What's new
What's new

motor only hums, wiring help

Steve@610Euro

Plastic
Joined
Oct 6, 2010
Location
PA, USA
i bought this mill off of a gunsmith. he really had no idea what to do with it and didnt know what was wrong with it. while i was there taking it apart to transport it to my shop, found water all in the machine. the rubber line the electrical wires were in was filled with water, the spindle housing was filled with water, the base of the machine was also filled with water. after seeing all this he decides to admit the whole building and the machine were in a bad flood. :angry: the machine was cheap so i wasnt too worried about it.

the machine is now in my shop back together. spindle spins free, no issues there, new belt and replaced a few other pieces that were broken which the guy never told me about.

my issue now is, when turned on the motor only hums. it doesnt spin at all. you can spin the motor freely by hand so its not locked up.

here is how it is currently wired through a 250V outlet. on the fuse box end thats 2 - 50 A posetive fuses. motor wires have metal labels from 1-9, all the wires are black.

Picture579.jpg


this is the cover for the motor.

Picture570.jpg


Picture575.jpg


any help would be appreciated. id really like to get this thing up and running as soon as possible.
 
That's a two-phase motor. It won't run on single-phase AC.

You'll either need to build an RPC with two-phase output, or replace the motor.

Not sure how you would accomplish the first option.

Maybe Peter can help.

- Leigh
 
whats an rpc ?

what motor should i be looking for ?

according to the guy i bought it from it worked the way they had it wired, i had to remove the wiring from the place and how i set it up is how it was.
 
It's not a 3-phase motor.

The motor is doing what is commonly called "single-phasing" due to the fact that you are applying single phase power to a three phase motor...
It's a 2-phase motor. The nameplate says two-phase in two different places.

Of course the actual motor installed in the machine may not match the nameplate. :eek: :nutter:

- Leigh
 
whats an rpc ?
RPC = Rotary Phase Converter
It's a motor-generator that produces the required output voltage and phase(s).

what motor should i be looking for ?
A 1725 rpm 1 hp motor on a 4570 frame would be a drop-in. The frame number identifies the dimensions and mounting of the motor.

I don't know if that frame is still in production. My Bridgeport motor has the same 4570 designation, but it's 220/440 three-phase.

according to the guy i bought it from it worked the way they had it wired, i had to remove the wiring from the place and how i set it up is how it was.
He may have had two-phase power in the shop, or an RPC, or some other means of sourcing the required two-phase voltage.

I believe two-phase power is still available in some areas.

It's also possible that they wired it to two legs of a three-phase service. I have no idea if that would work, but perhaps it would.

I hope Peter jumps in here. He's far more knowledgeable on this subject than I.

- Leigh
 
Maybe I'm just confused, but isn't 220 volt 2 phase already? Each 110 volt leg is a single phase, with 110 volts from each phase to ground, and 220 volts from one phase to the other.
 
Did he follow the wiring diagram correctly ?

It appears that Steve connected the wiring like a standard three phase motor but the "2 PHASE" :o diagram shows different connections than he shows in his diagram

1-7, 2-8, 3-5, 4-6 using eight motor leads shown on the plate. He has it set up like low voltage three phase 1-7, 2-8, 3-9, 4-5-6 when the plate does not show a number 9 motor lead at all. :confused:

I wonder could the motor have been rewound at some time to a 3 phase configuration or would the number of poles etc and the original design make that modification impossible?
 
...isn't 220 volt 2 phase already? Each 110 volt leg is a single phase, with 110 volts from each phase to ground, and 220 volts from one phase to the other.
Nope. It's single-phase.

If you use either hot leg as a reference, the phase of neutral and the other hot leg will be the same.

- Leigh
 
the guy didnt have any phase converter, it was all wired exactly like i have it. i had to follow the wiring to the fuse box to kill the power so i could remove it. the wires lead directly to a standard fuse box with 2 50A fuses and the other 2 wires were ground. i didnt change or remove any of the wires in the head, to the switch . i simply wired the 4 wires leaving the machine to the 4 wires from the fuse box in the same patten as was in the original location. it could all be wrong. the guy wasnt real good at telling the truth up front.

the cover on the motor had me confused, considering it only shows 8 leads and there is in fact 9. but like i said, i havnt changed any of that setup, thats all how it was.

anyone know a cheap source for a good phase converter ? id rather go that route considering im picking up a south bend lathe soon that is also 3 phase.
 
more questions while on the subject:

why a rotary phase converter and not a static one ?

to power this motor what hp converter should i be looking for ?

can i attach a plug to the output on the phase converter to allow me to use it on both machines, or do i have to buy a seperate converter for each machine ?
 
the guy didnt have any phase converter, it was all wired exactly like i have it. i had to follow the wiring to the fuse box to kill the power so i could remove it. the wires lead directly to a standard fuse box with 2 50A fuses and the other 2 wires were ground. i didnt change or remove any of the wires in the head, to the switch . i simply wired the 4 wires leaving the machine to the 4 wires from the fuse box in the same patten as was in the original location. it could all be wrong. the guy wasnt real good at telling the truth up front.
Two fuses imply a two-phase service. A three-phase service would have three fuses.

The two unfused wires could be neutral and safety ground.

- Leigh
 
why a rotary phase converter and not a static one ?
A static phase converter is no such thing. It simply provides a phase-shifted voltage on the third leg of a three-phase service for the purpose of starting the motor. As soon as the motor is running, that leg is disconnected and the motor continues to run on two wires connected to the single-phase service.

to power this motor what hp converter should i be looking for ?
The solution to your problem is rather complex and requires further analysis. My recommendation would be to replace the motor. Then you would need a converter rated for the motor horsepower.

can i attach a plug to the output on the phase converter to allow me to use it on both machines, or do i have to buy a seperate converter for each machine ?
It's possible to do so if both motors are the same voltage and horsepower and both are three-phase. This obviously requires replacing your existing two-phase motor.

- Leigh
 
his fuses were in a fuse box exactly like mine, wired in the exact same manor. ther is no difference between the 2 setups. but enough about his setup vs mine.

replacing the motor and then buying a phase converter is looking to cost about another 800-1200 depending on which motor/converter i went with. thats as much as i paid for the whole machine. not willing to put that much into this thing.
 
Based on your wiring diagram showing how it was wired, this motor has been rewired for 3 phase power, the wiring you have is typical for a 3phase system wired for low voltage. since you are only supply single phase to it then it would only hum.

You can verify this with a ohm meter disconect power from moter and measure the resistance from each leg to each other i.e. red-black, red-bare, black-bare all should read within about 1/2 ohm or so from each other
you could also disconect all wire and useing the img below verify the setup
see image below look at the WYE configuration this is most likely what you have

fig21.gif


you could go with a RPC or a Veriable frequency drive to power it. I use a VFD for my lathe and will put one on my mill soon.

Important GET RID of the bare wire this is an ELECTRICUTION hazard since this wire will be hot.
 
The more I think about it, you may have a three-phase motor. The fact that you have nine wires rather than eight argues strongly for this configuration.

If that's the case, then usmachine's observation that you're motor is "single-phasing" would be correct, and the seller's assertion that it was working would not be correct.

Here's a pic of the connection diagram from my three-phase Bridgeport motor:
BridgeportMotorWiringS.jpg


If this is true, I would suggest a VFD to generate your three-phase power. You can get one rated for single-phase in driving a 1 hp three-phase motor pretty cheaply.

It's important to confirm that it's rated for single-phase input. A VFD rated for only three-phase in would need to be up-sized by a factor of two to operate on single phase, i.e. you'd need a VFD rated 2 hp for your 1 hp motor.

You could use a static converter, but in this small size it would cost about as much as a VFD, and you would not have the speed control nor the full power available with the VFD.

- Leigh
 
Last edited:
A check of the basics: If the person you bought this from just had 2 fuses in the box he didn't have 3 phase power hooked up to this unit. When you hook up to your service power did you use a double breaker and have you verified that you are getting 220 volts at the outlet between the two hot legs (red/black?)? It is possible to tap into two 110 sources that are the same phase (like with a double half-height breaker which people use if the box is full). You will get 110 volts to ground/neutral from each leg, but zero volts from one leg to the other. If you are correctly wired, you should see 110 volts from each leg to ground, and 220 volts from one leg to the other.
 

ill try and figure this out soon.

i have to rewire this all to another location in the shop so ill change out the open wire.

can you guys reccomend a good vfd and a good phase converter ? you guys seem to throw them out there but they seem to have greatly varying models and prices, from $70 to way over $1000.

i deal with cars all day, this home electrician work is not my strong point.
 








 
Back
Top