# Simple introduction inverter common problems

UpdateTime：2013-01-08Clicks：1184Word Size：T|T

1, What is the frequency converter?
Inverter is the use of power semiconductor devices the on-off function of the power frequency power conversion to another frequency power control device, can realize the ac asynchronous motor soft start and frequency control of motor speed, improve the operation accuracy, change the power factor, over current/over voltage/overload protection, and other functions.

2,What is the difference of 2, PWM and PAM?
PWM is English Pulse Width Modulation (Pulse Width Modulation) abbreviation, change the Pulse Width of Pulse train according to certain rule, and to regulate the output waveform of a way of Modulation.PAM is English Pulse Amplitude Modulation (Pulse Amplitude Modulation) abbreviation, is change the Pulse Amplitude Pulse train, according to certain rule to adjust the output value and waveform of a way of Modulation.

3, What's the difference between a voltage type and current type?
The main circuit of frequency converter in general can be divided into two categories: voltage type is the dc voltage source transformation for ac frequency converter, dc loop filter is capacitance; Current mode is the current source dc transform for ac frequency converter, the dc loop filter is the inductance.

4, why the inverter voltage and frequency is proportional to the change?
All the electromagnetic torque of the motor is the result of the interaction between electric current and magnetic flux and current are not allowed to exceed the rating, otherwise will cause the motor of fever. Therefore, if the flux decreases, and electromagnetic torque will be reduced, reducing load capacity. By E = 4.44 F * * K * N * Φ can be seen that the frequency control of motor speed, the magnetic circuit of the motor with frequency fX is within the scope of the considerable changes, it is very easy to make the magnetic circuit of the motor serious saturation, lead to serious distortion of waveform of exciting current to produce a high peak of peak current. Is proportional to the frequency and voltage, therefore, to change, namely the change frequency control inverter output voltage at the same time, to keep the flux of the motor must be to avoid weak magnetic and magnetic saturation phenomenon. This kind of control method used in fan and pump more energy-saving frequency converter.

5, when labor frequency power driven motor current to increase the voltage decline; For the inverter drive, if voltage is reduced when the frequency drops, so whether the current increase?
Frequency (low speed), if the output of the same power, the current is added, but in certain conditions, the torque current is almost the same.

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