My $45 homemade 10 HP phase converter is WORKING!!!

Your furnas contactor is the only relay you need. You use the extra pole as the hold-in contact.

All you need are the two pushbuttons, which you could get at the same surplus place you got the other stuff. They will be in a single housing, one will be black and momentary NO, labeled "on" and the other will be red, momentary NC and be labled "off."

The most you might need would be a separate 120 volt ckt to run the contactor. Be sure to *fuse* the smaller control ckt with a fuse that is appropriate to the control wiring. This will be a couple of amps or so.

Jim

Reply to
jim rozen
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Oh, yes, that's right. How stupid of me not to think of that. I will try to dig for a start button and stop button. I think that that's all I need.

Well, I can use a separate neutral just for control purposes.

Anyway, is this start/stop switch just what I need?

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thanks

i
Reply to
Ignoramus9394

I agree, that's the way I will do it. Is this switch going to work for me?

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i

Reply to
Ignoramus9394

That's the one I would use.

Jim

Reply to
jim rozen

It looks like you're only using 1 contactor to switch the incoming lines, right? If that's the case, your converter will be imbalanced because, in order to start the RPC motor quickly, you have a large amount of capacitance permanently connected between L1 and L3. The correct way to wire it is using a start contactor to switch a big capacitor between L1 and L3 and have permanently connected smaller capacitors between L1 and L3 and also between L2 and L3 to balance the converter. I also agree with the other posters, use a No Volts Release circuit using a start and stop button and the spare or auxiliary contact on the main contactor to hold it in. Well done on getting the parts so cheap, those caps must be worth $40 a piece. Martin

Reply to
Martin Whybrow

Jeff supplies an excellent example of a safety interlock designed to prevent serious injury, because a person can't always predict all the possibilities involved when a machine stops unexpectedly.

Almost everything in life is a cost issue, but the saw manufacturer knew that preventable injuries would end up costing them.

Having start/stop controls within easy reach of the machine operator, locating the electrical service disconnect within sight of the machine, and more than one level of protection for the equipment, are all considered to be required protections in a working environment. They should also be sensible for the DIY home shop worker to utilize in their machine power circuits.

Having the contactor drop out for a loss of power condition isn't especially complicated, and not expensive to implement.

Examples of start/stop circuits for magnetic starters can be found here.. see Simple Magnetic Starter Deluxe Magnetic Starter

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Wiring diagrams for commercial RPCs can probably be found at most of the manufacturers' websites, as well as here at the ARCO site
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WB .............

Reply to
Wild Bill

This just means that you've wired it to a standard switch. Normally for motor use the contactor is switched with two push button switches. One is normally open and the other is normally closed. The normally closed switch is wired to the output of the contactor in such a way that when the contactor is closed it provides itself the coil voltage. When the normally closed switch is pressed this breaks the coil voltage allowing it to shut off. The normally open switch is wired to the input line and then to the coil. This allows pressing that button to start the coil which is then held by the above switch.

The problem here is that IIRC you've got a 120v coil on your contactor. This makes it difficult to wire this type of switch up. The only way I can think of right now would require two transformer to bring the 220v down to 120v.

Reply to
Wayne Cook

| >>I see. I plan to install a regular household light switch to control | >>the contactor. UP means run, DOWN means stop. I will have two | >>electrical boxes on the outside of my RPC: one for incoming single | >>phase power and the switch, another for outgoing power. I may also | >>install a Square D disconnect on the outgoing side of the | >>converter. I already bought that disconnect used. | >

| > You can use your furnas contactor as a drop-out device. | > You wire it to hold in, using the third contact. | | Oh, yes, that's right. How stupid of me not to think of that. I will | try to dig for a start button and stop button. I think that that's all | I need. | | > The other two contacts carry the incoming 240 volt lines | > to the motor. | >

| > This way a control circuit (which really should be derived from | > the same incoming 240 volt lines via a 240:120 transformer) | > with two pushbuttons can run the thing, and the buttons don't | > carry the load currents. | | Well, I can use a separate neutral just for control purposes. | | Anyway, is this start/stop switch just what I need? | |

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| | thanks | | i

That will work, but if you intend to use it, you want to learn how to work with basic control wiring, as start-stop stations are usually expected to be set up with a holding contact. What that means is when the start button is pushed, the starter engages, and an auxiliary contact then bypasses the start switch, holding it on when you let the start button go. The stop button is wired in series with the holding circuit, so that when you push the stop button the circuit "falls out" completely. Personally, I'd recommend a stop button of the mushroom style as a better safety function. Anyone can slap the stop button and it shuts down. There's a specific minimum distance that is required between the stop button and the machinery, and often there will be more than one stop button, which complicates the wiring dramatically. I like the simple mushroom with a push pull. When pushed in, the equipment is unpowered, and when you pull it back out (or twist it to the left to release it,) it can operate again. Your call as to where you sit safety wise and all that, since it's obviously not an industrial application that has to conform to all the same rules. IIRC, OSHA or some other agency has changed the rules about safety stops, leaving a lot of old hardware out there.

I'm not sure I read it all correctly, but the mention of a dropout confused me. A dropout kills specified circuitry when a particular phase drops out, low voltage exists on any leg, or a few other conditions exist. You can do just that by simply changing the contactor coil to a 240V coil and wiring as such. If you lose the leg that isn't providing control power things will be unsafe although the RPC won't be running, but if the coil is across both legs, then there's the inherent safety.

I'm not trying to get you to spend more money on a project that you are obviously proud of. I commend you for whipping it up for so cheap, because I'd be trying to do it even cheaper if I could. However, seeing as how you value the lives of your children, and I assume your own, safety to me is more of an issue at home than at work in this respect. At work I understand and properly deal with the inherent hazards that I know exist, as I've been trained to do. I can't expect SWMBO and my kids to understand, nor do I expect them to instantly know what button to push when they're panicking, as the victim could be you. The simpler the shutdown process the better. As long as they know that there is one simple button that can be operated with an elbow or hand the better. Something like this comes to mind:

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Not necessarily the source you want (although inexpensive) is automationdirect.com and if you look at item E22JPLB2B you'll get the idea.

If you want, I will revisit your schematic and see if I can help you make your control both wiring simple and safer for all of you, although I'm sure there's folks here more experienced than I in the matter. The best part is that if you think surplus three phase motors are cheap, you should see all the gobs of control devices that get tossed regularly! It's cheaper than trying to salvage them, so usually they hit the trashpile. Your surplus supplier might have a control box or twenty that has the hardware you can salvage. Lots of folks think they can save the control boxes, too, but that's even more specialized than the contents, unless it's more standard or hasn't been punched out too heavily.

Again, I want to add how much what you've done on a shoestring for many things has impressed more than just me, I think it impresses a lot of us, and the fact that you are willing to ask for help and take this overload of information in and make good use of it without taking too many of us personally. I just wish you were my neighbor, I wouldn't have to buy or build all this expensive stuff myself!

Reply to
carl mciver

Or, he can run it off a separate 120 volt ckt. Or use a

240:120 volt control transformer.

Jim

Reply to
jim rozen

Motor controller and you'd better find one used. New ones are big bucks in that size.

It's possible to use the contactor you have now with the addition of a few things to make a motor controller. I'd forgotten the fact that you have a 3 pole contactor and you're only controlling the single phase input so you can use that contactor with a pair of push button momentary switches (one normally closed and the other normally open). I happen to know that McMaster Carr sells a switch like this already in a case for around $40 (we just got through putting one like it on a friends new to him Logan lathe which is being powered by a VFD). But these kind of push button start/stop switches are used on a lot of equipment and should be easy to find if you look.

The tricky part is the overload protection. There are electronic overload sensors out there that can be added to a setup like this. However I'm not sure that I've ever seen any that aren't 3 phase. You won't be able to use the 3 phase version since one of the things they check for is all 3 phases loaded evenly. Drop one phase and they kick out. If you can find a single phase version of these then you're set. I have my doubts you'll ever find one used since they're a relatively recent innovation in motor controls. I've not seen to many coming out of used equipment yet.

Reply to
Wayne Cook

Rules that work well for small folks. There's no gray area, there's only a single, bright line so it's easy to tell if you are complying, or not.

For example, my household has a bright line rule that there's 8 hours between the bottle and any throttle. This means no drinking if you have to drive home. None.

Or, my daughter wears safety glasses at all times when in a shop or lab. No question about the activity going on, it's an absolute.

With canoes, the rules are no standing up in the boat, and if the boat sinks, stay with the boat.

With guns, the rule is, all guns are always loaded, all the time, and are treated as such - ie never point a loaded gun at anything you do not want to destroy.

When kids are small it makes it easy - 'stay in the yard' or 'you have to hold my hand in parking lots' or 'vehicles are not toys' - for them to understand how to behave correctly.

Jim

Reply to
jim rozen

I think that I have almost everything that I need, here at home. I looked into my parts pile and found the following:

  1. Two pushbuton switches, one NO/NC (depending on how it it wired), one NO.
  2. A large terminal block.

  1. I have a 30A heavy duty Square D switch that I will use for the output side of the RPC. ( at the junkyard)

The way it will work is as follows.

- Incoming wires will come in through one electrical box, mounted on outside. That box will be covered by a solid cover with two 5/8" holes. Pushbutton switches will be mounted in these holes. That will be hte input side.

- Inside, I will have a furnas definite purpose 50A switch, wired like Jim and others say, to be actuated by the ON switch and disengaged by the OFF switch.

- The motor will be wired to 2 capacitors, as before.

- Three legs of 3 phase will be going into a Square D disconnect, where I would be able to disconnect output of my RPC independent of input.

- Then, wires would go into another electrical box for output. That box will also have a solid coverand a terminal block mounted inside. To add a device, I would open the cover and plug the wires into the terminals.

It will look like this

Incoming BIG Box / w ASS buttons SQUARE D Output DISCONNECT Box SWITCH terminal

i
Reply to
Ignoramus9394

Why, I will just bring in a neutral. Thanks for the advice, I will actually follow it.

i
Reply to
Ignoramus9394

I do not see what the big deal is, I will simply bring in 4 wires, 2 hots, one neutral, and one ground. Hot to neutral will be 120 V.

i
Reply to
Ignoramus9394

Carl, I am quite touched by your post. I feel that I do not deserve the compliments. As regards to stop and start switches, I have two pushbutton switches, a NO and NC that I can use. But maybe it is better to spend $13 for a surpluscenter switch, considering your valid point regarding wife and children who should be able to stop the RPC.

I am not really poor, I just like to do things on the cheap because that is a challenge. Anyone can buy an RPC on ebay. Building it for 10 times less and in a more user friendly way, is an interesting challenge. Plus, I really like digging in trash piles and messing around with stuff.

Electrical designs and control issues (electrical, not psychological) remind me of computer programming and logic.

i

Reply to
Ignoramus9394

Thanks Wayne.

i
Reply to
Ignoramus9394

Is there any way that I can rig up a phase converter such as shown below, and attach another power source (read gas or diesel engine) to the actual rotor, and come out with quality 3 phase eclectic power of 60 Hz?

Reply to
The Tagge's

that would be called a "generator". As far as I know, induction motors are not suitable as generating ends. In a rotary phase converter, the third leg is produced thanks to the magnetic field made by the utility supplied hot leg.

i

Reply to
Ignoramus9394

yes.

the voltages between lines were 255V (utility power), 240V, and 259 V (IIRC). That's acceptable.

I will follow your advice regarding start and stop button. The guy selling these caps to me did not know what they were. That could explain things.

i
Reply to
Ignoramus9394

Actually it is possible with some motors. It may require a short DC pulse to start it off. My understanding is that some motors work better than others in this application. But if you stay within the motors rating it will work (if the motor will generate at all). One key feature of this type of generator is that if you exceed the motors rating it will simply stop generating.

I recently scrapped a welder/generator with this same setup in it. They did have some extra windings wound onto the ends of the field windings to help it start up and stabilize it but otherwise it was just a 3 phase motor with a engine hooked to it. The welder was a Thermadyne but it was obvious from the components in it that it was made in Italy. In this case the touted cuts out if shorted rule seemed to not work and there was a short in the windings caused by a short in some internal leads of the welder. .

Reply to
Wayne Cook

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