The difference between ordinary motor and variable frequency motor measurement
1. The actual output waveform of the inverter is PWM wave. In addition to the fundamental wave, it also contains the carrier signal. The carrier signal frequency is much higher than the fundamental wave, and it is a square wave signal, which contains a large number of higher harmonics. For the test system, higher sampling frequency and bandwidth are required.
2. In the environment where the inverter is powered, various high-frequency interferences are everywhere, and electromagnetic interference is much stronger than the power frequency environment. This requires the test system to have stronger electromagnetic compatibility.
3. The crest factor of the PWM wave is generally high, and the ordinary instrument basically meets the requirements. For the frequency conversion test system, a higher measurement crest factor measurement capability is required.
4. The instrument used for frequency conversion test should have the ability to decompose its fundamental wave in various PWM waveforms. Strict measurement requires digital signal processing, that is, high-speed sampling to obtain the sample sequence, and then discrete sample of the sample sequence. The leaf transform obtains the amplitude and phase of the amplitude, phase and harmonics of the fundamental wave.
For the mainstream instruments of current frequency measurement, Hall sensor plus variable frequency power analyzer is a choice of many manufacturers, but the limitations of this method are constantly expanding, mainly because the interference problem in the transmission link is difficult to solve. This is a fatal injury to this type of measurement. The use of front-end digital power analyzers can solve this problem, which will become the main way of frequency conversion measurement.
The reason why the variable frequency motor saves energy is not that the loss of the inverter motor itself is low. On the contrary, under non-sinusoidal voltage and current, the higher harmonics will cause the copper loss, rotor copper loss, iron loss and additional loss of the motor to increase. The energy saving of variable frequency motor is to adapt to different use environments by constant speed regulation, so as to reduce the unnecessary loss. If it is operated in the power frequency environment at the same time, the difference between the variable frequency motor and the ordinary motor is not big, even the variable frequency motor. More energy-consuming, that is to say we can not blindly believe that the frequency conversion must be energy-saving.
The above is the difference between the variable frequency motor and the ordinary motor. The user can select the appropriate motor according to its characteristics.
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