Free C-303 Practice Questions

Question 1

A three-phase induction motor continues rotating but becomes abnormally hot. Before it is safely stopped and isolated, a qualified technician measures each supply conductor individually with a verified clamp meter. The steady readings are 0 A, 14 A, and 14 A. Which investigation should take priority?

Accepted Answer

Trace the missing phase through the supply and motor connections.

Answer

Check the motor's cooling passages for an airflow obstruction.

Answer

Check for deteriorated insulation between the windings and frame.

Answer

Check whether the driven equipment is imposing an excessive shaft load.

Question 2

Both windings carry current as a capacitor-start, induction-run pump motor accelerates normally in a guarded test. At running speed, the starting contact opens and auxiliary-winding current falls to zero. The main winding continues carrying normal running current. How should the technician assess the starting circuit?

Accepted Answer

Normal cutout leaves the main winding carrying running current.

Answer

The auxiliary circuit should remain energized; inspect its running-current path.

Answer

An open auxiliary winding is established; arrange a winding replacement.

Answer

A failed start capacitor is established; replace it before further checks.

Question 3

Two DC motors are isolated after field-circuit faults. Motor A has an open field winding in series with its armature. Motor B has an open shunt-field branch, and its parallel armature branch would remain energized when power is restored. Which pairing correctly predicts the consequences of restoring normal power before repair?

Accepted Answer

A loses armature current; B can overspeed under a light load.

Answer

A can overspeed under a light load; B loses armature current.

Answer

A loses armature current; B also loses armature current.

Answer

A can overspeed under a light load; B can also overspeed.

Question 4

Megohmmeter test record for a 460 V motor circuit: connected circuit, failed; motor alone, 200 MΩ; cable and terminations, 0.8 MΩ. The sections were safely isolated and discharged, with the cable disconnected at both ends. The procedure requires 500 V DC for 60 seconds and at least 5 MΩ for each section. All readings were taken under those conditions. What action does this record support?

Accepted Answer

Investigate and correct the cable or its terminations before repeating the required tests.

Answer

Send the motor for rewinding because the original connected-circuit test failed.

Answer

Replace the cable without inspecting its terminations; the reading proves damage within the cable insulation.

Answer

Repeat the cable test at 250 V DC and accept it if that reading exceeds 5 MΩ.

Question 5

A qualified technician locks out a 480 V motor and follows a procedure requiring the voltage tester to be proved immediately before and after the absence-of-voltage check. The tester works on the proving unit before the check and indicates zero at every required motor test point. On the final proving check, it fails to respond. What do these results establish?

Accepted Answer

Absence of voltage has not been established; repeat the procedure with a functioning tester.

Answer

The motor was deenergized when tested; only subsequent readings are uncertain.

Answer

The motor was deenergized because the locked disconnect supports the zero indications.

Answer

The motor circuit is energized; the final proving failure confirms that the isolation failed.

Question 6

Tightening the fourth mounting bolt shifts a motor's shaft out of alignment with its pump. During the isolated inspection, three motor feet rest firmly on the base, while a visible gap lies beneath the fourth. Tightening its bolt pulls that foot down. Which correction should come before final alignment?

Accepted Answer

Restore firm support beneath the foot before realigning the shafts.

Answer

Fit a more flexible coupling to absorb the movement caused by tightening the foot.

Answer

Replace the motor bearings because the alignment changes when the frame is restrained.

Answer

Offset the motor in the opposite direction before tightening the same unsupported foot.

Question 7

During a guarded motor acceptance test, measured real electrical input is 8.0 kW, efficiency at that operating point is 90%, and shaft speed is 1,750 rpm. The procedure requires at least 42 N·m at this test point. Use torque (N·m) = 9550 × shaft power (kW) ÷ speed (rpm). Which result should be recorded?

Accepted Answer

39.3 N·m; the measured test point falls below the torque requirement.

Answer

43.7 N·m; the measured test point meets the torque requirement.

Answer

35.4 N·m; the measured test point falls below the torque requirement.

Answer

48.5 N·m; the measured test point meets the torque requirement.

Question 8

A cumulative-compound DC motor is taken out of service after a reconnection test. It still turns in its original direction, but adding load now makes its speed rise abnormally. Armature supply voltage and shunt-field current stayed at their normal values. Which reconnection error best fits this change?

Accepted Answer

The series field was reversed relative to the unchanged shunt field.

Answer

The armature and both field connections were all reversed together.

Answer

The armature connections were reversed while both fields kept their polarity.

Answer

The shunt-field circuit was left open while the armature stayed connected.

Question 9

Since being moved from a 460 V supply to a balanced 230 V supply, a nine-lead 230/460 V series/parallel induction motor cannot accelerate its usual load. Supply frequency remains at the motor's rating. Isolated inspection finds the leads still arranged according to the 460 V connection diagram. Which condition best explains the reduced starting torque?

Accepted Answer

The coil sections remain in series and receive insufficient voltage.

Answer

The coil sections are paralleled and receive excessive voltage.

Answer

The coil sections remain in series, exposing each to excessive voltage.

Answer

The coil sections are paralleled and receive insufficient voltage.

Question 10

On a digital multimeter's resistance function, the reading rises to OL while testing the isolated, discharged run capacitor from a permanent split capacitor (PSC) blower motor with unreliable starting. The capacitor is disconnected from all parallel paths. A separate capacitance test places it within its marked tolerance. Which conclusion is supported?

Accepted Answer

The charging response can be normal; continue isolating the starting fault.

Answer

The final OL reading confirms an open capacitor that must be replaced.

Answer

The capacitance reading proves correct operation at full service voltage.

Answer

The rising resistance confirms dielectric breakdown under operating load.

Free C-303 Practice Questions

Domain 1: adhering to troubleshooting safety rules

Question 1

Domain 3: component testing

Question 2

Domain 4: using digital multimeters, clamp-on ammeters, and megohmmeter

Question 3

Domain 5: series/compound/shunt DC motors

Question 4

Question 5

Domain 6: dual voltage/wye/delta 3-phase AC motors

Question 6

Question 7

Domain 7: capacitor start/permanent/start-run/split phase single-phase AC motors

Question 8

Question 9

Domain 8: measuring motor speed/torque/power

Question 10

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