Equipment Selection 

1. Selection of frequency converter

When selecting the type, we should first consider the operating conditions whether one or more motors should be started or stopped at any time during the operation of the frequency converter.

If the motor does not need to be started at any time during the operation of the frequency converter, it is not necessary to stop or stop the motor at any time. Then, when selecting the capacity of the frequency converter, only the rated power of the frequency converter is greater than the total power of all motors, and then the model can be amplified. In this case, when carrying out electrical design, we must ensure a principle: when the frequency converter is in the stop state, the contactor can be switched and the operation state of the variable frequency motor can be put into operation; in the operation process of the frequency converter, it is strictly forbidden to start and stop a certain equipment or multiple equipment separately.

If the motor needs to start and stop at any time during the operation of frequency converter, special attention should be paid to the capacity selection of frequency converter! Firstly, the total power of the motor that may be started and stopped at any time is counted, and then this power is multiplied by 5 ~ 7 (in the operation of the frequency converter, the motor started at any time is equivalent to direct starting, and the starting current of the motor is almost 5 ~ 7 times of the rated current). Finally, the sum of this result and the total power of the motor that does not need to start and stop with time is the theoretical power of the required inverter. If there are many devices that need to be started and stopped, then this power can be used as the selection power of frequency converter, and there is no need to amplify it again because it is difficult to start multiple motors at the same time. If there are few devices to start and stop, then this power needs to be amplified one more level to be used as the selection power of frequency converter.

2. Selection of AC contactor

For the motor that needs to start and stop at any time, it needs to be equipped with AC contactor. For the selection of AC contactor, the general selection principle can be followed - the rated current of the motor can be further enlarged to select the type.

3. Selection of thermal overload relay

In order to protect the safety of each motor and inverter, the thermal overload relay must be installed in the main circuit of the motor in principle. For the selection of thermal overload relay, follow the general selection principle - the rated current of motor is within the setting range of thermal overload relay.

matters needing attention

In the case of high-frequency converter and high-frequency drive current, if the leakage current of a inverter is too high, the current distribution may be too high. If the line is too long, an output filter is needed.