Does anyone know if i can reuse this overload relay on my single phase conversion? Im using a l14-30 plug which is 220v single phase plus a neutral for 110. Can i run each 220 line and the one neutral through it to still have some overload protection? I attempted to find info on this online but cant find any because of its age.
Using a 3 phase overload relay on single phase
- Thread starter 05plsrt4
- Start date
Based on your second picture, the contactor can handle 9.5hp at 220V 3ph. This is approximately equivalent to 5hp 1ph.
So yes, you can use the contactor in a single phase cuirciut as long as the load is not larger that about 5hp equivalent.
From the pictures, this contactor most likely has load resistors on each phase leg. If you open the perforated cover, you should be able to see them. Depending on their rating, the contactor may trip at lower than the max 5hp 1ph if you use it for that. You may need to find differently rated protective resistors.
So yes, you can use the contactor in a single phase cuirciut as long as the load is not larger that about 5hp equivalent.
From the pictures, this contactor most likely has load resistors on each phase leg. If you open the perforated cover, you should be able to see them. Depending on their rating, the contactor may trip at lower than the max 5hp 1ph if you use it for that. You may need to find differently rated protective resistors.
It depends - see above; it may trip early.
Chipper5783
Well-Known Member
Yes, you just need to respect the current. The overload device senses the current in that leg (for example in a 3 phase motor starter). The three overload heaters effect small control contacts that are in series, if one opens then the motor stater coil is going to drop out. If one leg draws excessive amps, then that control contact will open - the fact that the heater beside it has no current at all makes no matter.
I suggest only doing the hot conductors, not the neutral. The main load is across the 240v, so the neutral is not going to see much current (perhaps a light bulb or some control power).
Maybe one of the electrical wizards here can chime in? I don’t recall ever see protection on the neutral branch of a circuit.
I suggest only doing the hot conductors, not the neutral. The main load is across the 240v, so the neutral is not going to see much current (perhaps a light bulb or some control power).
Maybe one of the electrical wizards here can chime in? I don’t recall ever see protection on the neutral branch of a circuit.
A friend of mine made a rotary phase converter for his 5HP lathe using a 10HP 3 phase motor to help generate the third leg. As I recall he had issues because of the current imbalance between the 3 legs and his 3 phase breaker on the lathe would periodically trip.
It's such a long time ago and I don't remember much else about that. Just something to think about.
It's such a long time ago and I don't remember much else about that. Just something to think about.
The trouble is that there are contactors that will trip if the 3 phase circuit is not balanced - they act a little like a ground fault indicator. Others may know more than me, but I would not be able to tell you how yours works without the technical data sheet and perhaps not without taking it apart.
You can certainly just test it to find out. But if I were you, I wouldn't fuss over it. I'd just go get a single phase contactor and be done with it. Besides, someday you or your children will be back in there trying to figure out what you did. It's easier all the way around to just do it right.
I agree with Susquatch - using this is more trouble than it is is worth.
If you do use it, don't connect the neutral. Your best result will probably come from connecting _ONE_ hot line only, but unless you have something specific in mind, why not rely on the breaker?
If you do use it, don't connect the neutral. Your best result will probably come from connecting _ONE_ hot line only, but unless you have something specific in mind, why not rely on the breaker?
Looks to me like someone let a newly graduated electrical engineer loose on that machine with no budget constraints!
Do you really need to keep all that?
If it were mine, I'd be thinking about gutting it and simplifying it.
What is this machine? Or did I miss that?
I'd reuse what I could too. But I'd never convert it to single phase. In fact, if it were single phase, converting it to 3 phase would be at the very top of my priority list.
So tell us why you want single phase. We will all do our best to talk you out of it.
I made a plan. Priced it out three ways. Rotary phase converter and transformer, vfd’s and new motors, or single phase. All prices were about the same.
I chose single phase because i wanted it all the electronic, etc inside the mill. I dont have alot of space. I have 240v in the garage.
You can do you best to talk me out of it, but ive already purchased all 3 motors and all the bits and peices to convert it. Minus the main power switch. Trying to see if I can reuse it.
I chose single phase because i wanted it all the electronic, etc inside the mill. I dont have alot of space. I have 240v in the garage.
You can do you best to talk me out of it, but ive already purchased all 3 motors and all the bits and peices to convert it. Minus the main power switch. Trying to see if I can reuse it.
Chipper5783
Well-Known Member
One reason to stay with the 3 phase via a converter and X-mer is that it is an easy solution. When I got my first lathe, I hard wired the converter to a breaker and the lathe straight to the converter (ran that way for about 5 years). When I got a 2nd, 3rd 3 phase machine, then I got a 3P panel and set up a little distribution system. With a phase converter you don’t need to touch the original electrics (Schaublin has a good name, they probably did a good job of it - quality kit, well selected, competent assembly). Obviously you can mod it out any way you like - but with a phase converter you would be running in about an hour, and everything will work as per original. If you choose to make a rotary converter, it will take longer but can be very inexpensive - (they look pretty simple, many plans online). Used X-mers are pretty common (my 240/575 6.5kVa box was $100) - still a very easy solution. And then when you get more machines, they will be very easy to connect.
Once you buy expensive parts it's tough to change course. At least you considered the options. Most people just choose what they know how to do already and don't consider anything else.
No sense trying to change your mind now. Besides, the direction you have chosen will work.
Schaublin makes a very nice machine.