Question

Which of the following systems would be most likely to produce a power waveform that would require a true rms meter to accurately measure? select one:

a. a three-phase motor controlled by a variable-frequency drive
b. an electric strip heater controlled by a contactor
c. A shaded pole motor controlled by a relay
d. An incandescent light controlled by a toggle switch

Answer 1

A three-phase motor controlled by a variable-frequency drive most likely requires a true RMS meter for accurate measurement due to the complex waveforms produced by the drive.

Step-by-step explanation:

The system most likely to produce a power waveform that would require a true RMS meter to accurately measure is a three-phase motor controlled by a variable-frequency drive. Such a system can introduce non-sinusoidal waveforms due to the variable-frequency drive, which modulates the frequency and voltage to control the speed of the motor. Unlike simple resistive loads such as electric strip heaters or incandescent lights, which typically result in sinusoidal waveforms under AC power, the outputs from variable-frequency drives can be complex, and for accurate readings of power or current, a true RMS meter is needed to account for these irregular waveforms.