states

Answer

An on-delay TDR energizes its coil immediately but waits the set time interval before its timed contacts change state.

Question 3

Which device in a motor control circuit is used to stop the motor automatically when a conveyor reaches a certain position?

Accepted Answer

Limit switch

Answer

A limit switch is a mechanical position sensor wired into the control circuit that automatically opens or closes contacts based on physical position.

Question 4

What is the typical control circuit voltage supplied by a control transformer in a magnetic starter panel?

Accepted Answer

120V

Answer

Most industrial motor control circuits use a control transformer to step the line voltage down to 120V for safer and more standardized control wiring.

Question 5

A two-wire control circuit uses which type of pilot device?

Accepted Answer

Maintained-contact device such as a toggle switch or thermostat

Answer

Two-wire control uses a maintained-contact device that holds the circuit open or closed without operator presence, providing low-voltage release and automatic restart.

(CEA) Certified Electrical Apprentice Practice Test

(CEA) Certified Electrical Apprentice Practice Test

CEA CEA Motor Controls and Control Circuits Questions and Answers 2