Protect your critical motors/circuits

[BruceM]

Bill Rogers sent me a great tip:  the Magnecraft 831 Voltage Sensing Relay.

This DIN rail mounted relay will trip open or closed when your generator voltage falls outside of an adjustable range, and has an adjustable time delay (useful for big motor starting sags). 

I'm going to put one of these on my system- I'd especially like to protect my submersible pump motor which is 220 feet down the well.  If a bridge diode started to fail, or a belt started to slip, or any number of problems led to continued operation at well under or over voltage, the 831 would save my equipment.

http://www.magnecraft.com/products/831.pdf

Just thought I'd pass along this gem from Bill.  Thanks Bill!

Bruce M

[Doug]

There is another brand that probably is cheaper called "Carlo Gavazzi"...

Yes these work but its already been tested and done by myslef and others you can build your own relay with a RC network that will do the same for next to nothing but a little time and tinkering.

Doug

[gpkull]

good idea bruce downloaded but got a blank page.

[Jim Mc]

Worked for me.  Maybe you need a newer version of Acrobat...

What do these puppies sell for?

[Doug]

Too much in some cases Jim. Some of these things go for more than the cost of an ST head.
And as a side note I would like to warn people that the cheaper lines like the Carlo Gavazi don't like vibration. If its a modle manufactured by anyone with two circut boards soldered together at right angles its junk and will fail causing serious use of foul language and fist shaking as you try and find out what's causing a trip.

Doug

Just build an RC network and used a standard 24dc relay some diodes and if your feeling like it add an overvolt feature

[pigseye]

This seems like a great idea.  My well pump is 200 feet down too.  Cost me $2500 when i ahd the well redone and I don't want to avhe to do it again because of a generator or load issue.

Just to make sure I understand, you're adding a relay to the power to the pump.  Then if the voltage for the pump drops to low, the relay kicks in and kills power to the pump, thus saving the motor.  Then you manually reengage the relay when the generator can supply enough power.

Is that about it?

Thanks

[BruceM]

The 120volt version sells for about $57, the 240V version about $89, I think.

Doug, can you suggest a source/model for the Carlo Gavassi?

My only beef on the specs of the Magnecraft is that it isn't a "breaker" type.  In order to set it up as a manual reset, you'd have to add a latching type relay and a momentary switch for reset.  Alternately it could crow bar (short circuit) your circuit breaker via a (big) surplus solid state relay, which can handle surge loads better.

Yes, the low voltage relay drop out is easy to do via a variety of methods. One simple approach is using a DC relay, which means a transformer, diodes, then resistance, capacitance.  By the time you add high voltage cutout (second relay, RC), fiddling with time delay (C) so your big surge loads don't trip it, one of these doesn't look bad, price wise.  Depends on your time/$/junk box  situation.

[Doug]

Westburn Ruddy, Dixxon electric and Grant suply were my supliers. Westburn is probably in the US, but Carlo Gavazzi is big and sold world wide. Also look for Telemecanic brand I have no part number of value to you because the units I purchased were 600 v 3 phase. As far as I am concerned they are all junk with the exception of some of the 600 volt Allen Bradly units. All these things fail for the same reason vibration brake up the solder connections inside. Don't mount them on the Lister.

Doug 

[BruceM]

I agree Doug, mounting any PCBs/circuitry on the Lister is a bad idea. Just like the ST dog house- that dog bit me in just 12 hours of run time!

[Jim Mc]

...it could crow bar (short circuit) your circuit breaker via a (big) surplus solid state relay, which can handle surge loads better....

Still another option would be to crowbar across the field supply - much less power to interrupt.

[Doug]

You guys would be better served with suplus 3 phase contactor to pick up and drop the load.

Doug

[BruceM]

Checked out the C Gravasi stuff at Newark and Allied, very spendy ($170) and three phase, monitors each phase timing also. (Can't be used for single phase.)

Jim-  Opening the field coil for an emergency shut off might be ok- then you'd have to flash it to get started after correcting whatever is the problem.  For my ST3 head, it's very cheap to use an Omron relay on the full output since my setup is 230V single phase.  I already have that relay in place so that auto shut down will shed the load before shutting the rack and decompressing.

Bruce M

[Doug]

Never tried ther Omron stuff...
Never considered C.G. expensive from an OEM perspective as compared to toerh components.

Doug