3-Phase/ Phase Converter?

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Old 01-09-11, 05:29 PM
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3-Phase/ Phase Converter?

Has anyone ever used a phase converter to create the 3rd leg for 220/3-phase? I just bought a used Phase-O-Matic with a 7.5hp motor and I'm having trouble getting it hooked up to my equipment. I will be running a 1.5hp mill and a 3hp lathe, but prob not at the same time. I currently have it grounded directly to the motor from the 100 amp box in my shop, is this ok or do I need to drive a ground rod?
The motor to the phase converter works just fine, but when I try to start the lathe for example, the converter will shake and make a loud noise.. Common sense tells me this isn't a good noise, so I have been leery about doing anything further. My next step is to start swithching wires around until I get good results, any input before I do this will be greatly appreciated. Thanks
 
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Old 01-09-11, 05:47 PM
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I think I'd start by checking voltage output of the converter, phase to phase, and be assured you have the proper voltage on all phases. For testing purposes, it might be better to test it with the lower HP machine. If you still have a problem you have to start asking why the previous owner is no longer using it.
 
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Old 01-09-11, 07:00 PM
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Do you have the phase rotation order hooked up right at the lathe? The vibration could be mechanical from the motor turning the wrong way.
 
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Old 01-10-11, 10:03 PM
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Making progress

Ok, I've got the mill wired up and it seems to run just fine and I can start it with out the converter making any noise, leading me to believe the problem exists with the lathe itself or the wiring.??
I'm assuming that the rotation is correct because the lathe spins the right way when I start it, at least its the same as one I've used before that has foreward and reverse. I got it to run, but it won't run for more than a couple minutes and shuts down. The converter still vibrates though when I start it up. There are two thermal overloads in the electrical box mounted on the lathe that got really hot when it shut down. They look like small springs mounted to a ceramic body, and there not melted. Are they still good or should I replace them?
I will also check the voltage output on all three strands and let you know what I find out. Should the voltage being created by the phase converter be the same as the two coming from the main box?
 
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Old 01-11-11, 06:23 PM
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I will also check the voltage output on all three strands and let you know what I find out. Should the voltage being created by the phase converter be the same as the two coming from the main box?
Your 3-phase motor doesn't know you have a phase converter, it's just looking for 240 volts across all phases.
 
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Old 01-20-11, 05:46 PM
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Lathe Thermal Overloads

Does anyone know about Thermal Overloads, or "Heaters" for a Furnas Magnetic Starter? They're like little springs with a ceramic shield. Kinda look like a big fuse to me. Anyway, my lathe would run for a minute or two and shut off, and I was told to replace them and it would work. After replacing them, as soon as I engaged the gears to the lathe the Thermal Overloads got hot so I shut it off. Are they supposed to get hot? They cost $67 to replace, so I'm a little hesitant.
 
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Old 01-20-11, 06:00 PM
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Sounds like they had the wrong amp rating. Did you match the amp rating to the amps of your motor.
 
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Old 01-20-11, 07:55 PM
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Sizing heater coils isn't difficult. Check this link, it's pretty good on the subject and simple. Is the $67 for all 3 heaters? That seems high to me.

General Electric Heater Coil Selection Chart
 
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Old 01-21-11, 10:32 AM
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Originally Posted by Phoenix23 View Post
They're like little springs with a ceramic shield. Kinda look like a big fuse to me.
They work similar to a fuse in that their purpose is to prevent your motor from melting down. I think your heaters may be the wrong size for the motor, but it could be related to your phase converter too. What is the supply voltage and what is the voltage rating for your lathe motor?
 
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Old 02-07-11, 11:17 AM
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Sorry I haven't replied, I live in Michigan and I do snow removal in the winter and if you watch the weather you know we've been busy!
The phase converter I'm using is the same one that ran the equipment from the guy that I bought it from. Everything worked when I bought it. The thermal overloads that I purchased are exactly the same as the ones that went bad. In fact, when I put the new ones in, the lathe started better than ever, they just got hot, and I just got scared. If I knew that they were supposed to get a little hot, then I would try and run it again. And yes, I bought two of them for $67! I'll definitely shop around next time.
 
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Old 02-07-11, 04:19 PM
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Did you check the voltage as yet. Just wondering if you are on one of those new power sources, Which is not 240 , it is 208. In our old electric service 3 phase was 120-120 wild leg 208. In the new service 3 phase is 120-120-120, but when you check across you get 208 volts. All my old rooftop equipment had to be worked on. I had to install new transformer on all those units. Is your phaser putting out 170 or more Volts? Paul
 
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Old 02-07-11, 07:29 PM
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Method Number 2 Isolation Switch Installation
Phase-A-Matic Static Phase Converter Installation

Stroll down and find wiring for method No. 2 In the wiring diagram where it says
single pole switch , I use a a spring loaded switch so you can hold the switch until
the 7.5 motor gets up to speed then release it and then you are ready to run your
3.5 motor. Paul
 

Last edited by paul52446m; 02-07-11 at 07:37 PM. Reason: adding a note
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Old 02-09-11, 11:02 PM
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Originally Posted by Phoenix23 View Post
I will also check the voltage output on all three strands and let you know what I find out. Should the voltage being created by the phase converter be the same as the two coming from the main box?
This is what frightens me. If you are creating three-phase power, then the only conductor you should be using from the main box is the ground (and maybe neutral). If you are using the two phases from the box, and trying to get a third conductor from your phase converter, you are doing it wrong.

Easy way to test this: Check the voltage between all three of the hot "3-phase" leads. A -> B, B-> C, and C -> A. If they are not all within a couple volts of each other, you have done something fundamentally wrong.

The problem is that standard residential boxes are single phase, center tap. This means the whole building is fed off of a single transformer coil at the pole. The two hot leads are 180 degrees opposite in polarity as they are opposite ends of that single coil. 3-phase requires three coils, that are 120 degrees separated in polarity. So to convert 1-phase residential power to 3-phase requires creating an entirely new set of hots. You can't create the third wire and use two existing ones, that isn't three phase power.
 
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Old 02-10-11, 01:06 AM
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Originally Posted by paul52446m View Post
Method Number 2 Isolation Switch Installation
Phase-A-Matic Static Phase Converter Installation

Stroll down and find wiring for method No. 2 In the wiring diagram where it says
single pole switch , I use a a spring loaded switch so you can hold the switch until
the 7.5 motor gets up to speed then release it and then you are ready to run your
3.5 motor. Paul
That is for a static converter. OP has a rotary, which is basically already the exact same thing as that diagram. A rotary uses the static converter to start the idler motor, which then generates the third phase.
Originally Posted by mukansamonkey View Post
This is what frightens me. If you are creating three-phase power, then the only conductor you should be using from the main box is the ground (and maybe neutral). If you are using the two phases from the box, and trying to get a third conductor from your phase converter, you are doing it wrong.

The problem is that standard residential boxes are single phase, center tap. This means the whole building is fed off of a single transformer coil at the pole. The two hot leads are 180 degrees opposite in polarity as they are opposite ends of that single coil. 3-phase requires three coils, that are 120 degrees separated in polarity. So to convert 1-phase residential power to 3-phase requires creating an entirely new set of hots. You can't create the third wire and use two existing ones, that isn't three phase power.
Not really. In fact, that is exactly how they are wired up. They only have 3 terminals (plus ground). It uses the two hots as phase A and C (which also power the motor), and the converter creates phase B. You can actually make a phase converter out of basically ANY 3 phase motor. The 'store bought' phase converters are just a shaftless 3 phase motor rigged to be able to start on single phase, with some capacitors to help balance the output.

 

Last edited by JerseyMatt; 02-10-11 at 01:30 AM.
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Old 02-10-11, 11:18 AM
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Originally Posted by JerseyMatt View Post
That is for a static converter. OP has a rotary, which is basically already the exact same thing as that diagram. A rotary uses the static converter to start the idler motor, which then generates the third phase.


Not really. In fact, that is exactly how they are wired up. They only have 3 terminals (plus ground). It uses the two hots as phase A and C (which also power the motor), and the converter creates phase B. You can actually make a phase converter out of basically ANY 3 phase motor. The 'store bought' phase converters are just a shaftless 3 phase motor rigged to be able to start on single phase, with some capacitors to help balance the output.

He said he has a phase -o-ma tic converter and a 7.5 3 phase motor
to make the third leg for three phase, so if you go to this site and go down to method no.2 it shows a phaser to start the 3 phase 7.5 motor which he gets his wild 3rd leg That wild leg will be at least 190 volts. I have done this two times for some friends. What i did instead of using a phaser to start the 7.5 motor, i used a 120volt 3/4 HP used motor and run a belt to the 7.5 motor. I used a spring switch on the 3/4 motor. Turn on the 3/4 motor ans as soon as the 7.5 motor is up to speed turn on 240 switch to 7.5 motor. We ran a mill and a lathe at the same time.
Phase-A-Matic Static Phase Converter Installation
Look at method two, that is what he said he had paul
 
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Old 02-10-11, 11:45 AM
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I just read his first post again . He never did say if he has a Rotary converter or a static with a separate idler motor. Did he? Paul
 
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Old 02-10-11, 01:42 PM
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Alright, OP will need to clarify, but I read it as he has a 7.5hp rotary. He says he has a "phase-o-matic WITH a 7.5hp motor", and he is "having trouble getting IT to work with his equipment", implying it is all one unit. He also mentions when he starts the lathe, "the converter will shake".

Like I said, if this is in fact a rotary, it is already the exact same thing as the static converter plus idler.
 
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