EETC Electrical Equipment & Maintenance 3

Question 1

When replacing a failed contactor, which specification is MOST critical to match for motor protection?

Accepted Answer

Continuous current rating and interrupting capacity

Answer

The continuous current rating must handle full-load amperes and the interrupting capacity must safely break fault currents without damage.

Question 2

In a variable frequency drive (VFD), what is the function of the DC bus capacitor bank?

Accepted Answer

Filter and smooth the rectified DC voltage for the inverter section

Answer

DC bus capacitors smooth the pulsating rectified voltage into steady DC, reducing ripple and providing energy storage for the inverter section.

Question 3

What does a high dielectric absorption ratio (DAR) value indicate about transformer oil?

Accepted Answer

Oil is in good condition with high dielectric strength

Answer

A high DAR (ratio of 60-second to 30-second insulation resistance) indicates clean, dry insulating oil with good dielectric properties.

Question 4

A power factor correction capacitor bank is found to have one failed (open) capacitor unit. What is the immediate effect on the bank?

Accepted Answer

Remaining units in that phase see increased voltage stress

Answer

With one capacitor open in a series-parallel bank, remaining parallel capacitors in that section carry the full voltage, increasing stress and risk of cascading failure.

Question 5

During preventive maintenance on switchgear, vacuum bottle integrity is verified by:

Accepted Answer

Applying a high-potential (hi-pot) test across open contacts

Answer

A high-potential test across the open vacuum interrupter verifies that the vacuum is intact and can withstand the required dielectric strength.

(EETC) Electrical Technician Certification Practice Test

(EETC) Electrical Technician Certification Practice Test

EETC Electrical Equipment & Maintenance 3