How to prevent relay arcing using RC snubber circuits?

How to prevent relay arcing using RC snubber circuits?

In the Ohm’s law R = V/I, we apply the formula R = 0.5 (Vpk / ISW) and R = 0.3 (Vpk / ISW), where Vpk is the AC peak voltage ( 1.414 Vrms) and ISW is the rated switching current of the relay contact). To decrease the contact degradation due to arcing, we have to make sure the R value is minimum.

Which is the best snubber circuit for DC relays?

Ideally, a diode snubber is generally preferred for relays controlling DC load, while the second best are the ones that work with resistor and capacitor networks or using RC components. 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.

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.

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.

How to calculate resistor and capacitor size for snubber circuits?

You want to design something that clamps the transient that occurs when the switch driving the contactor coil opens. A voltage clamp is the better approach. Others have mentioned using a pair of Zener diodes connected in inverse-series. Although that is one approach, I don’t like that solution because the peak power capability is so low.

How does an AC analysis work on a snubber circuit?

The AC analysis will tell you the circuit conditions from the time when the switch is closed until the switch is opened. Once the switch is opened you take the “initials conditions” to be You then perform a transient analysis to determine what happens as the stored energy in the RLC loop is dissipated in the snubber resistor.

What should the snubber circuit value be for a solenoid?

The snubber circuit values will depend on the current drawn by the solenoid valves, and how often they cycle. For a start I suggest a 47 ohm resistor and a 0.1 Mfd 200 volt capacitor in series across the contacts.

How does arcing happen in reed relay switching?

How Arcing Happens in Reed Relay Switching A reed switch or reed sensor can be used for controlling an inductive device like a relay coil, solenoid, transformer, small motor etc. When the reed switch opens, the charge stored in the inductance in the device will force the switch contacts to a high voltage.

Why is RC suppression used in relay circuit?

RC suppression had the edge because of limiting the switch contact voltage exactly during switch opening when the contact gap is small. Furthermore, RC suppression can be implemented to lessen arcing and improve life in resistive loads.

Can a reed switch be used in a relay coil?

Since the principle of arcing may be the same in bigger relays also, the formulas used in reed relay could be also applied for dimensioning the RC networks for the bigger relays. A reed switch or reed sensor can be used for controlling an inductive device like a relay coil, solenoid, transformer, small motor etc.