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Can a diode be used to prevent a voltage spike from the coil of a relay?
The use of a diode in a relay circuit prevents huge voltage spikes from arising when the power supply is disconnected.
What is a coil suppression diode?
A coil spike suppression diode is a protection device across the contactor coil. Energizing the contactor coil creates a magnetic field that forces the solenoid arm to engage the contacts. When the contactor is turned off, the magnetic field collapses causing a back “voltage spike” that can damage the controller.
What is back EMF in relay coil?
If the coil is de-energized, the collapsing magnetic field in the coil as the armature moves away from the coil, generates a reverse voltage spike across the coil terminals – this is called “Back EMF (Electromotive Force).
How does a coil suppression diode work on a DC relay?
As seen in figure 3 below, the voltage across the coil when the relay is de-energized still has a conductive path through the suppression diode, similar to what is shown in figure 2. However, the magnetic field will not discharge until the reverse voltage reaches the avalanche voltage of the series zener diode.
What kind of diode do I need for a relay?
For an ordinary circuit, we recommend that you select a diode having a reverse withstand voltage of 10 times or more the circuit voltage. Make sure that the diode carries a forward current equal to or larger than a load current. We offer a lineup of relays for control panels, from which you can choose a relay with a built-in diode.
Where to place a flyback protection diode in a relay?
Tiny flyback diodes prevent huge flyback voltage from damaging your components. The placement of a flyback protection diode is rather simple; it should be placed directly across the relay’s coil. A schematic for a freewheeling diode circuit in a relay is shown below.
What is reverse voltage of Panasonic relay coil?
Fig. 2 shows a reverse voltage waveform in the case when there is no diode, and Fig. 3 when there is a diode. In the case when there is no diode, as shown in Fig. 2, a reverse voltage of 260 V is generated when the DC inductive load is cut off from the circuit.