Power pack problems

[bottles]

Hi all,

Thanks to help before I have got my hydraulic power pack working. But as I have no info on this I am at a loss regarding the power pack drawing so many amps its tripping the fuse box? I was told the power pack came with a press that was used to push bearings and other garage type jobs. They never had the pack running so were getting rid.  

When I started to see how the pack worked I had the remains of a pressure needle (now missing). There appears to be two controls. one is a simple screw which increases or decreases the pressure. there is a second screw cap on the hose side of the solenoid that regulates the amount of oil going through to the ram.

 It runs well up to 1000psi drawing about 8 amps. When I increase the pressure to about 2500 the fuse trips in the fuse box.

I am running the 3 phase motor through a phase converter from a 20amp 240v  socket. What is slightly confusing me is the motor plate rates the motor as 4.7 amp at 415v or 8.1 at 240v.  

Do you think I have an issue with the motor (2.2kw/3hp) that is causing the overload? Or is it just a matter of setting the flow to a minimum for max pressure? Any other suggestions on getting this back working.

As an aside is there an easy  way to use a single acting ram with this power pack.?

Andrew

 

 

this is why we ask people to load the photos to the IFI site rather than off site places. we can do nothing to recover this

[knots]

Is there a manufacturer name and model number.  Can't tell much from looking at a picture.  

 

Can you tell if the hydraulic pump is a gear pump or a piston pump.   Pump type makes a big difference.  If not a gear pump it may not be intended to run above a 1000 PSI.  Also if  the phase converter is a static type converter you may not be getting full power.   Read the phase converter literature.

[Frosty]

How is the oil flow? Not the settings but the flow itself.

 

If the flow setting is too restricted then turning up the pressure could be putting too much resistance on the pump driving up the elec draw.

 

While I've never messed with an electrically driven porta power pump I used to have three gas powered ones to keep running for the casing jacks. the main problem I used to run into when they suddenly or gradually started putting needing much power to work is the check valve in the pump's internal valve block, not the control valve block the pump block. all ours were gear pumps, even the 10,000lb pump. Gear pumps are NOT transparent pumps/motors stop the output and one of two things WILL happen, it'll blow something somewhere OR stall the motor/engine driving it.

 

when you're testing any hydraulic system be sure to either stay away from any possible leak OR shield yourself from it. A high psi system and 1,000psi is close enough to open you like a knife, is a dangerous thing. A leak can fire an invisible jet of hydraulic fluid that will open you up before you know you've been hurt. It's also not very good to have much hydraulic fluid in your bloodstream.

 

Rule #1 trouble shooting is do ONE thing at a time and observe the reaction, changes, what breaks, explodes, etc. and WRITE IT DOWN. Develop a test sequence and follow it every change, this really makes this easier.

 

Number one before you even start it again, Check the hydraulic fluid, is it clear? Clean? Foamy? Go ahead and fish the bottom of the reserve tank with a CLEAN pickup magnet and look for shavings, chips, etc. If the tank doesn't have a magnetic drain plug.

 

Number two, make sure all the connections are clean and un-fouled, the hoses are in good condition and the control valves move freely. Pulling the hoses from the valve body and receiving tools is a good thing to be thorough.

 

The first thing on my trouble shooting list for symptoms as you describe is to gradually open the flow valve. Just a little bit at a time and pay CLOSE attention to the reaction of the electric motor. If no change occurs by the time you've opened the flow valve all the way it's time for #2

 

Now it's time to start closing the pressure bypass valve a little bit at a time. Observe and note reaction.

 

While you're test running the pump after each adjustment observe and note the valve reaction, you should be able to feel live hydraulics in the valves as a little resistance to movement that falls right off as the valve opens. this is normal and should be happening. It is subtle in small hydraulic systems though but it's there. If it doesn't go away or doesn't exist then you have THAT problem.

 

If the resistance doesn't go away as the valve opens then the valve either isn't opening OR the output side is blocked or restricted somewhere between the valve block and the return hose.

 

If there is NO resistance then there is NO pressure on the input side of the valve block.

 

OR if the valve squeals, the handle vibrates or chatters the problem is PROBABLY in the valve itself.

 

Everything you do after you turn it on will give you clue, listen take notes and only change one thing at a time. sometimes I've had to go through the entire test sequence every single change. I've spent days trying to trouble shoot these things but that was before I started figuring them out.

 

Yeah soils test drills and the supporting equipment meant living with hydraulic systems. I learned to LOVE hydraulics.

 

Frosty The Lucky.

[Steve Sells]

How did you measure what the draw was, what method?  older units can draw more than a new one from various service issues.. like bearring resistance, that the name plate can not address, because that rating is from the testing on that model when new and fully tuned. 

 

Code states 200% for continouis duty motor operation, so the 8.1 amp rating you state, now needs 16.2 amps suppling it.  PLUS thats the 3 phase rating, you are not driving it that way, you are driving it with 240v single phase, through a converter. I have no idea what converter you have   so I can not even guess how efffecient it is to calculate that for you,  the best  ones are about 80% eff. ratings  most are less (meaning to get 80 amps out of one you need 100 amps @ 80% because the remainder is converted to heat) but if you have a 80% eff rating you are drawing 20.2 amps,  so if you do not have a top of the line converter you need more. Simply you need at least 30 or 40 amp lines (again guessing on the converter you have ) to operate the motor and drive the converter at capacity with out problems.

 

also FYI  a install should be set to not be using more than 80% on average of the rating of that circuit.

[bottles]

Well I have finally had time to look at the power pack again. I tried frosty's suggestion on sourcing the problem. Unfortunately without success. Could be the low pressure, flow or the electric solenoids.

The tank has crud galore in the bottom, the oil is like milky tea. So I'm going to drain the oil and clean everything.

I suspect there may be issues with the pump. How difficult are these to take apart AND put back together and get working?  

Andrew

[knots]

If the pump stalled I would look at the other components first.   Did the phase converter come as apart of the package.   Some static phase converters a little more than a starter circuit.  After starting, the motor runs on two legs of the circuit giving 2/3 of the rated motor power (maybe).  

[bottles]

I already had the 4kw static phase converter.  I don't know much about these. But assuming a 1/3rd loss in power it should be able drive a 2.2kw motor without issues. The phase converter has an amp  meter.

I need to find time to clean everything and try and flush the system. Then try again with new oil etc.

[knots]

OK,  Back when I was researching access to 3 Phase power I looked at rotaty , and static phase converters as well as VFD's .  I eleminated static phase converters because I understood from the literature and on line conversations that motors powered by static phase converters did not run at full power.  My understanding at that time was that they ran at 2/3 rds power.  If my understanding was correct then there is a good chance that your 3HP motor is providing only 2HP when you need 3 HP.  If that is true then your stalling problem could be the result.  

 

Based on that understanding I elected to build a rotary phase converter for my Vertical mill and use VFD's for four other  machines.  Since I am not an electrical genious, and only have a cook book understanding of the subject, you should confim the validity of this for you phase converter/motor combination.  

[knots]

This article seems to express the consensus of opinion of static phase converters.   

 

 

http://www.woodweb.com/knowledge_base/Static_Versus_Rotary_Phase_Convertors.html

[timgunn1962]

Bottles, where in the world are you?

 

From what I can make out, most US phase converters are 240V output, whereas most European ones have an autotransformer to give 415V output.  In both cases, the third phase is shifted using a capacitor (or several) and this doesn't usually give perfect 120 degree phase angles, causing an imbalance between the voltages on the motor phases. The voltage imbalance means the current is also imbalanced and when the hardest-working winding is at rated current, the other 2 will be doing a bit less, hence the derate. It's the motor that needs to be derated, not the converter, so your 3 HP motor might effectively become a 2-and-a-little-bit HP motor.

 

I've not played with hydraulics in decades, so I'm rusty, but I think I understand what you've got there.

 

Almost all hydraulic pumps are fixed-positive-displacement pumps, which means the flow through the pump is directly related to the pump speed. On a fixed-speed motor, it's effectively fixed.

 

The amount of work done per pump revolution depends on the pressure. More pressure, more work, more current drawn by the motor. The pressure is set using the relief valve. Once the pressure is high enough to crack the relief valve, the pressure will be maintained at the relief valve setting as the relief valve dumps the oil back to the tank.

 

Once there's clean oil in the system, I'd proceed as follows:

 

Back off the relief valve fully. Start the pump and measure the current in each of the 3 phases. Find the one with the highest current and leave the ammeter on it.

 

Wind in the relief valve and watch the current come up. When you are approaching the rated current for the motor, check all 3 phases again and pick the one with the highest reading. Adjust the relief valve until it is reading rated current and lock the relief valve. check all 3 phases again to make sure none is drawing higher than rated current.

 

At this point, take a look at your pressure gauge, if it's working. Whatever it reads is the maximum you can get without overloading the motor. It might not be what you want, but you are stuck with it. From your original post, it seems it might only be around 1000 PSI.

 

Next step is to sort out the valving, connect your cylinder and see if you can live with what it is giving you.

 

The flow control is best left wide open unless you find you need to reduce the ram speed. It's just a restrictor and basically causes the relief to open earlier than it would otherwise.

 

On a simple hydraulic setup like yours, you don't have the facility to adjust the relationship between flow and pressure.

[knots]

From yet another source

 

"Static conversion techniques in which the motor is run at less than full efficiency mainly on two of the legs of the three phase motor. Current is sometimes injected into the third leg with a capacitor or transformer arrangements that provide imperfect phase shift. In these systems the motor must be derated.  "

[bottles]

So if my static converter will actually under power the motor, would using a 240 VFD give full power? Having a busy time with work so haven't had time to look at the power pack.

Tim I live in York, you have seen my workshop when you helped with my siemans VFD.

Andrew

[timgunn1962]

Hi Andrew.

 

I think I can remember your setup: static phase converter into a 3-phase 415V Siemens minimaster 420  VFD. The VFD seemed pretty meaty so I assume it was at least 3 HP. The VFD was running a grinder when I was there.

 

It's a bit more faffing about, but I'd expect you could run the power pack from the Siemens VFD. I think (though I'm not 100% certain) that the VFD will deal OK with the phase imbalance, even at full load. The VFD should be able to display current, so setting the relief valve wouldn't need a separate ammeter.

 

I think you'd need a separate power feed to run the solenoid valves, but that shouldn't be too big an issue.

 

Regards

 

Tim