# 25hp 3pahse conveter with load center



## Karl_T (Oct 17, 2014)

*25hp 3phase converter with load center*

*Reposted from another forum - summer 2014 project*


My son is building a new shop. He's one hell of a machinist and CNC programmer, but challenged with electricity. So, I'm building a deluxe converter setup he won't outgrow.

For an overview, this will be a two motor system with a 5hp used to start a 20 hp phase converter motor. The 20 could  easily be larger if more power is ever needed. The system will feed a 3 phase load center panel so all he has to do is add a breaker and wiring any time another machine is added.

Couple design details, the system uses no start capacitors, only run caps. Turns out the amount of capacitance needed to start a 5hp. is almost exactly what is needed to balance voltages on a 25 hp running unit. He's also adding voltmeters to monitor voltages and plenty of spare/extra caps to quickly change things if one leg runs too high/low on voltage.

The deal we struck - he does all the heavy duty power wiring. I'll come in and do the control wiring and system tuning.

I gave him this long message for working notes:




Wiring cookbook. Print this out and check off everything twice.

A: MAIN TO 3 PHASE
Two 100 amp wires from 100 amp fuse in main panel to top of 3 phase load center
Suggest red tape on L1 leg and blue on L3

Neutral from Main to 3phase neutral lugs
B: 3 PHASE TO CONVERTER PANEL
 Find correct breaker size for a  25 motor. (probably  40)  Run three correct size wire to top of 25 contactor.
(I always do Red tape on L1, on  Yellow L2 “wild”, blue on L3. Note: many installs put the wild on L3, Decide now which way to go forever. Do this on every wire both ends ALLWAYS on all your 3 phase power wiring) Bad things will happen if you ever cross these legs

Also do same for 5 hp. contactor.  Pretty sure you want 20 amp and #12 wire here. if you want voltmeters, go from top of 5 hp contactor to the meters.  Detail, wires going to a door should all go to same location beside the hinge, the run parallel to the hinge for several inches and then on to the door.

Neutral  from 3 phase lugs to a small terminal strip in converter panel. Use white #12 wire.

You’ll also run a power wire from a small  1 phase breaker. See logic wiring.

C: PANEL TO MOTORS
Wires from bottom of contactors to each motor. Check you have the right size contactor heaters (overloads). Also look at  attached for motor lead wiring. ID your legs with tape.

D: CAPACITORS
Two #12 wires from L1  5hp motor contact to left side of top and bottom caps in column one. Jumper wires between each cap in use. lets start with 400 MFD

Two #12 wires from L2 wild 5 hp motor contact to right side of top and bottom caps in column two. Jumper wires between. same 400 MFD.


Two #12 wires from L3  25hp motor contact to left side of top and bottom caps in column two. Jumper wires between each cap in use. lets start with 400 MFD

Two #12 wires from L2 wild 25 hp motor contact to right side of top and bottom caps in column two. Jumper wires between. same 400 MFD.

Note: then we can just add or remove jumper wires to change amount of caps




E: LOGIC WIRING

Self latching Master  Control Relay   (MCR)

wire        connection 1         connection 2         purpose
1              common^                  pin 2                        common
2              110 breaker            green  PB NO          start switch
3              green PB NO           pin 7                         close relay
4              110 breaker *           red PB NC               stop switch
5              red PB NC                pin 6                         relay latch
6             pin 8                          pin 7                         relay latch


motor 1      contactor

11           common^                   contactor coil             common
12           110 breaker *            pin 1   MCR                 start power
13           pin 3 MCR                contactor coil             close contactor


motor 2      contactor

21           common^                  pin 2  timer relay           common
22           common^                  contactor 2 coil              common
23          pin 3  MCR               pin 7 timer relay            start timer
24          pin 7 timer relay    pin 8 timer relay            contactor 2
25          pin 6 timer relay    contactor 2 coil              start motor 2


* can also put at green PB wire 2 node
^Use white wire for common


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## Karl_T (Oct 17, 2014)

OK, today he got the panels mounted

I had given him the 20 and 5 hp. motors (plus the contactors, 3phase load center, relays, caps wires  - that's what dad's are for) and he went and bought another 20 hp at an auction. Turns out it was a smart move, even though my motor was labeled for 220 it was a 440 only motor.

He'll be wiring in the motors tomorrow.

I told him I got free time now or wait till March. So, he's dropping the diesel rebuild for a bit to do this.

Karl


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## Karl_T (Oct 17, 2014)

removed a double post


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## Karl_T (Oct 17, 2014)

Worked on the kid's phase converter a bunch today...

Logic wiring went quickly and had one contactor closing then the second closing five seconds later without any trouble.

Closed circuit breaker to motor one (5hp) and nothing happened. tore contactor apart and found a lose connection - problem solved.

Started motor one and it shook so bad an old 20 hp motor fell off the table. Too much capacitance.

Pulled 100 MFD cap off and accidently touched the case - POP!!!  <brown and yellow spots in my shorts>  I really need to add a bleed resistor to drain voltage off the caps. I know a EE type to ask for what would be the correct size.

Figured out 300 MFD was a nice amount of caps to start the 5 hp motor

Next we tried the 20hp motor 2 - it blew the circuit breaker. Started playing with the amount of caps (went inside to shop weapons between each try - ended up ordering two CZ-58s on sale for $400 each) No joy after several trials.

Decided to give up here, and loaded the 20 hp. into my  truck to bring home and make sure the motor is not defective.

We played a bit more balancing voltages and have a 5hp phase converter system running so the kid can hook up his manual mill, lathe, surface grinder, pedestal grinder.

In discussions after we quit, we think a 5hp just isn't going to start a 20hp without a TON of capacitance.  "The kid" mentioned, "I bet it'd work if we had a pull rope to have it spinning". BINGO, the light came on - both motors are the same 1200 RPM. Put a loose belt and pulleys between the two. That way motor one would not just provide a low power three phase circuit but also get the large motor turning. This will be the next trail after confirming the motor is good.


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## Karl_T (Oct 17, 2014)

Breakthrough day!!!!

I had went to help the kid with his phase converter project last Sunday. He had purchased the wrong time delay relay, so I was not able to test my additional wiring work. I had to add a second time delay relay to bring in 900MFD start caps for 0.5 seconds to start the 20 hp motor.

The time delay relay came today. The system started right up. With minor tuning voltages are within a few percent on all legs. he now has a large saw, a bridgeport mill, a drill press, and a southbend lathe running.  The large CNC Matsuura mill is next.

I attached a pic of the phase converter box. The second file is actually a .MOV file or movie of it running. To see it run, download the .pdf file and RENAME it to .MOV

'EDIT' this forum won't allow this big an upload,sorry


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## Karl_T (Oct 17, 2014)

*Re: 25hp 3phase converter with load center*

didn't come out real well, but here it is on youtube:


http://youtu.be/3dwbWrbDetc


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## xalky (Oct 17, 2014)

*Re: 25hp 3phase converter with load center*

This is great info. I have a 15 hp home built rpc that uses start caps and run caps. I didn't build it myself, I bought with a machine. It works great. What's the advantage of powering the 20hp 3ph with a single phase motor? Trying to wrap my head around that.


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## Karl_T (Oct 18, 2014)

There is no single phase motor here. The 5 hp. is also three phase.

The advantage to using this is is startup load. I start a 20 directly in my large shop. It dims the lights on the whole place for a second. "The Kid" didn't want that. Getting a 5 hp 3 phase going establishes a 3 phase circuit to make bringing the 20 in FAR smoother. 

My original design was to not need to use start caps but that didn't work out. It would have worked if  pulleys and a loose belt were installed to couple the two motors. "The Kid" didn't want to do that cause it wouldn't lay along the wall nicely.  I would still suggest this concept to anyone willing to couple the motors.

Karl

PS If you follow my posts, you'll the the term, "The Kid" often. This is my only son, Jake. He's now 31, one hell of a machinist and CNC programmer, an FFL, and all around great guy. He's my best friend.


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## John Hasler (Oct 18, 2014)

*Re: 25hp 3phase converter with load center*

One of the ways to start an RPC is to spin it up with a single-phase motor.


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## xalky (Oct 18, 2014)

*Re: 25hp 3phase converter with load center*

Thanks for the clarification Karl. I watched the video and it definitely is a smooth startup. My 15hp dims the lights and grunts and groans for a second or two before it gets up to full speed.


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## Karl_T (Oct 18, 2014)

*Re: 25hp 3phase converter with load center*



John Hasler said:


> One of the ways to start an RPC is to spin it up with a single-phase motor.



Yep, several ways to skin this cat.


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## Salsa (Oct 26, 2014)

*Re: 25hp 3phase converter with load center*

My friend copied my 3 phase starter but modified the design so that it does not use a relay. He holds his finger on the button until it comes up to speed. 

Problem solved.

Don


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## spaceman_spiff (Oct 26, 2014)

*Re: 25hp 3phase converter with load center*

this is awesome

can you put a price tag on this project? If I ever get a full size VMC I may need to budget this in, and it sounds like it might be much less expensive than a retail 20hp converter.

how does the cost breakdown for the components?


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## Karl_T (Oct 27, 2014)

Well, I STOLE the load center, twice. Bought a second one just to get more 3 phase circuit breakers. They are valuable, but also not many looking for one. That means you can find one cheap if you scrounge. I won't guess where you'd end up.

"The Kid" got a 20 hp 3 phase motor for $100. That's a pretty good deal. I gave him the 5hp. Cheapest way to get a 5 is to buy it on a piece of equipment. 

With any luck you'll get the motor contactor for the 5 with the above deal. Other wise maybe  $20 on eBay. A 20hp might cost ya, I'll guess $75 on eBay.

You'll need  a box to put it in, stop and start push buttons, start caps, run caps, relays, time delay relays, wire, terminals etc. This stuff can hit a couple hundred unless you scrounge well.

This unit was designed to be deluxe and last the kid a lifetime. Its possible to go real cheap with a single motor, no balancing caps, just a push button to hold in the start cap, skip the load center, yada yada

Karl


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## spaceman_spiff (Oct 27, 2014)

Karl_T said:


> Well, I STOLE the load center, twice. Bought a second one just to get more 3 phase circuit breakers. They are valuable, but also not many looking for one. That means you can find one cheap if you scrounge. I won't guess where you'd end up.
> 
> "The Kid" got a 20 hp 3 phase motor for $100. That's a pretty good deal. I gave him the 5hp. Cheapest way to get a 5 is to buy it on a piece of equipment.
> 
> ...



Even a couple hundred would be a HUGE savings..A new 20hp phase converter is $1500 from american rotary...we are comparing apples to apples here right? Because if this is the same thing then I'm probably going to be referring to this thread when I get a big VMC...this would be awesome..

Is the load center required only if I plan on distributing the power to multiple machines? Most likely I'd just connect it to the VMC and nothing else. 

Where did you come up with the design? Any schematics? This would help so many people to be able to buy bigger and cheaper equipment!!


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## Karl_T (Oct 27, 2014)

This is the fifth RPC  I've built. each one nicer than the one before. I have three of them in use on my farm.

I'm not an EE,  don't read or write schematics. The first post has how to wire this one. When you get your stuff together, I (or someone else) can walk you through the wiring.  If you're after a schematic, they are out there on the web.

if you don't use a load center, put in a fuse block. Works fine for one or two machines.

From there, start scrounging. For me that's most of the fun.

Karl


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## spaceman_spiff (Oct 27, 2014)

Karl_T said:


> From there, start scrounging. For me that's most of the fun.
> 
> Karl



I couldnt agree more! I'm already amped up for getting my hands on a giant 3 phase motor!!!


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