One Freewheeling diode is a protective diode used in electrical circuits to protect sensitive electronic components from dangerous voltage spikes. Such overvoltages occur in particular when switching off inductive loads such as relays, contactors, solenoid valves, or DC motors.
Inductive loads contain coils that generate a magnetic field during operation. If the power supply is interrupted, this magnetic field collapses. Due to the physical property of the Self-induction However, the coil attempts to maintain the previous current flow. This can cause a high reverse voltage to build up within a very short time, which can damage electronic circuits, outputs, or switch contacts.
The free-wheeling diode is connected in parallel with the inductive load. During normal operation, it is in the reverse-biased state and has no effect on the circuit’s operation. Only when the load is turned off does the resulting reverse voltage take effect. The diode turns on and provides a closed current path for the induced current, allowing the stored energy to be dissipated in a controlled manner.
This significantly reduces dangerous voltage spikes and reliably protects connected components.
Typical Applications of Free-Wheeling Diodes
- Relays and Contactors
- Solenoid Valves
- Electromagnets
- Direct-current motors
- PLC outputs
- Digital Outputs from Measurement and Automation Systems
Advantages of Free-Wheeling Diodes
- Protection against induced overvoltages
- Extending the Service Life of Electronic Components
- Protection of Switching Contacts and Output Stages
- Reduction of Electromagnetic Interference
- A simple and cost-effective protective measure
Importance in Measurement and Automation Technology
Inductive loads are frequently switched in measurement, control, and automation systems. Without appropriate protective measures, the voltage spikes that occur during switch-off can damage outputs or cause malfunctions. The use of free-wheeling diodes is therefore one of the fundamental measures for ensuring reliable and long-lasting system operation.
In particular, when using measurement and automation devices to control relays, valves, or contactors, free-wheeling diodes should always be taken into account to provide long-term protection for the electronics against overvoltage.