Inverter startup method

When the inverter is not used, two contactors are required to control the forward and reverse rotation of the motor. However, this is no longer necessary after the inverter is used. The starting, forward and reverse rotation and braking of the motor are all controlled by the PLC. SB1 controls the forward start, SB2 controls the reverse start, and SB3 controls the stop (braking, OFF3 mode).

① Connect the PLC, inverter and motor as shown in Figure 4-1.

② Refer to the manual and set the inverter parameters according to Table 4-2.

Siemens inverter forward and reverse control wiring diagram

Siemens inverter forward and reverse control inverter parameters

③ Write the program and download it to the PLC, as shown in Figure 4-3.

Braking control of Siemens inverter

The braking methods when using the MM440 inverter include OFF1, OFF2, OFF3, compound braking, DC injection braking and external resistor braking. The MM440 uses the external resistor braking method, and its connection is shown in Figure 4-4.

① Select a suitable braking resistor according to the power of the inverter and the working conditions of the transport station motor. Please refer to the instruction manual of the MM440 inverter for details.

② Connect the inverter and the motor together as shown in Figure 4-4. Note that the switch contact on the brake resistor R should be connected in series with the coil of the contactor KM. In this way, when the brake resistor overheats, the thermistor on the brake resistor cuts off the power supply of the contactor KM, thereby cutting off the power supply of the inverter to play a protective role. ③ Verify whether the motor stops quickly when the inverter power is cut off or the stop "button" is pressed.