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Other Vintage Household Electrical or Electromechanical Items For discussions about other vintage (over 25 years old) electrical and electromechanical household items. See the sticky thread for details.

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Old 1st Aug 2017, 11:06 am   #41
PsychMan
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Default Re: Fridge compressor capacitors

I may well try that if I get the time.

In general are MOVs better suited for dealing with switch-off spikes for such an application? Its working fine with 2 bidirectional TVS diodes across the load, but not sure at this stage if that will continue. I do have some MOVs I could use instead, or possibly in parallel with?

My understanding is TVS diodes are fast acting, but may not handle as much energy as an MOV does. I may be overthinking this, perhaps the snubber across the contacts and the diodes across the load are enough for such a hefty relay....
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Old 4th Aug 2017, 9:36 pm   #42
McMurdo
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Default Re: Fridge compressor capacitors

I'd look at the datasheet for the SSR in question. Some already have built-in snubber components for inductive loads but those that dont usually have a suggested circuit.
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Old 5th Aug 2017, 8:23 pm   #43
PsychMan
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Default Re: Fridge compressor capacitors

It doesn't appear to have anything integrated based on the sheet. It's also zero crossing, which I understand aren't usually the best choice, but seem to be the easiest to obtain. In this case I got a decent quality crydom relay for 10, that would usually go for around 50. This is rated for 50A, so hopefully for my little fridge compressor it shouldn't be too stressed. It's also "snubberless", so I added my own.

Crydom have a paper where they mention the use of MOVs for inductive loads, but it also presents a few other options

From what I've read MOVs will absorb more energy, and for motor applications deal with the transient quicker, so I've now swapped the diodes for an MOV across the load. It's working well and fingers crossed it stays that way!!

It's been a fun project, and a learning experience. It's always nice when those factors coincide with giving something old a new lease of life
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Old 21st Aug 2017, 3:24 pm   #44
McMurdo
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Default Re: Fridge compressor capacitors

'Snubberless' usually means it doesn't need an external snubber.
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