Thread: RPC phase loss protection

I’ve been running a 20hp Phase Craft converter set up for the last few years and it’s been flawless. I have a 60amp un-fused disconnect between the Phase Craft and the idler motor. I had the boys doing some cleaning/painting around the shop so I turned the power off to everything.

I turned the single phase converter power power back on but forgot to flip the idler disconnect switch. The 20hp idler made the awful noise it was supposed to for 1.5 seconds until the power was turned off.

I usually turn the disconnect off on my little Blanchard grinder but I must’ve forgot. I looked over and seen the white magic smoke rolling out the top of the magnet controller. It still works the way it’s supposed to....for now

I won’t repeat the idler disconnect mistake but I don't want phase loss power going to my machines again. The idler motor FLA is 48 at 240V.

1) Would a solid state overload relay placed before the 3 phase load center protect the idler motor and phase loss?

2) Is the relay install just hooking up the power in/out and the ground?

3) Does it matter which way the idler motor spins? I’ve read some conflicting opinions on that.

Thanks in advance.
Andy

You could put a 3 phase contactor on the output of RPC and wire the generated leg to pull the coil shut on that contactor. That way if RPC is not generating power the contactor is open an no power goes through.

Use the disconnect between the Phase Craft and incoming single phase power. Connect the idler directly to the converter with a contactor with a overload block that has
phase loss detection. It doesn't matter which direction the idler rotates.

Originally Posted by Hobby Shop

I’ve been running a 20hp Phase Craft converter set up for the last few years and it’s been flawless. I have a 60amp un-fused disconnect between the Phase Craft and the idler motor. I had the boys doing some cleaning/painting around the shop so I turned the power off to everything.

I turned the single phase converter power power back on but forgot to flip the idler disconnect switch. The 20hp idler made the awful noise it was supposed to for 1.5 seconds until the power was turned off.

I usually turn the disconnect off on my little Blanchard grinder but I must’ve forgot. I looked over and seen the white magic smoke rolling out the top of the magnet controller. It still works the way it’s supposed to....for now

I won’t repeat the idler disconnect mistake but I don't want phase loss power going to my machines again. The idler motor FLA is 48 at 240V.

1) Would a solid state overload relay placed before the 3 phase load center protect the idler motor and phase loss?

2) Is the relay install just hooking up the power in/out and the ground?

3) Does it matter which way the idler motor spins? I’ve read some conflicting opinions on that.

Thanks in advance.
Andy

Everything you need is already installed and paid for.

"Conventional wisdom" is to put a(ny) mag-starter's "hold in" contact on anything BUT the "generated leg". Which is actually MORE than stiff enough to hold-in if your rig is worth a damn. Decent idler, reasonable match to the load, a Phase Craft is good enough and will be.

So do the opposite.

Put each mag-starter hold-in contact path - or its control transformer - intentionally ON the generated leg.

Then.... No generated leg, no start.

Loose the leg or drive it too low? All stop. Inherently.

No extra players -solid state or otherwise - to go wrong.

That isn't actually a BAD thing.

Likewise, no fuses. They can trip but one leg at a time, potentially leaving two hots.

"COMMON TRIP" circuit breakers, please instead.

ANY leg misbehaves? ALL are interrupted.

Want "bells and whistles" on the cheap? Three lights. One each phase. Better yet? Three meters, one each phase.

Guild THAT lily? Meters for BOTH of Voltage and Current.

Compamy-funded cremation as a "retired operating engineer" for any rodent as gets into the works and fries his ass to nought but carbonized skeletal carbon trails across the terminals?

It HAS been done!

480 VAC input of an ancient 400 Amp Linde Dee Cee stick welder, first time our Union Local held the wake. Poor bugger must have been livin' on beans, ramps, and pickled eggs, the stench his explosive retirement left all up and down the machine-hall.

Originally Posted by thermite

Likewise, no fuses. They can trip but one leg at a time, potentially leaving two hots.

I make no claim for this story. It circulated about 30 years ago. A salesman was calling on a plant electrician and noticed some disconnect boxes that looked like they had been dynamited. The electrician explained that they had a pump house in a nearby lake, out in the middle, so it often attracted lightning strikes. Often that would blow a fuse and the motor would burn up single phasing. The electrician said that when a motor came off the line, he wanted it all the way off, so he used fuses with replaceable elements and filled them with gunpowder, which removed all the fuses.

To be a little more serious, which I have been known to do in rare weak moments, there are phase loss detectors on the market that detect the loss of any phase.

Bill

Originally Posted by 9100

I make no claim for this story. It circulated about 30 years ago. A salesman was calling on a plant electrician and noticed some disconnect boxes that looked like they had been dynamited. The electrician explained that they had a pump house in a nearby lake, out in the middle, so it often attracted lightning strikes. Often that would blow a fuse and the motor would burn up single phasing. The electrician said that when a motor came off the line, he wanted it all the way off, so he used fuses with replaceable elements and filled them with gunpowder, which removed all the fuses.

Can't call that "common trip" as it is a most UNCommon trip. 'Bout on a par with Capsaicin, USP in K-Y jelly..

To be a little more serious, which I have been known to do in rare weak moments, there are phase loss detectors on the market that detect the loss of any phase.

Bill

Surely there are.

They call them "burnt up motors".

[QUOTE=thermite;3499777]Can't call that "common trip" as it is a most UNCommon trip. 'Bout on a par with Capsaicin, USP in K-Y jelly..

Always turn the light on in the bathroom. So you don't grab the ben-gay instead of the KY.

phase loss detection - Google Search

Originally Posted by thermite

Can't call that "common trip" as it is a most UNCommon trip. 'Bout on a par with Capsaicin, USP in K-Y jelly..

Originally Posted by jim rozen

Always turn the light on in the bathroom. So you don't grab the ben-gay instead of the KY.

THIS lot of careless Old F***s?

More likely to be Loctite, RTV, or Cherry Go-Jo!



The CHALLENGE is remembering which one goes WHERE, WHEN, and WHY!

Just get one of these:

ICM Product Details - ICM401

Thirty bucks on Amazon. ICM makes some handy stuff!!!

Originally Posted by DaveKamp

Just get one of these:

ICM Product Details - ICM401

Thirty bucks on Amazon. ICM makes some handy stuff!!!

I prefer the ICM450, if you have some panel space to place it. The built in voltage meter is a plus, has line and load side protection, if required. Wide voltage range of power and control circuit voltages, and programmable which makes it handy to adjust for an unbalanced RPC output, and able to change the unbalance limit.

I have obtained several used units on auctions sites, for a fair price, and they all worked fine. But take a browse at the product downloads, at the bottom of the page, to see if it meets your needs.



SAF Ω