Electronics > Projects, Designs, and Technical Stuff
Relay with resistive rated contacts switching inductive load
Jester:
Can anyone hazard a guess as to how many operations could be expected from this relay: https://www.mouser.com/datasheet/2/418/NG_DS_RT2_1014-735741.pdf
When powering a 120V, 2A nominal refrigerator?
The relay will provide power from one of two sources, common to the refrigerator load.
I would think when the main source fails, that on power-up the refrigerator would not instantaneously start the compressor, and that the refrigerators control contact would actually switch the start current a moment (or later if it happens to be off).
On transfer back to the main source this little relay could be breaking the inductive compressor current.
Tomorokoshi:
Between 0 and 1.
Jester:
That seems overly pessimistic?
The data sheet for this particular relay only has a resistive rating, however looking at another relay with similar resistive rating that does provide an inductive switching rating, see below and appears to be capable of switching about 3A @125Vac Cos Φ = 0.4, 500,000 operations.
I looked at several contact curves and the rule of thumb seems to be about 1/2 rated (voltage and current) for Cos Φ = 0.4 or in some cases just 1/2 rated voltage for inductive load.
NiHaoMike:
The problem with inductive loads is voltage spikes when switching off, so add a MOV to the output or across the contacts to suppress that.
Jester:
--- Quote from: NiHaoMike on June 12, 2019, 06:32:09 pm ---The problem with inductive loads is voltage spikes when switching off, so add a MOV to the output or across the contacts to suppress that.
--- End quote ---
We do have a MOV.
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