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These 10 free C-202 questions are organized by exam domain, so you can see how each part of the Electric Motor Control Systems 1 blueprint is tested. Reveal the answer and explanation under each question.
During a rated-load acceptance check, a four-pole, 60 Hz induction motor turns at its nameplate speed of 1,750 rpm. Voltage, phase currents, temperature, and vibration meet the specified limits. A trainee wants to reject the motor because its rotating magnetic field turns at 1,800 rpm. How should the speed result be assessed?
Correct answer: A - Accept it; the difference is normal slip while an induction motor produces torque.
A reversing starter uses forward contactor F and reverse contactor R. Each coil has a normally open direction button in parallel with its own normally open holding contact. Outside those parallel branches, each coil is in series with the opposite contactor's normally closed auxiliary. STOP and overload contacts are closed, and all components are healthy. The direction buttons have no normally closed contacts. With F already held in, the operator presses REVERSE without pressing STOP. What are the resulting coil states?
Correct answer: D - F energized; R deenergized.
A conventional control relay with a 120 V AC coil fails to pull in. A qualified electrician's operating test records 120 V AC directly across the coil terminals during the command. After all sources are isolated and verified deenergized, one coil lead is disconnected. A verified ohmmeter, on a range suitable for the specified coil resistance, reads OL across the coil. Which defect best fits both findings?
Correct answer: A - An open circuit within the relay coil.
A compressor must start unloaded for three seconds, then load while its motor continues running. Its unloader valve opens when the solenoid is energized and closes when the solenoid is deenergized. A timer's trigger turns ON with motor contactor M and stays ON throughout the run. An M normally open auxiliary is already in series with the solenoid. Which timer contact should also be wired in series with the solenoid?
Correct answer: D - An on-delay normally closed contact that opens after three seconds.
After a second pushbutton station is added to a three-wire motor circuit, its START works but its STOP cannot stop the motor once contactor M is sealed in. The drawing shows the new normally closed STOP only in series with the new START branch; M's holding branch bypasses it. How should the circuit be corrected so either station can stop the motor, even while a START is held?
Correct answer: C - Wire both STOP contacts in series ahead of all START and holding branches.
A pressure-building pump's switch closes at 40 psi on falling pressure and opens at 60 psi on rising pressure. The pump reaches 60 psi and stops. Later, pressure falls to 50 psi, but the pump remains off. Power is available and no protective device has tripped. An operator reports a suspected starter fault. Which assessment fits the observations?
Correct answer: B - The operation is normal; the pressure contact should remain open until pressure falls to 40 psi.
A reversing starter is being replaced. Its 480 V motor disconnect is locked open, and the motor power conductors have been verified deenergized. As a coworker prepares to loosen a control terminal, a qualified electrician notices that a separate, unisolated panel supplies the starter's 120 V control circuit. What takes priority?
Correct answer: B - Prevent contact; isolate, lock out, and verify the separate control supply is deenergized.
An internally wye-connected motor on a solidly grounded three-phase supply was running normally before isolation for inspection. Its equipment-grounding conductor is found disconnected from the frame, and no other effective bonding path exists. Which function has been lost despite the motor's ability to run?
Correct answer: B - The fault-current path from the frame back to the source through protective bonding.
An isolated 230/460 V motor is identified by its connection diagram as a standard nine-lead wye design. For operation on 460 V, L1 is assigned to T1, L2 to T2, and L3 to T3. Select the arrangement that completes the high-voltage connection.
Correct answer: C - Make three separate insulated pairs: T4-T7, T5-T8, and T6-T9.
A reversing starter has two identical coils, each requiring 180 VA at pickup and 18 VA when held. Interlocking prevents any overlap between coils, including during transitions. Indicators add 6 VA throughout pickup and running; there are no other loads. All four control transformers have the correct voltage and frequency ratings. Their listed pickup capacities maintain the required secondary voltage for these loads. Which is the smallest listed transformer that meets both load requirements?
Correct answer: D - 50 VA continuous capacity; 200 VA pickup capacity.
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