Issue with relay and snubber

[venkates2218]

This is the snubber circuit which I used to run an 230VAC induction motor.
Input 230VAC is given to RL1-3(COMMON point of RELAY).But when we check the voltage in RL1-2(NO in Relay),Input voltage appears at this point also,even the relay in OFF condition.

Due to this,the motor is started to run even the relay in OFF condition.
How to solve this issue..?

[KlausST]

Hi,

Due to this,the motor is started to run even the relay in OFF condition.

Did you try this, or just guess?

Due to the capacitive impedance the current is limited to 34mA. If the motor and the load is that low power to make the motor move, then the snubber is designed too low impedance.

But I doubt the motor runs. As soon as you connect the motor the voltage will drop to a very small value.

--> It makes no sense to measure voltage on an high impedance node when no load is connected.
This is no real condition. Always measure voltage with real conditions.

Klaus

[venkates2218]

I tried it with real condition.
And if the relay is switched on and switched off means,the arc is forming between the contacts of relay.I used transparent relay to observe arc formation.
After switch off the relay also the load is running.Motor consuming 2.3A current..

[KlausST]

Hi,

then exactly show how you connected mains and motor. We don´t see this now.

It´s impossble to run more than 40mA via the capacitor... no way for 2.3A.


Klaus

[c_mitra]

It´s impossble to run more than 40mA via the capacitor... no way for 2.3A.

I strongly suspect that the capacitor is defective (failed due to high voltage spikes from the motor).

If your motor is taking about 2A current (say around 500W power or so) you should use a proper contactor OR a solid state relay.

[KlausST]

Hi,

I strongly suspect that the capacitor is defective (failed due to high voltage spikes from the motor).

I don't think so.
There still is the resistor that can't carry that 2.3A.

There is some systematic error, schematic error, measurement error....

Klaus

[Easy peasy]

did the resistor burn up? if not - your wiring is wrong ...

[venkates2218]

Like above image,wiring is done...

[KlausST]

Hi,

Impossible.
Please show a photo where we can see the wiring as well as the component values.

Klaus

[c_mitra]

There still is the resistor that can't carry that 2.3A.

I do not know how I overlooked that. Blame it on old age.

Of course you are right. Something is fishy.

[Akanimo]

Hi,

I would suggest you check for continuity of the relay terminals to determine the NO, C and NC terminals of the relay. It seems to me like you have mistaken NC for NO.

[Easy peasy]

or else a faulty relay ...

[venkates2218]

Running of motor during relay off condition is rectified,there is an issue in PCB LAYOUT.Sorry for providing wrong info.
Now it working fine,but the arc between the contact is still forming.

[KlausST]

Hi,

maybe chattering relay?
maybe snubber values don´t fit to the motor?
maybe a wire wound resistor in the snubber circuit?
Maybe the snubber is at NC contact while the motor is at the NO contact (or vice versa)?

--> Try a varistor/MOV in parallel to the snubber.

Klaus

[venkates2218]

This is PCB Layout for relay.
Input 230VAC is given at 2nd pin and motor is connected to 3rd pin.

- - - Updated - - -

Connected an 10D320K varistor across 2nd and 3rd terminals,but there is no changes.Still arc is forming between the contacts.

[FvM]

You're probably expecting too much. Snubber or varistor won't eliminate contact arcing completely, just reduce it.

[venkates2218]

You're probably expecting too much. Snubber or varistor won't eliminate contact arcing completely, just reduce it.

Contact arcing can't be eliminate completely..? or another method to eliminate arcing completely...

[Akanimo]

What resistor and capacitor values are you using?

[Akanimo]

What resistor and capacitor values are you using?

OMG! I'm sorry to ask this question. I should be asking what the current rating of the relay contact is.

[FvM]

G2R relays type is mentioned in the schematic, also fitting the photo. 10A 250VAC, suited for inductive load like motor.