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Biodiesel => Biodiesel equipment => Topic started by: 1958steveflying on April 23, 2013, 11:55:53 PM

Title: SSR gone down !
Post by: 1958steveflying on April 23, 2013, 11:55:53 PM

My second SSR has gone down, this one went live to earth so popped the fuse. Anyone point me to a good supplier ? I need to make up a couple of new control panels so looking for 4 with heat sinks. 

Title: Re: SSR gone down !
Post by: Rotary-Motion on April 24, 2013, 06:03:05 AM

what makes/models have you used so far?

Title: Re: SSR gone down !
Post by: Tony on April 24, 2013, 08:57:12 AM

You're best off with Opto or Crydom SSRs.  And make sure they are properly heatsinked to something (with thermal paste!).

Is the one that failed just switching an immersion, or are you switching motors too?

In the case of motors, because they are reactive loads you need a snubber in the load circuit to prevent damage to the SSR output stage.  Some SSRs include a snubber but some don't, and those are only good for resistive loads like immersion elements.

Think of it like this, when the motor is driven, it it taking power, but when you switch it off it is still spinning and starts to generate power as it winds down (much like an IMAG generator).  This power has to go somewhere and your poor SSR is where it ends up - pop!

Title: Re: SSR gone down !
Post by: Jamesrl on April 24, 2013, 12:15:45 PM

Tony, can you recommend a snubber suitable for 375W pump motors, typically Tam type.

Title: Re: SSR gone down !
Post by: Tony on April 24, 2013, 12:18:31 PM

It's very difficult to calculate the correct values for a snubber without some more technical detail on the pump motor or characteristics for it, but I'm expecting that an "Opto 22" SSR would be adequate as it has a built in snubber for switching things like motors.

Title: Re: SSR gone down !
Post by: Jamesrl on April 24, 2013, 12:28:24 PM

Cheers.

Title: Re: SSR gone down !
Post by: 1958steveflying on April 24, 2013, 05:46:41 PM

Quote from: Confucius on April 24, 2013, 06:03:05 AM

what makes/models have you used so far?

Initially both in my processor were Chinese, one died very soon after fitting which was replaced by a Crydom, this second Chinese one has lasted over 5 years.

Looking for Crydom or similar if I can get them at a sensible price  !

Title: Re: SSR gone down !
Post by: 1958steveflying on April 24, 2013, 05:49:10 PM

Quote from: Tony on April 24, 2013, 08:57:12 AM

You're best off with Opto or Crydom SSRs.  And make sure they are properly heatsinked to something (with thermal paste!).

Is the one that failed just switching an immersion, or are you switching motors too?

 

Just switching immersion Tony.   I have 2, one reacting to oil temperature in the reactor and the other to water temperature on the twin cone heater.