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MOTOR PUMP CONTROL

In the Image... I am trying to put 30A 12V Relay OMRON G8P-1A4P 12VDC parallel to Push Start Button (Dual Starter control for 1HP Pump Motor). But every time relay picks up contact stick... Before using the Relay I was using 25A 24-480VAC SSR (Zero Crossing) but 4-5 of them failed due to large Surge / Inrush current. So I switched to mechanical Relay. But now the relay contacts are sticking.Do I have a weld current issue?

I also tried to add RC Snubber 0.1uF 600V + 66 Ohms but did'nt help.

Please suggest some idea of how I can avoid Arcing. Relay contacts are rated for 30A / 250VAC my load is max 20A for just 0.5-1 Second. Then contactor picks up and motor is operated through Contactor. No load is given to relay later on.Could I have underestimated the surge current?

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  • \$\begingroup\$ Do you have a reverse diode on the coil of the relay? \$\endgroup\$
    – Douwe66
    Commented Jan 26, 2016 at 9:51
  • \$\begingroup\$ Is the supply AC or DC, and what voltage level? Also what is the load specifically? What contacts actually weld together NC or NO? \$\endgroup\$
    – Andy aka
    Commented Jan 26, 2016 at 9:51
  • \$\begingroup\$ Supply is AC 230V. Load is 1 HP Single Phase Submersible motor. NO Contacts get welded together. Pulse is for just 0.5 Second. During this time Start Cap get's charged and current in Ameter is shown around 20A for just seconds... then Normally motor runs @ 7-8 Amp @ 230 VAC. But as soon as relay pickup.. contacts get welded together... i think due to high inrush current of start winding... \$\endgroup\$
    – KALPESH PATEL
    Commented Jan 26, 2016 at 10:03
  • \$\begingroup\$ contacts welding is caused by capacitive loads, perhaps you should use a contactor instead of a relay. \$\endgroup\$
    – Jasen Слава Україні
    Commented Jan 26, 2016 at 10:03
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    \$\begingroup\$ You're switching 1 HP @ 230VAC with a 30A @ 12VDC relay? \$\endgroup\$
    – Ecnerwal
    Commented Jan 26, 2016 at 12:08

1 Answer 1

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Capacitors & induction motors can both have HUGE initial inrush surge current transients that are often too short in duration to accurately show on most ammeters. An easy way to relieve your welding problem would be to install a 15A-20A ICL (Inrush Current Limiter) in series with your relay. ICLs are resistors with a highly negative-sloped resistance/temperature curve; this allows them to slow the instantaneous inrush current for that damaging fraction of a second, then reduce resistance & effectively short after a very short delay.

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