Phase converter question

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sw_ross

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I have a local restaurant that has a 3P dough mixer, the building is single phase, so they have a phase converter just for this machine.

I think it’s a rotary phase converter but I haven’t seen it yet, I’m going to look at it tomorrow.

Problem is that the kitchen staff turns on the converter to operate mixer but when they’re done they forget to turn off the converter so it continues to run, sometimes for days (apparently).
The maintenance guy thinks the converter is not operating like it normally should and Thinks that it’s because the thing is left on. He says the outer case gets hot enough to burn skin if touched.

I’m trying to think if there’s a way to have the converter automatically shut down when not being used. It obviously can’t shut down while being used or the dough will be ruined.

Can anyone offer any suggestions about doing this?
Thanks
 
Continuous operation is not the problem.
What's the actual temperature? Electrical apparatus running at letgo temperature (~70°C) isn't any cause for alarm.

Has anybody done routine maintenance on it recently? Its cooling-air passages might be clogged with crud or the bearings might be dry.

While there isn't necessarily anything wrong with the phase converter, there might be a problem with the workstation. The phase converter might need to be mounted out of reach, or caged, to protect employees from burns.

The obvious answer is to reconfigure it and wire the on-off switch ahead of the phase converter.
A time-delay relay might be needed to avoid starting under load.
 
Thanks for the advice. I’m going to look at it tomorrow. I’m not even sure where it’s located in relation to the piece of equipment.
They said it’s at least 12 years old at this time.
I’ll look at cleaning it, etc
 
The maintenance guy sent me the nameplate for the motor (dough maker);
6FF79F63-CFA6-4FB9-A6B9-222657CEC689.jpeg
It’s kind of hard to read, but my question is related to the “Motor Type: 2P/4P”?
What is that?
Also, the top line that says “xxx Max”- what would that be?
Thanks
 
A little confused here…
The enclosure for the capacitors has a transformer attached to the side of it-
I assumed it was to adjust voltage since the motor nameplate for the mixer is 208.
But when I fire it up the load side of the disconnect (feeding the mixer motor and the phase converter motor) is 240, L1-L2-L3….
FD3ED9AA-80C3-4CC0-8621-6FCD34922B6D.jpeg
 
sw_ross said:
A little confused here…
The enclosure for the capacitors has a transformer attached to the side of it-
I assumed it was to adjust voltage since the motor nameplate for the mixer is 208.
But when I fire it up the load side of the disconnect (feeding the mixer motor and the phase converter motor) is 240, L1-L2-L3….
View attachment 2567034
Click to expand...
Would the auto-transformer be used to make voltage adjustments to the derived phase only?
 
sw_ross said:
Would the auto-transformer be used to make voltage adjustments to the derived phase only?
Click to expand...
They can be used that way, to boost the generated leg, with a small capacitor for fine tuning of the voltage balance. But with the photos provided we can’t tell much from here.

The converter is small enough that it may be adjusting the input to the converter. And the caps may be just for starting duty.

What is the voltage input reading to the converter? From the building circuit Is it 208 and the transformer bringing it up to 240, or is the transformer just wired just to the generated leg from the RPC idler motor. Better pictures could help.
 
I am not sure where my first answer went regarding the use of a variable frequency drive to generate the 3-pahse power from single phase (there are some that will, see, for example, https://vfds.com/blog/can-a-vfd-convert-single-phase-power-to-three-phase/). That would allow you to operate the mixer directly at the VFD leaving the mixer switch on and having only a single place to turn the mixer on or off, making shutoff of the entire system foolproof. However, after sleeping on it, I recalled an easy solution that is also less expensive. Instead of using a switch to power the phase converter, connect its input to a mechanical timer like the one at https://www.amazon.com/Intermatic-FF6H-6-Hour-Plastic-Brushed/dp/B000B8WJZU/, Then if someone forgets to turn it off, it will turn off on its own only a little while later. Depending on current ratings, instead of using it directly, you may need to have it energize a contactor to turn on the phase converter. I used this approach with an air compressor putting the timer in series with the pressure switch after forgetting to turn it off a few times, and it has worked out well. Usually you have a pretty good idea of how long you are going to use a piece of equipment, so you can just set the timer for a little longer.
 
sw_ross said:
The maintenance guy sent me the nameplate for the motor (dough maker);
View attachment 2567016
It’s kind of hard to read, but my question is related to the “Motor Type: 2P/4P”?
What is that?
Also, the top line that says “xxx Max”- what would that be?
Thanks
Click to expand...
That is NOT a motor nameplate! Whoever saw a motor nameplate with a "LARGEST MOTOR" rating?? Also a MODEL 92 motor would be a bit unlikely. What you got appears to be from the mixer itself so the installed motor is compatible with the rest of the electrical and mechanical parts of the mixer. TYPE 2P/4P almost certainly is 2 or 4 poles so the motor will have a synchronous speed of either 1800 RPM or 3600 RPM at 60 Hz.
sw_ross said:
The maintenance guy sent me the nameplate for the motor (dough maker);
View attachment 2567016
It’s kind of hard to read, but my question is related to the “Motor Type: 2P/4P”?
What is that?
Also, the top line that says “xxx Max”- what would that be?
Thanks
Click to expand...
 
jdtm said:
Then if someone forgets to turn it off, it will turn off on its own only a little while later.
Click to expand...
Couple of things here-
First, if you're going to use a VFD, put the timer in a control lead to the VFD, not in the power supply; much easier.

Second, it's generally a bad idea to place anything other than a safety disconnect (or load reactor) between the VFD and the motor. Do not use the VFD as a phase converter and the control the mixer with it's integral switch.
 
ActionDave said:
Can't read the nameplate on the transformer and can't tell from the picture what it is hooked up to.
Click to expand...
It is hard to tell for sure from the picture, but it looks like the only wires entering the transformer are the black and red ones from the box with the capacitors. Again it is difficult to be sure, but it looks like these two are connected to the transformer via the two vertically-oriented wire nuts, while the ones that are roughly horizontal are for internal transformer connections. That would suggest that the transformer is being used as a reactor.
 
jdtm said:
transformer is being used as a reactor.
Click to expand...
I'm not seeing a restaurant with small single phase service and equipment most likely controlled by magnetic contactors as being concerned with harmonics

Maybe I'm wrong, but I doubt anyone involved in the installation even knows what IEEE 519 is.

Here is ronk's website

ronkelectrical.com

Phase Converters

Ronk powers industrial, utility and transportation sectors with American made electrical solutions, including transfer switches and phase converters.
ronkelectrical.com ronkelectrical.com
 
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