How to setup a 3-phase 240V to 480V transformer?

I just bought my first lathe, which is a Rivett 1020S, and I'm obviously excited and ready to get it running. The motor is a 3-phase

5HP 240/480V and it is currently wired for 480V.

I plan to setup a phase converter using at least a 3-phase 240V 10HP motor.

I've never setup a transformer to increase the voltage from my converted 3-phase 240V to 480V and so I'm seeking advice on this.

Instead of the 10HP 3-phase 240V motor for the phase converter, will I need to increase the HP any? Does this motor need to be a 240/480V?

Thanks in advance for any advice.

Reply to
Mark Main
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Mark, you made me confused, why don't you rewire the 240/480 lathe motor to run off 240V? That would be easiest and would not require buying a bulky, and costly transformer, as well as eliminate transformer losses.

Reply to

When I open the power panel on the end of the lathe I see the 3 wires for the service power... but those wires hook into what looks like a fairly complex power panel (I think it's the original Vari-Drive), and from that it leads to the motor. I've never rewired a motor from 480V to 240V.

I would prefer doing this the simplest way possible and so wiring 240V would be great if I knew how to do it. Thanks.

Reply to
Mark Main

Greetings Mark, We need the motor data to help you. Someone here should be able to tell you how to connect the motor for 240 volt operation. If the motor is dual voltage then it makes sense that the control electrics will also work with either 240 or 480 volts. Anyway, if you have 240 volt service, then it will be lots easier and cheaper to build a 240 volt rotary phase converter and change the internal motor connections. It's not like you need to remove the motor windings and have it re-wound. The motor will probably have 9 wires that can be connected two different ways for either 240 or 480 volt operation. A common wiring configuration is having the wires numbered 1 through 9. For 480 volt operation the wires would be connected thusly: 6+9, 5+8, 4+7, with wires 3, 2, and 1 connected to the power. For 240 volts the connections are: 6+5+4, 9+3, 8+2, 7+1, with the power again connected to wires 3, 2, and 1. Of course, since this is a three phase motor, swapping any two of the three power wires will reverse the motor. I bet someone here has the actual wiring specs for your lathe. ERS

Reply to
Eric R Snow

Reply to
Mike Berger

Mark, This is entirely doable. I have a RPC giving me my 240 3 ph. It is wired into a 240V distribution panel and a transformer. The transformer takes 240 3ph in and 480 3ph out. Then I go into a 480 distribution panel. The cost of the used transformer, panel and wiring was about $300.

I had one piece of equipment that was impracical to convert to 240 from

480. The coils for the starter would have had to be changed, everything else switched, so I wanted to run it on 480. 2 other lathes were 480 only. I can run smaller wire and the large motors start easier on high voltage.

This was especially proven to me on my air compressor. On 240 I could not start it when cold. On 480, the compressor starts much easier and faster.

Now I have the option to run most equipment and not have to worry about converting.


Reply to

Thanks to all for writing in and helping. I've been working tons of overtime hours and so I had to wait for the weekend to look at the motor.

I looked at the wire diagram on the motor and it's exactly as Eric stated. I only see lables for wires 1, 2 & 3 from my motor and so I'm going to try and figure out which wire number belong to the others.

The motor has the following listed on another plate:

Star Kimble

5 HP Constant Duty 60 Hz 13.4/6.7A 220/440V 1690 RPM 254 Type/Frame

Let me know if you need any other information. I've taken some pictures but I misplaced my cord to load them into my computer. I'll find it and load them for you to see close-ups of stuff.

Thanks again to all for your help.

Reply to
Mark Main

According to Mark Main :

[ ... ]

Hmm ... what media in the camera? CF, SD, one of the others? There are quite inexpensive USB devices in your local computer store (I've found mine in Micro Center, FWIW) which will allow you read the cards directly into the computer without the camera being involved. It is much faster than doing so from the camera, and it is less strain on the camera's battery as well.

You do know to post the images to the dropbox, not to the newsgroup, I hope? The instructions can be found on the dropbox.

Enjoy, DoN.

Reply to
DoN. Nichols

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