How to Control the Forward and Reverse Rotation of a Frequency Converter with a Single Wire

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How to Control the Forward and Reverse Rotation of a Frequency ConverterReverse Rotation with a Single Wire

#### Hardware Connection
Connect an output point of the PLC (such as Q0.0) to the digital input terminal of the frequency converter, for example, the DI1 terminal of the frequency converter, through an intermediate relay (assumed to be KA1). This wire connecting the PLC output and the frequency converter input is the key wire for control.

#### Frequency Converter Parameter Setting
First, set the parameter of the operation command source of the frequency converter to external terminal control. For example, for the Siemens MM440 frequency converter, set the parameter P0700 to 2.
Then, set the functions of the digital input terminals. Taking the MM440 as an example, set the parameter P0701 to 1 so that the DI1 terminal is used for forward - rotation start; then set the parameter P0702 to 2 so that the DI2 terminal is used for reverse - rotation start. Since we are using only a single wire for control, we need to switch the forward and reverse rotation functions by changing the parameter settings related to this wire. For instance, reset the parameter P0701 to 9, which means setting the DI1 terminal to the function of bidirectional selection of the operation direction. In this way, different signal states input to the DI1 terminal can control the forward and reverse rotation.

#### PLC Program Writing
Use the programming software of the PLC to write the control program. When forward rotation is required, make Q0.0 output a high - level signal through the program. The intermediate relay KA1 is energized and closes. The DI1 terminal of the frequency converter receives the high - level signal, and the frequency converter operates at the set forward - rotation frequency.
When reverse rotation is required, change the output state of Q0.0 to a low - level signal through the program. The intermediate relay KA1 loses power and disconnects. The DI1 terminal of the frequency converter does not receive a signal. At this time, the frequency converter will switch to reverse - rotation operation according to the previously set bidirectional selection of the operation direction function.

The parameter settings and functions of frequency converters of different brands and models may vary. In actual operation, it is necessary to refer to the specific frequency converter manual for settings.#Virgin Islands#Turks and Caicos Islands#Tajikistan#South Africa#San Marino#Puerto Rico#Oman#Netherlands#Mexico#Macedonia#Kiribati
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