The motor type test bench adopts PLC industrial control technology and adopts a computer data acquisition and control system with upper and lower structure to measure the motor power, current, voltage, frequency, torque, speed, efficiency, power factor, and temperature rise. Next, the editor of the motor type test bench will introduce to you the voltage and current measurement methods
Traditional voltage and current measurements generally use methods such as mean detection, peak detection, and true effective value method. This article compares the applicability and advantages of various methods.
1, Mean wave detection
Using the average detection method to convert AC sine wave electricity into DC electricity proportional to its mean, the measurement circuit is simple, and the measurement results convert the waveform coefficients of the sine wave into effective values. The waveform factor of a sine wave is approximately 1.1107. The average detection method utilizes the waveform factor of sine waves, so it can only measure other waveforms that are the same as sine waves or waveform factors. The mean detection method is widely used in the AC-DC conversion circuit of AC voltage and current measurement circuits in multimeters. The AC-DC conversion circuit constructed using the mean detection method rectifies the AC signal by half wave or full wave rectification, and then uses the pulsating DC signal output from rectification to obtain a smoother DC signal using an integration circuit. The amplitude of the DC signal is the half wave rectification average or full wave rectification average of the measured signal. The AC-DC conversion circuit constructed using the half wave rectification average or full wave rectification average of the measured signal is then used to obtain a smoother DC signal.
2, Peak detection method
The peak detection method is used to convert the AC sine wave power of the motor type test bench into DC power. The peak value is proportional to the DC power, and the measurement circuit is simple. It is divided by the sine wave peak factor and the effective value of the measured power. The peak factor of a sine wave is about 1.414, and the peak detection method utilizes the peak factor of a sine wave, so it can only measure other sine waves or waveforms with the same peak factor as a sine wave. Peak detection method is one of the commonly used AC/DC conversion circuits. The AC-DC conversion circuit constructed using peak detection method rectifies the AC signal by half wave or full wave, and then uses a charging capacitor to make the pulsating DC signal output by rectification reach its peak value, thereby obtaining a smoother DC signal. The amplitude of the DC signal is the peak value of the AC signal, and the relationship between the peak value and the effective value of the measured signal is then utilized.
3, True effective value method
By using a true effective value conversion circuit to convert AC electricity into DC electricity proportional to its effective value, the DC electricity can directly reflect the effective value of the measured AC electricity. This method is suitable for measuring the effective value of AC electricity of any waveform and measuring DC electricity.