Frequency Converter

1, what is the frequency converter?

Inverter is to use the power of semiconductor devices to break a role will work frequency power transformation for another frequency power control device, can realize for ac asynchronous motor soft starter, frequency control of motor speed, improve operation precision, change the power factor, flow/pressure/overload protection etc. Function. Domestic technology is leading brands are the English has HuiChuan, three leaps, crystal, violet, electrical technology Co., LTD, Renault's, the red (former yantai HuiFeng), blue ocean China went up.

2, PWM and PAM what is the difference?

PWM is pulse width modulation abbreviations, according to certain rules change pulse list of the pulse width to adjust output waveform and a tone contours way.

PAM is Amplitude Modulation (English points Pulse Amplitude Modulation) abbreviations, is by a certain rule change Pulse list of Pulse Amplitude, to adjust the magnitude and the output waveform a Modulation mode. 3, the voltage type and the current model, is there any difference?

A frequency converter to the main circuit substantially can be divided into two classes: the voltage type is the dc voltage source will transform into communication frequency converter, dc circuit is the filter capacitor; Current model is the dc current source for communication frequency converter, transform the dc circuit filter is inductance.

4, why a frequency converter to the voltage and frequency proportional change?

Any of the electromagnetic torque motor is current and the result of the interaction of the magnetic flux, the current is not allowed more than ratings, otherwise it will cause the motor fever. Therefore, if the magnetic flux decreases, and electromagnetic torque will decrease, with load ability to reduce.

From the formula E = 4.44 * * * * * * * * * * * * * N K F Φ can see, in frequency control, motor magnetic circuit with running frequency is quite large in fX within the scope of the change, it is apt to make motor magnetic circuit, leading to serious saturated exciter current waveform distortion, produce peak serious high peak current.

Therefore, frequency and voltage in proportion to change, namely the change of frequency and the control of frequency converter, the output voltage motor flux keep certain, avoid weak magnetic and the phenomenon of magnetic saturation. This kind of control mode for fan, pumps and energy-saving inverter.

5, motor make labor frequency power driver, voltage drops the current increase; For converter drive, if the frequency decrease voltage decline, so current is not increased?

The frequency decrease (low speed), if the output of the same power, the current increasing, but in torque certain conditions, current almost the same.

6, the frequency converter to turn, the motor starting current, starting torque?

The transducer to run with the speed of the motor increased frequency and voltage, starting current is limited in 150% rated current (according to the different models, for 125% ~ 200%). Labor frequency power direct starting, starting current rated current for six to seven times, therefore, will produce the mechanical and electrical shock. Based on frequency transmission can smoothly starting (starting time become long). Starting current for rated current of 1.2 ~ 1.5 times, starting torque is 70% ~ 120% rated torque; With torque converter, enhance the function of automatic starting torque for 100% above, can take full load starting.

7, V/f mode is what mean?

The frequency decrease voltage V also falling proportionately to, this problem has set up a file in the answer four instructions. V and the scale of f is to consider the motor characteristics and predetermined, usually in the controller storage device (ROM) are several properties, can with a switch or scale plate choice.

8, proportional to the change, the motor f V and the torque how to change?

The frequency decrease is reduced in proportion to the voltage, then because exchange impedance decreases and dc resistance unchanged, will cause in the low speed to produce a tendency to reduce torque. Therefore, in the low frequency given V/f, to make the output voltage increase, in order to get some some starting torque, the compensation says enhance starting. Can be used in a variety of ways to implement, have automatic methods, choose V/f mode or adjust potentiometer method, etc.

9 in the prospectus, written on 60 ~ 6 Hz ac variable speed range, that is, so now in the following six Hz ac no output power?

In the following six Hz ac can still be output power, but according to the temperature of the motor and the size of the starting torque on the conditions of minimum use frequency, take 6 Hz ac motor output at this time around, can be rated torque and won't cause severe fever problem. The actual output frequency converter (start frequency) according to the model of 0.5 ~ 3 Hz ac.

10 for general motors, the combination of more than 60 Hz ac is in also calls for torque must, whether can you?

Normally when can't of. In more than 60 Hz ac (there are also more than 50 Hz ac voltage, roughly the same pattern) for constant power properties at high speed, require the same torque, must pay attention to the motor and converter capacity of the choice.