EETC Motor Controls 3

Question 1

A star-delta (wye-delta) starter is used primarily to:

Accepted Answer

Reduce starting current by initially connecting windings in wye

Answer

In star-delta starting, windings are first connected in wye (reducing voltage by 1/√3), then switched to delta for full-speed operation.

Question 2

What is 'plugging' in motor control?

Accepted Answer

Applying reverse phase voltage to quickly stop or reverse a running motor

Answer

Plugging applies reverse-phase power to a running motor to produce rapid braking, creating high braking torque.

Question 3

In a motor control ladder diagram, what does an X inside a circle symbol typically represent?

Accepted Answer

A pilot light

Answer

A circle with an X (or letter) inside typically represents a pilot light or indicator lamp in ladder logic diagrams.

Question 4

What is the primary purpose of a time-delay relay (TDR) in a reduced-voltage starter?

Accepted Answer

To allow the motor to accelerate before switching to full voltage

Answer

The TDR provides a timed delay so the motor can accelerate to near full speed before the circuit transitions from reduced to full voltage.

Question 5

Which enclosure type is rated for outdoor use and protection against rain, sleet, and snow according to NEMA standards?

Accepted Answer

NEMA 4

Answer

NEMA 4 enclosures are weatherproof and protect against rain, sleet, snow, windblown dust, and hose-directed water.

(EETC) Electrical Technician Certification Practice Test