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In addition to the basic logic of start, stop, forward, reverse and speed regulation, the control of frequency converter basically requires that the level state is effective, not the rising edge. Therefore, when using the button switch to control the frequency converter, it is generally necessary to use the button switch in the form of self protection.

1. Single switch start stop

The frequency converter can only give high level through the run terminal. The frequency converter can be started. When the switch is disconnected, the run terminal becomes low level. In this case, the self protection button switch can meet the start-up and stop control of the frequency converter. More switches can be used to reset the fault and receive rst. Of course, the non holding switch is not given by a separate potentiometer, At this time, the frequency can be given through the operation panel. Of course, the above logic can also be completed by PLC and other logic controllers.

2. Double switch for positive and negative start stop

Sometimes it is necessary to control the positive and negative rotation of the frequency converter. AC asynchronous motor can rotate any two phase lines at the output end of the frequency converter to reverse, but the operation is troublesome. The frequency converter has the function of reverse direct start control.

For example, the switch receives the forward rotation terminal (FWD, here is di1) of the frequency converter. At this time, the frequency converter rotates forward, and the switch of course chooses the hold type. Similarly, when another switch receives the reverse terminal of the frequency converter (some are rev, here is di2), the frequency converter will be in any case, and the switch is also holding type. When the switch is disconnected, the frequency converter will stop running. If there is no external potentiometer, the frequency value of the inverter can also be given through the panel.

3. One switch controls the start and stop, and the other controls the given speed

It has been mentioned above that one switch controls the starting and stopping of the frequency converter, and the other switch can actually be used for speed setting. The simplest is inching control. Some frequency converters, especially European systems, can also use multiple speed function ports or up / down setting, which is essentially the same as inching mode. No matter what method is used to control the frequency converter through the switch, it is essentially to give a certain high and low level to the I / O port of the frequency converter. If the frequency converter does not work, as long as the multimeter is used to measure the corresponding I / O port to judge whether the level signal is normal, you can know whether the line is connected, and then set the function of the port according to the manual.