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Thread: motor only hums, wiring help
11-22-2010, 04:39 PM #21
Hi I'm back
The low buck, old tech, SIMPLE solution to your situation if your motor is truly wound for three phase operation is still a static type phase converter that will cost in the neighborhood of $150.00 and be very non electrical genius friendly to hook up using 220 volt single phase as a supply.
I have and currently use all of the above mentioned choices to power my three phase equipment but I started out with a lowly static converter and gradually grew more familiar and comfortable with three phase stuff with experience.
If it proves out that your motor is toast for some reason let me know and I will sell you a good one for $150.00 and then you will know exactly what you have and how to wire it. As a matter of fact we could swap yours for one of mine for a few bucks less if you like.
11-22-2010, 04:49 PM #22
Leigh, what it two phase power?
Hi Leigh, just a little insert to this thread of electrical motor intrigue is the question what the heck is two phase supply.
I am not cracking wise when I ask that because that is what I was hoping to learn from this thread when you pointed out that the nameplate was for Two Phase and not three phase
I know the shell on that old pancake motor may well be from the 50's and Fairbanks-Morse had been around for a while then so no doubt they were used in industry as Two Phase supply motors, does anyone know how that worked?
11-22-2010, 05:01 PM #23
Wikipedia to the rescue
I should have thought to check Wikipedia for some info as they sure seem to have lots of reasonable answers
Two-phase electric power - Wikipedia, the free encyclopedia
As Leigh mentioned it is old school stuff and interesting to see why they did it that way
Sorry to be talking to myself (three posts in a row) but my fingers get ahead of my aging brain occasionally and I can't help it.
11-22-2010, 05:37 PM #24
11-22-2010, 09:24 PM #25
is there any way to confirm without a doubt that my motor is a 3 phase unit ?
11-23-2010, 12:45 PM #26
Steve, I can't see the pictures, so excuse me if the answer is obvious. What does the motor plate say with regard to whether it's a 3 phase or a 1 phase motor? IF it's a single phase motor, there should be a bump for a start capacitor on the side of the motor. IF it's a single phase motor, the typical cause of the motor humming rather than starting is a problem with the start circuit - either a bad capacitor, or a dirty starting switch.
IF it's a 3 phase motor, you have three choices. You can make your own "static" 3 phase converter by adding a capacitor in the circuit; you can make a rotary phase converter; or you can buy a variable frequency drive.
Instructions for all three choices are in the forum dedicated to phase converters and transformers here at PM.
11-23-2010, 02:30 PM #27
11-23-2010, 03:20 PM #28
The nameplate says '2 phase' but the motor connections are typical for a dual voltage three phase motor. Your diagram shows the proper wire numbers and connection for low voltage, 220 volts three phase.
In the picture on your first post you can see part of the windings. They appear new and shiny with modern varnish and fiberglass/cambric wrapping and ties, not things from a 2 phase era in my estimation.
I think the motor is obviously three phase and has probably been through a motor shop recently, especially if the wires have good readable tags on them.
IMHO, the only thing '2 phase' about this old beast is the brass motor nameplate itself.
If the motor was in a flood it must be dried out and megged before you hit it with the juice or the magic smoke will escape.
That's my two cents on two phase!
11-24-2010, 08:30 AM #29
If the motor has 9 wires I am 99.9 percent sure it is 3 phase. Get a small static phase converter rated for that size of motor and try it.
11-24-2010, 08:52 AM #30
I say it never ran; the previous owner gave up.
Unless Niagra Falls is (still) producing 2-phase power, I doubt that motor will ever run at full power.
Here is an excerpt from a post by DaveKamp:
Your'e right, SW... it WAS a Niagra thing... there are other places that had it, isolated oddities, really, as 3-phase made it obsolete the very moment it was tested. FWIW, there are OTHER 'oddities' out there, like 25hz power... had to deal with that out on sections of the Northeast Corridor, where my trains had switchgear and transformers built specifically to run both 25 and 60hz. There never was bona-fide two-phase in Houston that I'm aware of, but John Oder knows better than I. It ain't something you can just slap on a pole... it starts with a generating plant BUILT for 90-degree phase separation, and continues with switchgear and transformers built-to-plan. There are VERY few places in the US that have it.
Here is a excerpt from a PM I had with DaveKamp:
Nope- two phase power requires AT LEAST FOUR wires, plus a ground!!! You have A, B, C, and D... where A and C are 180 degrees out of phase (like 240 single phase, but with no center-tap), and B and D are 180 degrees out of phase. In order to get 120v, you needed FIVE wires, plus ground.
What they did... was take a four-pole generator, and split out two poles to one feeder, and the remaining two poles to another.
See, the whole idea was to give an induction motor the starting torque of a DC motor...
But the best answer was THREE phase... where you only needed four wires... three hots, and a ground... (for Wye), or... only 3...(for Delta).
Turns out that having 120 degree phasing, was every bit, if not more satisfactory, than running 90-degree intervals... because the torque-angles of an AC induction motor under slip... is about 60 degrees... hence... 120 degree intervals.
This ALSO made the amount of pole-top transformers and wiring a whole lot simpler, easier to install, and less expensive than three-phase... so in the end, 3 phase won because it was every bit as effective, and 28% cheaper.
Give up on that motor, or ask DaveKamp
That motor is a hundred years old.
11-24-2010, 09:17 AM #31
I think it ran....I think it's be rewound and it guts are a standard 9 wire, three phase motor. Only the nameplate is 100 years old.
Jstanley6787 has the right idea.
11-24-2010, 10:06 AM #32
Power up one leg (any two groups of wires) of that alleged three phase motor with 250 (single phase) volts.
Give the shaft a spin, one direction, or the other.
Does the motor start to rotate and keep rotating?
If yes, then put a voltmeter across all possible pairings of those three groups of wires.
Do you have (roughly the same) voltage across all possible pairings? If Yes, then the motor is three phase, and you are now running it as a rotary converter. It could provide adequate three phase for another, smaller, three phase motor, but that's it; it cannot generate any rotating force.
11-24-2010, 10:49 AM #33
The static converter provides a phase-shifted voltage on the third leg during startup, then it disconnects that leg and the motor runs on the other two legs (i.e. single-phase). It can deliver about half the nameplate hp in that configuration.
I have a Bridgeport set up with a static converter and it runs fine.
Last edited by The real Leigh; 11-24-2010 at 12:58 PM.
11-24-2010, 02:07 PM #34
Simple test to see if it will run on 3 phase
The consensus seems to be that it's wired internally as a 3 phase motor despite the name plate ( I finally got to see the photos on my home computer last night - they're not visible when I use the wireless network where I'm posting from currently.)
You can run a 3 phase motor on single phase power without any capacitors or start switches, but it won't have its full power. Nevertheless, you can test your motor by giving the rotor a spin before turning on the electricity. If it continues to run, you've probably got a 3 phase motor. I suspect you can't give the rotor enough spin if you leave it in the mill, so that's why I think you'll have to take it out to do the test.
Take the motor off of the mill and somehow attach it to a board, so it can't roll around the shop once it starts. Some big blocks of wood screwed on either side as wedges with a rope between them over the top of the motor may be enough. Connect the wires as you did when it hummed. Wrap a rope around the shaft like you would on an old 1950's pull start lawn mower. Pull the rope briskly to spin the rotor and immediately turn on the power. If it continues to spin, you've probably got a 3 phase motor.
Assuming it runs, the cheap (temporary because you'll eventually want the full power) next step is to add a start capacitor in the circuit, with the start capacitor controlled by a push button in the circuit. In this second variation, you hold in the start button and turn on the power. When the motor comes up to speed (about a second) you let up the button to disconnect the start capacitor. The diagrams for the wiring of the start capacitor and the size start capacitor to use can be found in the forum on Transformers and Phase Converters.
Building a rotary phase converter isn't much different than doing the above although in that stage you'll add a few oil filled run capacitors to balance the current.
11-24-2010, 04:10 PM #35
I'm thinkin' it IS a two-phaser. It MAY have been re-wound at some point or another, if it was a reputable shop, they would've made a new plate...or he may have actually had a 2-phase system in his shop, or (considering there's still a few places around that have 'old' systems) something wierd (corner-grounded anything)...
but look closer at his dataplate...
Steve: My suggestion here is to:
1) find a surplus 2hp 3-phase motor, make an adapter plate and toothed-belt sheave adapter
2) Get a toothed-belt sheave for the SPINDLE side, and replace the step-pulley
3) Slap a used-surplus 5hp VFD on it...
and call it done.
I think my belt, sheaves, etc., were under $50... the VFD was under $100... misc materials probably under $25. Took a little shop time, but well worth it.
11-24-2010, 04:27 PM #36
This is what the internal layout looks like:
Internal windings are 1-5 and 7-3, and at a 90 degree relationship, 2-6 and 8-4.
That being the case, if you disconnect ONE set of coils, apply power (it'll hum) then give it a spin by hand, it'll probably spin up.
And if you wanna use this motor, you could probably power one set (say 2-6/8-4) through a motor run capacitor and get it to start and run that way... at a slight power penalty...
You can verify the validity of the wiring scheme by disconnecting ALL motor leads, and putting an ohmmeter or continuity tester across EVERY ONE, and finding out WHICH wires have continuity.
If it matches my diagram, you'll have continuity just the way the diagram indicates.
If it's 3 phase, it'll match some other diagram, and if it's three-phase with Y-connected center, you'll find that THREE of the wires have mutual continuity.
11-24-2010, 04:35 PM #37
3 to 2 Phase
There is an old connection system to convert three phase power to two phase by what is known as a Scott connection. It requires a special transformer and would be very hard to locate.
Find a good electric motor shop and have it would for three phase service.
11-24-2010, 06:24 PM #38
Guys, if he's in Center City, Philadelphia, they still have two-phase, five wire service. Trust me on this.
No comment on the motor being 2 or 3 phase, but Philly still has utility two-phase power. It's the last city in the US so wired.
11-24-2010, 08:05 PM #39
11-24-2010, 09:48 PM #40
im not near philly. the guy was about 20 minutes from me so he was about an hour and 10 minutes away from philly.
all of your suggestions and thoughts seem to be all over the map. ill have to buy a voltmeter and check this motor.
but can someone explain this vfd setup to me more ? what is a VFD .. and dont say a variable frequency drive. im asking what it specifically does.
why is it better then just buying a good 3 phase motor and using that ?
i dont have any other machine, or anything to machine the mounting parts so if i cant buy the parts as a kit or seperatly from stores it isnt happening.