How are snubber circuits used to protect relay contacts?

How are snubber circuits used to protect relay contacts?

In this post we elaborately discuss regarding the many kinds of snubber circuits using resistor/capacitor, diodes, varistors, and also learn which of these topologies is the most efficient when it comes to protecting relay contacts from sparking and fusing?

What is the resistance of a snubber circuit?

The moment the contacts open, current will flow to the inductive load through the snubber. Let’ say the load if a motor or a Solenoid, the release time of the relay contacts will be increased. You can choose a resistance value of 0.5 to 1 Ω per 1 V of contact voltage.

Can a RC snubber be used across an inductive load?

If the RC snubber is placed across the inductive load, the arc suppression benefits of the RC snubber may diminish as distance increases between the switch contacts and the load, as wiring may be seen by the contacts as an inductance, and may still experience arcing. Evaluate if this applies to your application.

How does a snubber connect to a motor switch?

If you look at your circuit you’ll note that in both cases the snubber connects from the motor-switch connection point to one leg of the mains. If the mains impedance is low at the spike frequency (-ies) then both are about equivalent. The circuit current continues instantaneously at switch off.

Are there any disadvantages to using RC snubber?

While attaching the RC snubber across the switch contact is ideal, there is a huge disadvantage because this creates a current path to the load when the switch is open. If the snubber is installed across the load, it eliminates the current. However, changes in the connections and source impedance can affect the efficiency of the arc suppression.

Which is the best snubber circuit for AC and DC?

Varistor type Snubber This kind of suppressor is suitable for use with both AC and DC circuits. The varistor circuit avoids a high voltage from being channelled across the contacts by employing the constant-voltage properties of the varistor. Furthermore, this type of circuit also relatively increases the release time.

When to use a snubber circuit with a diode?

Diode +Zener diode type Snubber When a Zener diode is connected in series with a diode type suppressor, the circuit will reduce the relay contact release time. Commonly, this happens in scenarios where the release time of a diode is very slow. This type of suppressor is also not suitable for an AC circuit but good for a DC network.

What should the resistance of relay contacts be?

Let’ say the load if a motor or a Solenoid, the release time of the relay contacts will be increased. You can choose a resistance value of 0.5 to 1 Ω per 1 V of contact voltage. As these values rely on many factors including the load properties and deviations in characteristics. You can verify the values for R and C by experimenting.

Which is the most effective relay circuit DC or AC?

That said, in an AC circuit, a varistor or RC network happens to be the most effective. This type applies to both DC and AC circuits. However, the load impedance has to be lower than the RC circuit impedance when utilizing the relay for supplying the AC voltage.