Question 136Electricity/Electronics - QMED70% to pass
The illustrated motor fails to start and gives a loud hum when the start button is depressed, what should then be your first action? Illustration EL-0007
AI Explanation
The correct answer is B) push the stop button to de-energize the "M" coil.
When a motor fails to start and gives a loud hum, it indicates that the motor windings are energized but the rotor is not turning. This is likely due to a fault in the motor or the starting circuit. The best first action is to de-energize the motor by pushing the stop button, which will cut power to the "M" coil and the motor windings. This will prevent further damage to the motor and allow you to diagnose the issue safely.
The other options are incorrect because: A) disassembling the motor is not the first step and could further damage the equipment; C) resetting the thermal overload does not address the root cause of the issue; and D) holding the "M" contactor closed manually is unsafe and could lead to electrical shock hazards.
Related Questions
#134 The motor starts when the start button in the illustration is pushed, but stops when the button is released. What is most likely the trouble? Illustration EL-0007 #135 The motor fails to start on an attempted startup. With the start button depressed, a voltmeter reading between 1 and 5, as illustrated in figure "A", indicates line voltage available to the control circuit, what should be your next step in the troubleshooting process? Illustration EL-0007 #137 What can be the cause of excessive heat or burning contacts in an operating motor controller? #138 A capacitor is to be tested with a digital multimeter set up to measure ohms. If the meter is connected to a shorted capacitor, how would the meter display respond? #139 If a digital multimeter is set up as shown in figure "A" of the illustration to test a capacitor, what would the display read if the capacitor is shorted? Illustration EL-0213