ITMC Electrical & Electronic Systems 2

Question 1

A three-phase motor draws 18A per phase at 480V. What is the approximate total power consumption?

Accepted Answer

14,968 W

Answer

Three-phase power = √3 × V × I = 1.732 × 480 × 18 ≈ 14,968 W.

Question 2

Which type of capacitor is commonly used for power factor correction in industrial motor circuits?

Accepted Answer

Run capacitor (oil-filled)

Answer

Oil-filled run capacitors are designed for continuous AC duty and are the standard choice for industrial power factor correction.

Question 3

When troubleshooting a PLC input module, the indicator LED is ON but the program logic shows the input as OFF. The most likely cause is:

Accepted Answer

Failed input module optocoupler

Answer

If the LED lights (indicating voltage at the terminal) but the PLC reads OFF, the optocoupler inside the input module has failed to pass the signal.

Question 4

An insulation resistance test on a 480V motor winding reads 0.8 MΩ. What action should be taken?

Accepted Answer

Motor should be removed from service for rewinding or drying

Answer

IEEE 43 recommends a minimum of 1 MΩ for motors operating below 1 kV; 0.8 MΩ falls below this threshold and warrants removal from service.

Question 5

Which wiring method provides the best protection against electromagnetic interference (EMI) in a signal cable?

Accepted Answer

Twisted pair with overall shield grounded at one end

Answer

Twisted pair cancels magnetically induced noise while a shield grounded at one end prevents ground loops and blocks electric field interference.

(ITMC) Industrial Technology Maintenance Certification Practice Test