Cabinet Cooling and Temperature Monitoring example

This example shows a typical electrical cabinet cooling circuit, including the power supply and control of the cabinet fan, as well as temperature monitoring through the PLC.

The cabinet fan -M1 is supplied through the circuit breaker -F2 and controlled by the thermostat -TSW1. The thermostat is set to a defined temperature of 35°C. When the cabinet temperature reaches the setpoint, -TSW1 switches the fan circuit, allowing -M1 to operate and cool the cabinet.

The fan -M1 is connected to the protected supply and also has a PE connection, providing the required protective earth connection.

The circuit breaker -F2 also provides a feedback signal to the PLC through its auxiliary contact. This signal is connected to PLC input I200.4, allowing the control system to monitor the status of the fan's protection circuit.

A second thermostat, -TSW2, is used to monitor the cabinet temperature. When the cabinet temperature reaches its defined setpoint, -TSW2 changes its contact state and sends a signal to the PLC input I200.5. This allows the PLC to detect that the cabinet temperature has reached the specified limit.

This arrangement provides both automatic cabinet cooling and temperature monitoring, while allowing the PLC to monitor the status of the fan protection circuit and receive a temperature warning signal when the defined temperature limit is reached.