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  1. #21
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    Re: Issue with relay and snubber

    For 230Vac application a 275V MOV will start to clamp at around 700V - this is probably the best bet across the relay terminals, if you really want to snub it you will need 1uF 275Vac X2 cap and 22 ohm 3 watt resistor....



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  2. #22
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    Re: Issue with relay and snubber

    250VAC/12A Relay and 220 ohms resistor with K3-u47M305VAC capacitor



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  3. #23
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    Re: Issue with relay and snubber

    respectfully 10A into 220ohm at instant of relay opening is 2200 V so arcing will occur across relay contact ...



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    Re: Issue with relay and snubber

    But the load will be around 2.5A only...
    Shall I use the above mentioned values(22 ohm and 1uF capacitor) for this current rating.?



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    Re: Issue with relay and snubber

    the same formulae apply for 2.5A rms = 3.6Apk for 325V, R = 90 ohms, say 82 ohm, C can be 470nF 275Vac X2



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  6. #26
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    Re: Issue with relay and snubber

    You're probably expecting too much. Snubber or varistor won't eliminate contact arcing completely, just reduce it.
    Right. The total energy stored in the motor is being dumped on the capacitor and resistor. With a 1/2 HP motor, that can be significant.

    Because the load is supplied with AC, we do not know at what point the relay is getting turned off. Perhaps the relay can be turned off at zero crossing?

    I agree that the arcing cannot be eliminated.
    Last edited by c_mitra; 26th November 2019 at 04:55. Reason: spelling correction



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