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RPC starting to have trouble?

lavrgs

Aluminum
Joined
Sep 21, 2008
Location
Tualatin, Oregon
I have an Anderson Converters rotary phase converter - I can no longer find them-not sure if they are out of business or bought out; they used to be in AZ. It has been running for ten years and today I was not able to start the spindle on my mill. Eventually I spun the mill spindle by hand and it ran, but it is time to find the cause. I ran my lathe this morning without issue - it has 1 1hp motor vs 5hp for the mill. I have also been having trouble with another lathe and am starting to wonder if the RPC is causing those problems.
I know very little about how these converters work and I suspect some maintenance is in order. Any suggestions for what to check it would be appreciated
Voltages with no load EDIT REORDERED 247-256-256. with a load the voltages were 246-250-256
 
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I will take more some pictures - I see the black caps you refer to. see link below
This one isn't very clear
I will take some detailed picture to capture the wiring - would there be a standard (?) schematic or are they all different. This is a 7 1/2 hp unit. Maybe just a place to browse schematics to identify what I have
 
I have an Anderson Converters rotary phase converter -............................ It has been running for ten years and today I was not able to start the spindle on my mill. Eventually I spun it by hand and it ran, but it is time to find the cause. I ran my lathe this morning without issue - it has 1 1hp motor vs 5hp for the mill. I have also been having trouble with another lathe and am starting to wonder if the RPC is causing those problems.
I know very little about how these converters work and I suspect some maintenance is in order. Any suggestions for what to check it would be appreciated
Voltages with no load 256-256-247. with a load the voltages were 246-250-256
So what was it that did not start? Seems like it was the mill, not the RPC.

If so, then start capacitors are not in the picture, they have no effect once the RPC has started.

The voltages don't look too bad. But, which is which?

For the no-load readings, I suspect the first two are from the incoming legs to the generated leg, and the third is across the incoming leg, just because it is the one that is different. Is that correct?

For the voltages under load, are they in the same order? I suspect not, in that case, the first looks like the incoming leg, as it is slightly lower than the lowest of the unloaded legs, also suspected to be the incoming leg. Is that correct?

Finally, what load did you apply? Presumably the 1 HP lathe?

If the above educated guesses are correct, I would be looking at the connections in the wiring going to the mill and the other lathe, the machines that have problems.
 
The black caps are 270-324 uF 250vac made by BMI. Are there any capacitors that are better than others or does it not matter? Forgive my ignorance but do these caps affect the voltage? - mine seems a bit higher than I think is ideal
 
So what was it that did not start? Seems like it was the mill, not the RPC.

If so, then start capacitors are not in the picture, they have no effect once the RPC has started.

The voltages don't look too bad. But, which is which?

For the no-load readings, I suspect the first two are from the incoming legs to the generated leg, and the third is across the incoming leg, just because it is the one that is different. Is that correct?

For the voltages under load, are they in the same order? I suspect not, in that case, the first looks like the incoming leg, as it is slightly lower than the lowest of the unloaded legs, also suspected to be the incoming leg. Is that correct?

Finally, what load did you apply? Presumably the 1 HP lathe?

If the above educated guesses are correct, I would be looking at the connections in the wiring going to the mill and the other lathe, the machines that have problems.
Generally your assumptions are correct - I used the mill for the load, in spite of it having to be bumped . I should have taken all readings at the input to the mill but my no load readings were taken at the plug and resulted in different order.
The next question, if it's not the RPC the next area to look would be the VFD - I have a Unidrive on the mill so perhaps I need to call their support.
 
The black caps are 270-324 uF 250vac made by BMI. Are there any capacitors that are better than others or does it not matter? Forgive my ignorance but do these caps affect the voltage? - mine seems a bit higher than I think is ideal
Replace with oil filled types like on the right side of picture. They will last.
You would need 8-9 of them at 100 uF each. Yes, the drawback is the low capacitance per can.
 
Replace with oil filled types like on the right side of picture. They will last.
You would need 8-9 of them at 100 uF each. Yes, the drawback is the low capacitance per can.
At this point it does not seem that the start caps are a problem - the rotary converter is running fine, it's the mill having problems. I may have to look downstream from the converter
 
I removed the post about the start caps. You had the RPC running and then "spun it by hand" you mean the mill and not the idler motor.
Spinning the idler motor is a old technique. Anyway, your problem is not enough boost to start a 5 Hp motor but ok with a 1 Hp with RPC running.
I assume that when the mill motor is switched on it will spin slowly or make noise.

You could try turning on the RPC and running the lathe at say a medium RPM. Then switch on the mill 5 Hp motor. That should improve things.
But not a final solution. It will indicate that it take more juice to start your mill. If that is due to age of internal windings then there are two choices.
 
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You could try turning on the RPC and running the lathe at say a medium RPM. Then switch on the mill 5 Hp motor. That should improve things.
But not a final solution. It will indicate that it take more juice to start your mill. If that is due to age of internal windings then there are two choices.
I don't currently have the ability to run both machines. although I like the idea. I don't understand how adding more load will help diagnose the problem.
I am starting to think that the mill problem may be coming from the Variable Frequency Drive but you are implying it may be a motor winding problem...which would not be my first guess, since I have another machine giving me trouble and the RPC would be the common factor. With that said I ran my lathe 1hp without any indication of trouble. The mill and bigger lathe both have 5hp motors although the lathe is going through a retrofit and the issue seem to be out of the 3 phase area. I don't recall having spindle issues on the big lathe but I could check.
I am convincing my self that the RPC is ok and the mill has an unrelated problem. This exercise has put a higher priority on getting rid of that noisy thing 9-)
 
Oh, so now there is a VFD between the mill and the RPC.
Reminds of Paul Newman in Cool Hand Luke... "What we have here is a failure to communicate".

By running multiple target motors on a RPC system the T3 line becomes stiffer.
 
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The next question, if it's not the RPC the next area to look would be the VFD - I have a Unidrive on the mill so perhaps I need to call their support.
I had a VFD that was not starting a compressor. Changed the DC bus capacitors and got it working.
New VFD's track the running hours and tell you when to change them.
Something you can do with a soldering iron and a order from digikey.com.
 
As of yesterday afternoon I would call whatever problem I have "intermittent". My RPC is starting two other machines without issues. Yesterday I was able to start and stop the mill spindle so that is the focus.
Is there a way to mark a thread resolved?
 
I didn't follow up right away but the problem was a loose screw on the U leg ON THE VFD. All is good
That happened to me a few weeks ago on a VFD terminal to the motor.
My Allen Bradley VFD has Phillips screws for the terminals but the depth of the socket is too shallow. Makes tightening a problem.
A new Hitachi I have has screws that only my largest Phillips driver will fit. They got that right. What I do now is wick the motor leads
and VFD power leads with solder. Then there is a little more pressure I can put on the screw without totally mashing the copper strands.

Before the soldering days I would find connections that are loose but knew I had tightened hard enough. Perhaps the bundles of copper settled
differently under pressure? How else can the wire loosen like that. In total about 3 or 4 times.
Since the solder wicking I've had no problems.
 
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Good for you.

The solder does tend to have issues of loosening. If you have not, then maybe you are doing something specific that avoids that.

A better solution is a ferrule on the stranded wire.
 
I eat my spinach before a torquing on motor terminal screws.

There are junction characteristics that are introduced at large currents that are not great.
But the solder keeps the strands from spreading out. A ferrule is better.

Some power relays make quite a movement when switched. Long term vibration on the terminal screws.
 
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Solder has several issues.

1) it is very soft, and the screw has no definite" stopping point" when tightening.

2) Solder experiences "creep" during heating and cooling cycles, which leads to loosening.

3) Solder has considerably higher resistance than copper or aluminum.

4) solder has a low melting point.

5) In the case of severe heating during an overcurrent, solder may completely release the wire due to melting of the solder.

Those things make the use of solder as a binder for stranded wire a bit problematic. Even though many people "get away with it", I cannot in good conscience recommend it as good practice. Those who have no problems may simply not have had the conditions that cause the problems.
 








 
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