hi comrades,
im on process of designing a circuit for refrigrator guard which can damp the effect of fluctuations of electricity especially when the supply powers-backs before the system(cooling) get balanced due to previous situation of powerless
i.e the circuit should be capable of bringing enough time for the system to completely stabilize before allowing power to restart the process again...


-alot of regards for any suggestons!!!!!!

 

If I understand what you are asking for it looks like you want to delay power being applied after a power loss/return. You could use a processor to control the power return or you could use a delay relay perhaps.

 

thnks,, bt i got idea of using autoranging opamp. i wl try both alternatives

 

A turn-on delay relay is all you need. Don't know what an autoranging opamp would have to do with that.

How much delay do you want?

 

He wants 3 to 5 minutes. These modules have already been invented and can be had for less than $20. Wait until I go look something up.

It's called a, "delay on break" timer. Whenever the power goes low or stops, or the thermostat stops the compressor, the delay timer refuses to restart for 3 to 5 minutes. The insides and outsides look something like this:

 

Are these delay relays used to allow the compressor to mechanically 'unload' before the power is restored? to avoid starting the motor into a heavy load?

Is my understanding correct?

 

100% correct.

The delay on break timers start counting time when the circuit goes off. The delay on make timers start counting time when power is applied. The time delay allows the refrigerant to equalize pressures on both sides of the compressor so the compressor starts with equal pressures on both sides. Compressors will absolutely NOT start with 100 PSI difference. That's why air compressors have an unloading valve. The reservoir tank never returns to 0 PSI, but the compressor must fire into a 0 PSI cavity until the crankshaft gets some velocity.