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Hydraulic Press brake Dropping Volts HELP

flagvan2000

Plastic
Joined
Feb 26, 2020
I installed a Hydraulic Press Brake. It is running a 10HP 220 volt motor. I updated to a 40 HP Rotary Phase converter. Using a north american soft starter Rotary phase converter Panel with a used WEG 230 volt 40 HP idler Motor.

The problem i'm having is When the Press has a load the incoming Volt Drop from 245 to 195-200 volts when loaded. Which kills the hydraulic power and can't bend.

I have also attached Picture of the idler motor i'm using for the rotary converter and a link for the soft start Panel

Rotary Phase Converter Control Panel CP-40

Does anyone have a idea what could cause this or what i could do to fix?162183-weg-cc0294-040360t3e286ts-40hp-electric-motor-208-460v-3ph-286tc-frame-3535-rpm-3.jpg162183-weg-cc0294-040360t3e286ts-40hp-electric-motor-208-460v-3ph-286tc-frame-3535-rpm-2.jpg162183-weg-cc0294-040360t3e286ts-40hp-electric-motor-208-460v-3ph-286tc-frame-3535-rpm-3.jpg162183-weg-cc0294-040360t3e286ts-40hp-electric-motor-208-460v-3ph-286tc-frame-3535-rpm-2.jpg
 
They are sending me a voltage boost panel that detects voltage drop. I was just seeing what other people thought. Don't understand why i'd need that. Would think having a oversize rotary would not give this problem
 
They are sending me a voltage boost panel that detects voltage drop. I was just seeing what other people thought. Don't understand why i'd need that. Would think having a oversize rotary would not give this problem

The linked document shows it balances within 2-3% or so, and has undervoltage protection.

Might the panel not be working properly ?
 
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The problem i'm having is When the Press has a load the incoming Volt Drop from 245 to 195-200 volts when loaded. Which kills the hydraulic power and can't bend.

What do you mean "incoming volts"?

Is that incoming to the RPC or incoming to the press motor?

Is that ANY wire pair? OR is it just the generated leg?

The RPC cannot fix voltage drops coming to it. A larger RPC CAN fix voltage drops on the generated leg. But, a larger RPC also draws more current, so if the problem is a weak SOURCE, the bigger RPC can make that worse.
 
What do you mean "incoming volts"?

Is that incoming to the RPC or incoming to the press motor?

Is that ANY wire pair? OR is it just the generated leg?

The RPC cannot fix voltage drops coming to it. A larger RPC CAN fix voltage drops on the generated leg. But, a larger RPC also draws more current, so if the problem is a weak SOURCE, the bigger RPC can make that worse.

The voltage that drops from 245 to 190-200 is after the RPC and going into the press. I'm getting 7 volt drop going single phase into the RPC
 
The two legs going into the RPC are the same as what comes out. Still might be interesting to see what exists at the motor, on the two "pass-through" legs as well as the "generated leg". There os wire between the two, so more drop is possible.
 
T3 is the generated leg. (White) T1-T2 drops from 258 to 200 volts. T3-T2 drops from 246 to 232 volts and T3-T1 drops from 254 to 200 volts. These are measured before the press with load
 
T3 is the generated leg. (White) T1-T2 drops from 258 to 200 volts. T3-T2 drops from 246 to 232 volts and T3-T1 drops from 254 to 200 volts. These are measured before the press with load

Are you sure?

Seems like the T1-T2 would be the 246 to 232 drop.... The other two are consistent with a generated leg drop.

It would be interesting to see what sort of current is being drawn. The normal full load current for the 10 HP motor would be 28A. the 40 HP idler should handle that fine.

In a mechanical brake, there might be a serious short term overload, taken care of by a flywheel. With a hydraulic brake, that is not a solution.

But, is there maybe a shift to a different pump rate that is supposed to happen, but is not happening? Some I have seen have one pumping rate that is basically a "rapid", and another slower rate used for finishing the stroke.

If that is the case, and the shift is not happening, there could be a totally ridiculous load and stalled ram situation.
 
What you need is an axial piston variable delivery pump/either swash plate or bent axis......all the makers make these ,a bit costly new,but there are loads of used ones about from mobile equipment....You will need a specialized open loop type ,preferably with a simple pressure /volume controll.In other words ,as pressure increases,delivery volume decreases ,thereby ,limiting power needed.
 
Are you sure?

Seems like the T1-T2 would be the 246 to 232 drop.... The other two are consistent with a generated leg drop.

It would be interesting to see what sort of current is being drawn. The normal full load current for the 10 HP motor would be 28A. the 40 HP idler should handle that fine.

In a mechanical brake, there might be a serious short term overload, taken care of by a flywheel. With a hydraulic brake, that is not a solution.

But, is there maybe a shift to a different pump rate that is supposed to happen, but is not happening? Some I have seen have one pumping rate that is basically a "rapid", and another slower rate used for finishing the stroke.

If that is the case, and the shift is not happening, there could be a totally ridiculous load and stalled ram situation.



There is a change in speed on the down feed of the press where it starts bending. it hit a limit switch which then slows it down. i can double check the T1-T2 tonight. i thought the same thing. but didn't seen to get that reading. Also with the rotary phase converter off shouldn't i still get the single power running through the panel?
 
The wire run from main panel to rotary converter to my press is 10 feet. and i'm using 4 gauge which is rated 85 amps. press pull 30 amps and the rotary with the press pulls 50 amps
 
Also i had our power company out yesturday. The main transformer that powers my house and shop is only a 15kva which i think is rated 60 amps. The press with the rotary would add to about that plus whatever else is running. They didn't think that could be the issues i'm having but i kind of think it could be some of it. Does someone have a opinion on that? With my cnc Plasma table, air compressor and the press brake going it could reach to 120 amp draw. rotary and press alone is around 50-60
 
I would put a meter on the incoming legs to the rotary and run the brake. See if the incoming voltage is dropping. If it is go back to the mains comming into the main panel and check that. Make sure the contactor in the brake press is still good. Best way to check this stuff quick is run it for a bit. Then check everything in all the electrical boxes with a flir.
 
I did the voltage test on the single phase side to the RPC the other day. I was getting a 7 volt drop. I just bought a Flir meter and will check. Do i just see if the contactor and breakers are getting hot? Is that what i'm checking?
 
Also i had our power company out yesturday. The main transformer that powers my house and shop is only a 15kva which i think is rated 60 amps. The press with the rotary would add to about that plus whatever else is running. They didn't think that could be the issues i'm having but i kind of think it could be some of it. Does someone have a opinion on that? With my cnc Plasma table, air compressor and the press brake going it could reach to 120 amp draw. rotary and press alone is around 50-60

The small transformer goes with a "several percent" drop on incoming voltage, which I suspect is your 7 volt drop. That drop is not quite enough to explain a 20% drop on the generated leg, but it would explain some of it.

You get drops on the generated leg from several effects:

1) You get a drop from the idler slowing down with load on the generated leg, which lowers the generated voltage (but it increases idler input current)

2) You get a drop because input voltage dropping induces less current in the idler rotor, so the "generator field" is less. (interacts with #1)

3) You get a drop because of impedance in the idler motor which drops voltage with increasing load current. (balance capacitors are intended to offset part of that)

Whether those effects add up to be the whole 20% drop, I am not sure. It could be quite a bit of it.

QUESTIONS:

A) Have you checked the current to the motor on generated leg and the "pass-through" legs during the press stroke?

B) Have you looked at the total single phase input current during the press stroke?

You have a big voltage drop, so your first response should be to see if you have a big current to go with it.
 
The small transformer goes with a "several percent" drop on incoming voltage, which I suspect is your 7 volt drop. That drop is not quite enough to explain a 20% drop on the generated leg, but it would explain some of it.

You get drops on the generated leg from several effects:

1) You get a drop from the idler slowing down with load on the generated leg, which lowers the generated voltage (but it increases idler input current)

2) You get a drop because input voltage dropping induces less current in the idler rotor, so the "generator field" is less. (interacts with #1)

3) You get a drop because of impedance in the idler motor which drops voltage with increasing load current. (balance capacitors are intended to offset part of that)

Whether those effects add up to be the whole 20% drop, I am not sure. It could be quite a bit of it.

QUESTIONS:

A) Have you checked the current to the motor on generated leg and the "pass-through" legs during the press stroke?

B) Have you looked at the total single phase input current during the press stroke?

You have a big voltage drop, so your first response should be to see if you have a big current to go with it.

Thank you for all you said.

When you mean current. You mean amps? i know on the single phase side of the RPC i have a large spike of amps when i am using the press.

I know i was getting 100+ amp spikes when using press last night.

If you could explain how i might go about testing these i would do it.
 








 
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