Question 306Electricity/Electronics - Assistant Engineer70% to pass
What is a useful instrument for checking 3 phase AC motor performance by measuring possible unbalanced currents?
AI Explanation
The correct answer is C) clamp-on ammeter.
A clamp-on ammeter is a useful instrument for checking 3-phase AC motor performance by measuring possible unbalanced currents. It can easily measure the current in each of the three phases, allowing the operator to identify any significant imbalance that could indicate a problem with the motor or its power supply. This is an important diagnostic tool for maintaining the proper operation of 3-phase AC motors.
The other options are not as well-suited for this task. A D'Arsonval iron-vane probe (A) is generally used for measuring voltage, not current. A hand or battery-operated megger (B) is primarily used for testing insulation resistance, not motor current. A vibrating-reed frequency meter (D) is designed to measure frequency, not current.
Related Questions
#304 You are reconnecting a three-phase induction motor to the supply line. To prevent possible damage to the load, due to the wrong direction of rotation, what should be done? #305 Using the temperature correction factor for the winding insulation temperature graph shown in the illustration, what would be the correction factor and the corrected temperature to 40 degrees C for a motor with an insulation resistance of 4 megohms measured at 50 degrees C? Illustration EL-0046 #307 Large machines undergoing a resistance insulation testing using a megohmmeter should be discharged to remove any accumulated electrostatic/capacitive charge stored. When should this discharge be performed? #308 When using the test set-up shown in figure "A" of the illustration, besides the motor windings and the motor feeder cable, what circuit components are actually being meggered? Illustration EL-0027 #309 When you are making a high potential test (megger) on the motor coils of repaired electrical machinery to ground. What would a low resistance reading indicate?