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1 to 3 phase problem

stevet

Aluminum
Joined
Mar 31, 2008
Location
western mass
The electrical setup I have in my shop is as follows.
I have a static phase converter that starts a 3hp 220v 3 phase motor ( pony motor)
I’ve wired that motor to a junction panel and connected my surface grinder with separate vacuum motor as well as my band saw to that panel.
Both machines start and run fine.
I just wired my series one Bridgeport to the same panel and when I start the Bridgeport it draws a high load and the motor is louder than expected, sort of a groaning humming sound.
Once the motor is up to speed it quiets down. It’s a 1hp induction motor and I start it with no load, slacken the V belt
The motor is a Fairbanks, I believe it’s called a pancake motor, and it’s rated at 3.8A at 220v.
Any ideas what might be wrong.
Thanks, Steve
 
You don't have a Pony motor, a Pony motor is a single phase motor used to start a 3 phase motor to be used as a RPC. The static converter you use to start the 3 phase motor is it still connected after the 3 phase motor started?
 
A 3HP converter (idler) should run and start a 1 HP motor.

The pancake motors are a bit odd, and may draw more current than expected at start. Some regular motors are also "pigs" to start.

Yes, another 3 phase motor also running no load can act as an auxiliary idler.
 
Thanks thermite and JST.
I’ll try running the saw and surface grinder for additional starting help, take 2 aspirin and give it a whirl.
I’ll repost tonight after the test.
 
I've never had a problem starting B'port pancake motors. Have a pancake motor on my Toolmaster that has variable speed with a 3HP RPC. Connected others for friends without problems. However I never had a static converter and RPC both running together to create 3 phase. If the Static converter and RPC motor are running together when you to start the BP I would try starting the RPC (motor you called pony) then shutting down the Static converter and let the RPC "single phase" then try starting the BP.
 
Oh! I didn't know it was a single unit. I assumed by him saying he wired a 3 phase motor to the panel that the "Pony" as he called it was an RPC and Static converter used as a starter. I would assume it will have all the bells and whistles needed to automatically start a 3 phase motor and if it too were connected to a 3 phase panel easily disconnected by flipping a breaker allowing the 3 HP motor to single phase once started by the static converter.
Jim has a point, check to see if BP motor is wired for low voltage. Unloaded motor as he is loosening the belts will start and run on 1/2 voltage. Another thing to check is the connection. If as most BPs have a SO type cable for connection and 4 wire colors being Green, White, Black and Red it was very common that White was used as ground and Green as 3rd power. Prior to green wire White was coded to be neutral or ground. I have found many machines wired using White as ground connection and Green for Power.
 
As said to assume is to make an ass of self! But the OP stated he added the 3 phase motor to the 3 phase panel. I'm thinking he had the static converter connected to the panel to operate the other machinery and later added the motor when he wanted to add the BP. I assumed what he did, my bad! But the OP was not very clear as to how the system is wired and why I originally asked if both were connected at the same time. There is no mention of the Static converters size.
 
A "static converter" is generally fine for starting an idler. All the relays etc normally in the fancy box are really just doing the same thing..... starting a 3 phase motor to run on single phase.

In fact, one of the companies that make both SPCs and RPCs has an app note on their site for doing just that. It can be a simple way to get going, workable, even if perhaps not the best.

The diagram is at the end of this link: https://phaseconverters.phase-a-matic.com/Asset/SIS-UL 2021.pdf
 
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I have been waiting to see the results of the OP's test. Turning on more 3 phase motors and let them idle will add to the 3HP RPC. I do it all the time! On the other hand Jim's suggestion to check voltage wiring was great and I feel it might be the problem. But there is a possible other problem that will become greater if more motors are turned on to increase RPC HP. Static converters are designed for a given HP and are automatic in that changes are made electrically as the motor they are supplying comes up to speed. Start Cap is removed, a run cap maybe be used as well as possibly balance caps. But if HP is increased the static converter might not function correctly. I don't know the size nor internal function of the Static converter, maybe the 3HP motor was added to run the BP motor. The fact that it starts the low HP motors on the surface grinder and band saw does indicate connection correctness but not function correctness. The Static converter might as connected work with lower HP but not as HP requirement is increased. That will show up when he tries adding other machinery motors HP to increase RPC motor size. I would think using a static converter as a way to start an RPC is OK but if the system is connected to a number of different motors the static converter should be disconnected once the RPC motor is running and more so if the size of the static converter is equal to or slightly less than the 3HP RPC.
 
Sorry for the follow up delay. The holidays are to busy a time for me to spend in my shop.
Checked the wiring on the BP motor and it is wired correctly for low voltage.
I tried running the saw and surface grinder with the idler then starting the BP and that didn’t seem to make a difference.
Then I ordered a couple of run capacitors and wired them in.
Not much difference with the BP starting but the voltage is closer to balanced and the idler motor runs much cooler.
Maybe this is just the way the BP motor at home is going to sound at start up and I’m use to my other BP at work snapping to instant, full speed.
The one at work is on true 3 phase power.
 
It sounds like... to me... that there's something not-quite-right.

My gut says that somewhere, there's a wire that isn't nail'd down quite tight enough, or it has a fair amount of resistance in it... or the pancake might have spent too much time in the pan.

Mebbie disconnect the pancake's wires and give it a visit from an ohmmeter, mebbie it'll show something awry?
 








 
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