Rotary Phase Converter

[Ralphxj]

I need to get 3phase for my new to me Dake 350sa cold saw. I have researching VFDs and now I'm looking into rotary phase converters. The first thought was to buy something just for the saw, but now I'm thinking about spending alittle more and getting something that can power more equipment in the future. I don't have a mill or lathe and it would be nice to know in the future I already have the power for them. I have a large belt and disc sander that I already converted to 1ph, but if I had the converter already, I would have been set.

I know where I can pickup a brand new 13hp motor for $35 (or less) and it's my understanding a motor this size (over 7.5hp or so) is almost always 3phase? Once I confirm it's 3ph and 220v I'm going to grab it. I see control panels for converters that say they are for either 10hp or 15hp, will either work with a 13hp motor?

It's my understanding that a rotary converter uses very little power when it's not under load? So if I turn it on and let it run when I'm in the shop, but only use the 3phase power for a couple minutes, I'm not actually powering 13hp for the entire time, only really powering the load (say 3.3hp for the cold saw) when it's in use? Just don't want a crazy power bill because I over sized a converter for power that I might need in the future.

 

[callcoy]

I am not an expert when it comes to phase converters, I have one of each type and have split the use between them. I am in my shop by myself so I can only run one piece of equipment at a time. I have set up the rotary unit to run my 16" lathe, my 12" lathe and my mill. My solid state unit powers my metal band saw and my big old drill press. If a friend wants to help out, the only machines I am comfortable letting some else use would be a drill press or a band saw. I would jump at a chance to pickup a 13 hp motor for that kind of money if I needed it. I don't know what kind of control devise you are talking about for the conversion, all that is needed is a rewire to convert. I would search the net for instruction on doing the rewire.

Yes turn it on when you need it, don't leave it running when not needed. good luck with your project.

 

[Ralphxj]

Here is an example of the control panels I'm seeing: https://m.ebay.com/itm/15hp-Cnc-Bal...996258?hash=item361515fbe2:g:bHMAAOSw4CFY1Wuz

That one says 15hp. Will it work with a 13hp motor, or do I get one for a 10hp setup?

 

[Bert_]

13hp is not a standard size I would be a little cautious before buying it, might be a crappy motor. Good used 3 phase motors are cheap. I would think you could make a larger control panel work, probably have to remove some capacitance.

 

[Ralphxj]

13hp is not a standard size I would be a little cautious before buying it, might be a crappy motor. Good used 3 phase motors are cheap. I would think you could make a larger control panel work, probably have to remove some capacitance.

Could be a misprint on the listing, I'll have my guy check it out and get me all the details.

 

[American Locomotive]

That's a 3 phase motor. If it is 13 HP, it might really be a "10KW" metric motor that has a HP rating on it too.

RPC draws little power while not under load. Maybe 1000 watts or so. It's not something you'd want to leave on 24/7, but it's not going to break the bank using it with your equipment.

 

[Ralphxj]

So that motor (if it is a 13hp motor) and the 15hp control panel I posted about would give me 3phase power that would run up to say 7.5hp equipment in the future? For less the a good VFD that I would need for my 3.3hp cold saw?

 

[malibu101]

I have a 10HP 3Ø motor that I use to run my 5HP 3Ø air compressor. 10HP because I got it free.
I'm sure running it even unloaded takes quite a bit of electric. I only run it when I need it for this 1 thing.

I don't have a control panel or anything, I just start it with a small 1Ø motor that I unplug when it's up to speed and I flip the breaker to power the 10HP.

My setup-

 

[Norcal]

The motor looks like a Leeson, so if so it's a domestic brand.

 

[Ralphxj]

The motor looks like a Leeson, so if so it's a domestic brand.

It is a Leeson. Really hoping it's 13hp and not 1/3hp they sometimes don't give good details.

 

[Rusty Bolt]

I've gotten as far as breadboarding a 7.5 HP rotary phase converter. While tuning the capacitance, I've noticed the unloaded converter draws about 200 watts.

 

[Ralphxj]

I've gotten as far as breadboarding a 7.5 HP rotary phase converter. While tuning the capacitance, I've noticed the unloaded converter draws about 200 watts.

It looks like its only a few cents an hour in power consumption in reading online and then looking at the chart on this page: http://www.northamericaphaseconverters.com/shop/category/pro-line-rotary-phase-converters/

 

[Ralphxj]

One last question as I start to plan the electric in the shop. If I want to run a couple of 3 phase drops off of a phase converter, do I just run them straight from the converter, or do I add some kind of breaker or fuse between the converter and the plug?

 

[wyliesdiesels]

I would add a small breaker panel for overcurrent/overload protection.

 

[930dreamer]

13 hp sounds a little odd, make sure it's a 60 hertz motor not 50.

 

[930dreamer]

All my 3 phase equipment has its own fuse/breaker/disconnect.

 

[Norcal]

I would add a small breaker panel for overcurrent/overload protection.

"Small" would be a 12-18 space for a 3Ø loadcenter. As said above, it will be a good way to distribute the RPC output, much easier then hanging a gutter & a bunch of disconnects.

 

[Ralphxj]

All my 3 phase equipment has its own fuse/breaker/disconnect.

Something like this?? https://www.amazon.com/dp/B000VYJRUO/?tag=atomicindus08-20

 

[Ralphxj]

13 hp sounds a little odd, make sure it's a 60 hertz motor not 50.

I'm going to double check everything with week, hopefully it does what I want/need it too.

 

[wyliesdiesels]

"Small" would be a 12-18 space for a 3Ø loadcenter. As said above, it will be a good way to distribute the RPC output, much easier then hanging a gutter & a bunch of disconnects.

Yeah a panel would be easier than cobbling up everything with gutter and disconnects...

 

[Ralphxj]

Yeah a panel would be easier than cobbling up everything with gutter and disconnects...

Gutter and disconnects?

 

[Norcal]

Gutter and disconnects?

Gutter is trade slang for wireway, disconnects = safety switches.

http://www.cooperindustries.com/con...enclosures/enclosures_and_wireway/Wireway.pdf

 

[Ralphxj]

Thanks everyone for all your help. Just found out it's a 1/3hp and not 13hp!

Once I find a good motor to use, I think I have the project figured out.

 

[930dreamer]

What's the hp of your biggest 3 phase machine, a 15 hp should be easy to find cheap on Craigslist etc.

 

[Ralphxj]

What's the hp of your biggest 3 phase machine, a 15 hp should be easy to find cheap on Craigslist etc.

Right now all I have is 3.3hp Dake cold saw but if I'm going to build something, I want it to work for future equipment. What is cheap for a 15hp?

 

[larry_g]

I'm digging into some very foggy memory banks here so bear with me. When I built my RPC 20+ years ago you wanted the motor near the the HP of what you were driving to keep things balanced better. The generated leg should be balanced with capacitors. If the RPC is way over-sized to the load then balancing becomes more difficult and when driving widely varied HP motors the generated leg would go all over the place voltage wise.

So do your research on sizing and balancing before building something way over sized. What tools can you imagine in your shop that are over 5 hp? If you can then you have to consider sizing the wiring supplying the RPC and if your supply from the power company can deliver that much.

lg
no neat sig line

 

[Ralphxj]

I'm digging into some very foggy memory banks here so bear with me. When I built my RPC 20+ years ago you wanted the motor near the the HP of what you were driving to keep things balanced better. The generated leg should be balanced with capacitors. If the RPC is way over-sized to the load then balancing becomes more difficult and when driving widely varied HP motors the generated leg would go all over the place voltage wise.

So do your research on sizing and balancing before building something way over sized. What tools can you imagine in your shop that are over 5 hp? If you can then you have to consider sizing the wiring supplying the RPC and if your supply from the power company can deliver that much.

lg
no neat sig line

I was under the impression that by going bigger, I would be able to run multiple machines at once because of having more capacity? Right now I only habe the 3.3hp saw, but in the future might add a mill or lathe and have a helper in the shop (he is now 4) and need to run 2 machines at once.

Currently only need to run 3.3hp, but was shooting for the ability to run around 5-6hp, combined. So I probably only need a 10hp rotary, but figured if the price wasn't much more, 15hp would be better. Maybe I'm way off base?

 

[Radix2]

I was under the impression that by going bigger, I would be able to run multiple machines at once because of having more capacity? Right now I only habe the 3.3hp saw, but in the future might add a mill or lathe and have a helper in the shop (he is now 4) and need to run 2 machines at once.

Currently only need to run 3.3hp, but was shooting for the ability to run around 5-6hp, combined. So I probably only need a 10hp rotary, but figured if the price wasn't much more, 15hp would be better. Maybe I'm way off base?

I kinda question going in big on a rotary converter these days. VFDs have come down and will keep going down.

Many tools really benefit from variable speed, soft start, etc. - lathes, milling machines, drills, bandsaws - so if it is at all affordable it is much much nicer to run machines that way.

So maybe just get a size to run what you have now and revisit in the future?

 

[larry_g]

I kinda question going in big on a rotary converter these days. VFDs have come down and will keep going down.

Many tools really benefit from variable speed, soft start, etc. - lathes, milling machines, drills, bandsaws - so if it is at all affordable it is much much nicer to run machines that way.

So maybe just get a size to run what you have now and revisit in the future?

I have one RPC and run 8 or more motors off of it. My one big mill has three 3 phase motors on it, the small on has two. That is a lot of investment in VFD's to use as phase converters. I have no argument that there all the advantages of operation you list, but cost is questionable, especially if you have to rework the whole controls system.

Currently only need to run 3.3hp, but was shooting for the ability to run around 5-6hp, combined. So I probably only need a 10hp rotary, but figured if the price wasn't much more, 15hp would be better. Maybe I'm way off base?

If you research a bit more you will find that additional motors downstream of the RPC increase the capacity of the converter. So you do not add all the motors running at one time together to determine the idler size. The idler just has to be able to run the largest motor you have if I remember correctly. Over on the practical machinist site they have a forum just for this subject. http://www.practicalmachinist.com/vb/transformers-phase-converters-and-vfd/

I haven't been in there in years so I'm not sure how good it is anymore.

lg
no neat sig line

 

[Ralphxj]

I kinda question going in big on a rotary converter these days. VFDs have come down and will keep going down.

Many tools really benefit from variable speed, soft start, etc. - lathes, milling machines, drills, bandsaws - so if it is at all affordable it is much much nicer to run machines that way.

So maybe just get a size to run what you have now and revisit in the future?

I started my research thinking a VFD was the way to go. However, to use a VFD I will have to wire it such a way that it doesn't affect a 1ph coolant pump motor, but still controls the main motor and then completely rewire the main control panel through the VFD rather then leaving it as is. I really don't want to mess with all of that if I can help it. When looking at rotary converts I found I could go that route for close to the same price and control more the 1 machine in the future.

At this point I'm not sure there is a right answer, I guess just pick one and go with it.

 

[930dreamer]

If money isn't an object you can go with a phase perfect digital converter.

 

[Ralphxj]

If money isn't an object you can go with a phase perfect digital converter.

I'm looking to keep costs as low as possible, however I don't want to spend a couple hundred and then a few months or years down the road wish I would have spent a little more and made a better choice.

Going the VFD route is going to make operating the saw like a space shuttle launch sequence to run the saw so the rotary converter seems like the better option.

 

[cgrutt]

I had planned to put together an RPC a while back. Have all the parts and a 7.5 HP Baldor Idler motor, just haven't put it together yet. I will say the cost for parts and the idler was significantly more than OP stated not sure where disconnect is. The Baldor motor that I have appears to be significantly larger than the OP's 13 HP, thinking it may be a 3HP? Anyway, here is what I was planning to do...

 

[cgrutt]

BTW, this is the 7.5HP Baldor idler. It's on a full size furniture dolly...

 

[cgrutt]

Thanks everyone for all your help. Just found out it's a 1/3hp and not 13hp!

Once I find a good motor to use, I think I have the project figured out.

Ha, missed that! Makes more sense to me now though...

 

[Ralphxj]

Ha, missed that! Makes more sense to me now though...

Ya I got my hopes up. Was disappointed when I finally got the photo of the motor tag! Now I'm searching for a deal on a 10 or 7.5hp motor

 

[firebirdparts]

On your design, I don't really get Relay 1 (not that it matters). When I built mine, I used a voltage sensing relay that drops out automatically, and it seems like it would have to be connected to another leg for measurement.

On mine the idler is operated by an old cutler-hammer motor starter, and so the starter provides thermal protection to the idler. Your idler is way to big, so barring any unexpected unpleasantness it wouldn't get hot. It might be reasonable to fuse it though.

 

[Ralphxj]

When shopping for a good motor, other then checking that it spins smooth and the bearings are good, how else do I know I found a suitable motor? I'm looking at HGRinc.com and might run up there to shop. How do I know if a $40 motor will work as well as a $120 motor or a $180 one?

 

[Ralphxj]

Would this be a good motor for a converter? https://hgrinc.com/productDetail/Motors/Used-Nord-Motor-/10171431244/

 

[cgrutt]

On your design, I don't really get Relay 1 (not that it matters). When I built mine, I used a voltage sensing relay that drops out automatically, and it seems like it would have to be connected to another leg for measurement.

On mine the idler is operated by an old cutler-hammer motor starter, and so the starter provides thermal protection to the idler. Your idler is way to big, so barring any unexpected unpleasantness it wouldn't get hot. It might be reasonable to fuse it though.

Yeah, other side of coil of the potential relay should be connected to T3 (the blue line in my diagram). My bad. It drives/controls the start capacitor contactor and cuts out the start caps when voltage is sensed on the phantom leg (T3) after idler is running.