3 phase motor disconnected - everything fried

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designer82

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Bit of a strange situation where a building owner has a 3 phase electrical system (for educational/assembly building roughly 18,000 sq.ft). They installed a 3 phase motor (I assume it's actually a motor based on what owner said). No one actually knows why this "motor" was installed. They assume it was installed to balance the building loads.

Motor was installed 10 years ago. Recently, building inspector told them this motor is of no use and to shut it off. So they did and it fried all sensitive type branch circuits, such as hvac controllers, lighting equipment, etc. etc.

Any thoughts?

(my thoughts are that the shut-off caused over-voltage spike that fried everything)
 
not to gripe at you, but I've never heard of installing a motor to balance building loads. why not just a resistor bank if you want to waste money on electricity?

its possible one has nothing to do with the other.

how big is the motor?

what type of motor?

how was it turned off?

was it turned on and off more than once?

how is it connected to the devices that fried?

are there surge protectors?

ask the building inspector since, in his infinite wisdom, it wasn't needed.
 
Any chance it was a rotary phase converter creating 3-phase from an actual single-phase service? Purely a guess. That could certainly ruin some equipment, though I don't know off hand why it would particularly effect "sensitive" items.
 
Maybe the "motor" was set up as a rotary phase converter to create 3-phase on a single-phase service. Not that it makes much difference, but perhaps they needed it for "educational" purposes such as instruction in HVAC, etc.
As the OP mentioned, there could have been an overvoltage spike when it was shut off, especially on the "manufactured" leg. Electronic controls should not be put on the manufactured leg, but perhaps they did it anyway.
I see that Electromatic just posted the same thing.
 
Three phase motors are turned on and off all day long in many facilities, like offices, and sensitive loads are never 'fried'.

Please provide more details.
What voltage?
What size service?
What size device was turned off?
What business does a building inspector have in regards to customer loads?
 
designer82 said:
Bit of a strange situation where a building owner has a 3 phase electrical system (for educational/assembly building roughly 18,000 sq.ft). They installed a 3 phase motor (I assume it's actually a motor based on what owner said). No one actually knows why this "motor" was installed. They assume it was installed to balance the building loads.
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I have have never heard of anyone installing a motor to balance loads. It just serves no purpose.

designer82 said:
Motor was installed 10 years ago. Recently, building inspector told them this motor is of no use and to shut it off.
Click to expand...
The owner needs to sue whomever the building inspector works for. It is not his job to make such calls.

designer82 said:
So they did and it fried all sensitive type branch circuits, such as hvac controllers, lighting equipment, etc. etc.

Any thoughts?

(my thoughts are that the shut-off caused over-voltage spike that fried everything)
Click to expand...
It seems unlikely. As someone else mentioned maybe it was actually a rotary phase convertor. But no idea why that would fry anything.
 
drktmplr12 said:
... I've never heard of installing a motor to balance building loads. ...
Click to expand...
I have heard of unloaded, over-excited synchronous motors being used to improve power factor.
But not c.2013, and not in an educational/assembly building.

Are you sure all those devices are actually fried? One possibility is that it's a rotary phase converter, and turning it off de-energized everything connected to the third phase.

Your puzzle has pieces missing. Send photographs.

need-more-input.jpeg
 
I hooked up a RPC for some woodworking equipment and the instructions for the equipment specifically stated not to use the mfg leg for controls, which the phase was marked on the connection terminals.
 
ptonsparky said:
Ditto to all the roto phase, but how in the world did they manage to size it properly? Sensitive electronic equipment along with roto phase just doesn't sound like a good match to begin with.
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My guess would be that 3 phase was needed for a piece of equipment, the RPC was installed and wired through a small panel. Eventually, single phase loads got added to that panel without regard to proper practices.

Probably just sized for the original application. If sized for starting a motor, it would have excess capacity most of the time.
 
The device mentioned by @drcampbell in post 9 is called a synchronous condenser. An overexcited synchronous motor has a leading power factor and can be used to supply kVARs for power factor correction.

A rotophase can be used to develop the third leg to start three phase motors. But once those motors are running, if they are lightly loaded, they will also act to strengthen that third leg. On one of the electrical discussion boards, someone called ?hillbillysawmiller? described starting a small rotophase, which was then used to start the smallest saw. This was then left unused and spinning freely, while the next saw was started, working up to the largest saw they needed to use.

I could imagine one unloaded motor being shut down, thereby taking out other equipment...but I can't see how that would have survived random power hits over time.

Jon
 
drcampbell said:
I have heard of unloaded, over-excited synchronous motors being used to improve power factor.
But not c.2013, and not in an educational/assembly building.

Are you sure all those devices are actually fried? One possibility is that it's a rotary phase converter, and turning it off de-energized everything connected to the third phase.

Your puzzle has pieces missing. Send photographs.

View attachment 2565075
Click to expand...

Synchronoss Condenser. But in a facility that small? I've only seen them at utility scale, or in very large facilities
 
Likewise. I've only seen them in industrial settings where there was more than a thousand horsepower worth of induction motors installed, not in an educational/assembly building.

But there's a first time for everything, no matter how absurd.
 
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