Troubleshooting 3 phase pump with VFD

stephendv
stephendv Solar Expert Posts: 1,571 ✭✭
in Solar Water Pumping #1
Hi all,

The 1.5kW deep well pump hasn't been running the last few days and when I went to inspect it today, the VFD was showing an error: "Over current on acceleration".
Pump is 230V phase to phase (which I believe is delta), same as the VFD. The VFD is programmed to slowly spin up to 50hz during about a 2 minute window. When I turn it on, it reaches about 10Hz and then shows the over current error.

I disconnected the pump and then restarted the VFD on it's own and it goes up to 50Hz fine without a problem, and there is voltage between the phases. It only shows the error when the pump is connected.
So I'd really like to determine if it's a fault in the VFD or in the pump.
I don't have any other source of 3 phase power so can't run the pump off another source. And I don't have any other 3 phase motor loads, so can't connect them to the VFD.
Have measured resistance of the windings and got back 4.8 ohms between phases and infinite resistance between each phase and earth.

Soooo, are there any other tests I could do on the pump or VFD, given my limited testing resources? I REALLY want to avoid pulling the pump out as it's 360ft down.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Troubleshooting 3 phase pump with VFD

    Do you have an AC Current Clamp meter?

    Measure each phase and see if you see any "differences" between the three wires. Also, clamp all three phases together and see if there is "significant" AC to ground current (short to ground).

    I was going to suggest that you put three light bulbs on the VFD--But it is probably using the feedback from back complex impedence of the motor and will not work correctly driving three lights.

    You might also try three 230 VAC filament lamps (one on each phase) to see if they light "evenly" as the VFD starts.

    Do you see any water flow? Could the pump motor be prevented from rotating (bearing failure, pump failure, derbies in pump, etc.)?

    My only guesses. Is there any debugging instructions from the VFD manual? Can you change programmed behaviour?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #3
    Re: Troubleshooting 3 phase pump with VFD
    BB. wrote: »
    Do you have an AC Current Clamp meter?
    Measure each phase and see if you see any "differences" between the three wires. Also, clamp all three phases together and see if there is "significant" AC to ground current (short to ground).

    Ok, have clamp meter, will measure differences. Regarding clamping the phases together, you mean connect all 3 output wires of the VFD together and then turn it on? Isn't that a dead short?
    BB. wrote: »
    Do you see any water flow? Could the pump motor be prevented from rotating (bearing failure, pump failure, derbies in pump, etc.)?

    Yep, might be, but would like to rule everything else out first before pulling that beast out :)
    BB. wrote: »
    My only guesses. Is there any debugging instructions from the VFD manual? Can you change programmed behaviour?

    Yep, can override everything, either by reprogramming or twiddling the knob on the front to set the frequency. The debugging instructions say that it could be a fault in the IGBT or in the current sensor... or a fault with the pump.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    Re: Troubleshooting 3 phase pump with VFD
    stephendv wrote: »
    Ok, have clamp meter, will measure differences. Regarding clamping the phases together, you mean connect all 3 output wires of the VFD together and then turn it on? Isn't that a dead short?

    Sorry, I was not clear... Put the meter current clamp around all three AC leads to the motor... Ideally, the total sum of the current to the motor should be zero amps. If there is significant current flow, then there may be a short circuit from the AC wires (or motor windings) to the well casing/ground.

    If you have a "stiff enough" AC inverter or generator 230 VAC single phase supply, you could get a motor start capacitor (or start capacitor plus one or two motor run capacitors) and a hefty push button switch and try to start the motor. See near the bottom of this page for some suggestions:

    http://www.allaboutcircuits.com/vol_2/chpt_13/7.html

    A couple of capacitors and a switch might be the cheapest way you can verify the pump operation.

    The motor will only get ~1/2 to 2/3rs (plus or minus) of its normal field energy on single phase, but it may be enough to prove if the motor is turning or not (push "start button", turn on AC power, count to 2 seconds, and release the start button... The motor will either be turning and pumping some water, or still stalled. You could monitor the current from one leg of the 230 VAC supply--You should get something like locked rotor current, then fall back to ~1/5th of locked rotor current if the motor is turning near full speed.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    #5
    Re: Troubleshooting 3 phase pump with VFD

    What is the make/model of your VFD and pump? Franklin is fairly common here in the states but I see that you're in spain.
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #6
    Re: Troubleshooting 3 phase pump with VFD

    Thanks Bill, will have a go with the current clamp. Can't easily get starting caps here- and having trouble hiring a 220V 3 phase generator too, might just have to pull the pump :(
    I phoned the VFD manufacturer this morning and they claim that if the VFD starts up fine without pump attached then the pump must be faulty. Which contradicts their manual, since the current sensor could still be faulty or the "IGBT" module.

    Wellman, the VFD is a 2.2kW IMO iDrive, the 220v version at the bottom of this page: http://www.imopc.com/pages/products
    Pump is a Calpeda 4SDF 22/28 EC

    Don't think any of those are sold much on your side of the pond :)
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #7
    Re: Troubleshooting 3 phase pump with VFD

    Maybe buy / borrow a new VFD controller, and try it out, maybe the old one is dead. Worst case is you have a spare now. I don't know if 10Hz will be fast enough to show any water flow.
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #8
    Re: Troubleshooting 3 phase pump with VFD

    Last night I reset the VFD back to it's factory default and then programmed the current rating for the motor to a value just lower than the VFD's limit. Pump is 1.5kW so told the VFD that the pump is 2kW. But it still exhibits the exact same behaviour, it seems to run at just under 10Hz for about 30 seconds then displays over current error.

    Using the AC clamp, measured all the output wires together (at 9Hz) and got 0.06A. Measured each phase individually, and the clamp meter couldn't settle on a value, I guess 8hz is way to slow. On 2 of the phases the AC meter was oscillating between 4.2A and 4.9A, but on the remaining one it was reading 3.9 to 4.4A. Don't know if this is enough of a difference to show a problem, given the low amps and slow speed?

    New VFD is about 300 euros, which I'd prefer not to spend if I don't have to :)
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #9
    Re: Troubleshooting 3 phase pump with VFD

    Nothing sounds "obviously bad" with the current clamp meter--I am out of ideas.

    Sorry,
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Ken Marsh
    Ken Marsh Solar Expert Posts: 114 ✭✭✭✭
    #10
    Re: Troubleshooting 3 phase pump with VFD

    Hi Steven,
    Just a couple thoughts,
    Two min is long time for spin up.
    I like to start pumps in more like 5 seconds.
    Some places in the RPM range there may be resonances where they hunt and can trip out the VFD on high current.
    It is more common to have trouble ramping down.
    Sometimes with difficult motors such as HVAC compressors you can not use ramp down.
    Current gets to bouncing and it trips out.
    Most VFDs give you the option of not using the deceleration ramp.

    It seems like most VFD troubles are bad connections or bad breakers.
    The supply current is drawn in high current pulses which seems to stress connections.

    VFDs are getting ridiculously low cost.
    They are less than a standard motor controller which they replace.
    I would have a spare around.
    But it seems like you are using a voltage changing VFD which may be more money.
    I have had no experience with them.
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  • Ken Marsh
    Ken Marsh Solar Expert Posts: 114 ✭✭✭✭
    #11
    Re: Troubleshooting 3 phase pump with VFD

    Hi Steve again,

    Am wondering how you came out with the well Pump.
    Read the thread a little more carefully.
    You say it ramps up to about 4.5 amp phase current where it kicks out.
    That is interesting since 4.5 amps would be full current for that VFD.
    The pump should not be drawing that much current until it gets up to speed.
    You have checked the obvious things and they sound good.

    So it doesn't sound good for the pump.
    Would suspect a stuck pump or perhaps insulation break down.

    As for current hunting, this is common for low inertia motors particularly when electronically driven.
    Things like air compressors and blowers are more steady.

    Let us know how it comes out.
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #12
    Re: Troubleshooting 3 phase pump with VFD

    Was away for the last 10 days, finally got a chance to pull the pump out yesterday. Took it to the pump guy and he stuck it on his workshops 230V 3 phase supply, which instantly tripped all the breakers. So it's looking like a short in the motor :cry:
    I mentioned the slow startup time to him, and like you Ken, he thinks that could be the cause of the problem. A 70m column of water sitting on top of the pump, and then the VFD trying to turn the pump too slowly which causes too much current draw, and may have burnt something out. The other potential cause could be the deceleration time, which I also recently (a few months ago) added to the VFD, so that instead of just cutting power to the pump it decelerates.
    Have ordered a new motor which should be here before the end of the week, and we have about 2000 litres of water left in the tank so we should be ok. Lessons learnt:

    1. Spin the pump up quickly with the VFD and
    2. Don't decelerate the pump, just turn it off

    Attachment not found.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #13
    Re: Troubleshooting 3 phase pump with VFD

    If the pump being driven by the motor is a regular centrifugal pump, (which the Calpeda 4SDF 22/28 EC is) then starting it at low speed or running it slow will not put any excess load on the motor, as at low speed, as in slow startup or slowdown, it won't be dealing with or fighting against the pressure of the big column of water above it. Instead, the built in check valve will be holding back that load, and all the slow turning pump will be doing is slowly spinning the water within it and gradually bringing it up to speed as the motor RPM increases, until it finally gets to the RPM where enough pressure is created to overcome the pressure against the check valve. With any centrifugal pump, it's greatest load is when it's actually MOVING water, air, or whatever. Think of your Mom's vacuum cleaner when as kids we'd put out hand over the input OR output, blocking airflow. The motor would not load down, rather it would speed up as the load was reduced. Same thing with centrifugal pumps. With it's outlet blocked, all a centrifugal pump has to do is spin the water within it, which is no big deal. Once the water starts flowing through the pump however, it has to work hard at constantly bringing new water up to speed, and the more water that flows through it, the harder it has to work.
    If the pump were however a positive displacement type, such as a piston pump, then that's a whole different kettle of fish, and would indeed act as your pump guy described.
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  • Ken Marsh
    Ken Marsh Solar Expert Posts: 114 ✭✭✭✭
    #14
    Re: Troubleshooting 3 phase pump with VFD

    Good job Steve,
    At least you have the equipment and know how to pull the pump.
    Wayne is correct, it is doubtful that the slow start up or the de-acelleration hurt your motor.
    The problem with long start up ramps is that the system can get to bouncing and trip out the VFD.
    But it should not hurt anything.
    It is just a nuisance.

    Was your motor decoupled from your pump when you tested it?
    I still suspect a stuck pump.
    Occasionally an impeller in the stack can come apart and lock the pump.
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #15
    Re: Troubleshooting 3 phase pump with VFD

    Thanks for the insights guys. My pump guy has already fitted the new motor and I'll be collecting it this morning. I asked him to check the pump itself when he disconnected the motor and he said it was fine. I'll double check with him today and also do a very short dry run above ground to confirm it's working before lowering it.
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #16
    Re: Troubleshooting 3 phase pump with VFD

    He Of The Pump said that the non-return valve was full of sand and my wife just told me that when we pulled the pump out there was a bundle of sand on top of it as it came out.... sooooo it may be that the borehole is filling up with sand. I see that the company who drilled the hole also offer a borehole cleaning service, but He Of the Pump says that he's heard of one instance where a client of his cleaned a borehole which then lost 3/4 of it's pumping capacity. Have you chaps heard of any similar issues with cleaning out boreholes?
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #17
    Re: Troubleshooting 3 phase pump with VFD
    stephendv wrote: »
    he's heard of one instance where a client of his cleaned a borehole which then lost 3/4 of it's pumping capacity. Have you chaps heard of any similar issues with cleaning out boreholes?

    Certainly. Depends on how you clean it out. If you are pumping high pressure water down the hole to flush out the sand, you are also driving that sand into the seams where the water enters the well. Over time the seams will often open up again (and your well will fill with sand again).

    The best way to do it is with a cable rig driller. They lower a long narrow bail bucket (on a cable) down the well and scoop out the sand without pressurizing it. Depending on the geology, the well may fill up with sand again.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #18
    Re: Troubleshooting 3 phase pump with VFD

    OUCH! If sand was in the check valve and over the pump, that means sand was being drawn into the pump and very likely "sand locked" the pump, stalling it and very likely damaging it. This sand would have caused what Ken had suggested, a stuck pump.
    My Grandparents had a drilled well, originally 109 feet deep, but over 30 or 40 years, it filled in with sand to the 75 foot level. We had to keep raising the pump to keep it above the sand. Since it was an overflowing well with plenty of supply, they could keep using it.
    Since that time, they have passed on, new people bought the property and drilled a new well, abandoning the old one along with the pump that's still down there somewhere and bulldozed the whole thing over.
    I've always wondered at the geological actions and forces that resulted in a layer of sand that far below the ground, down below bedrock. What ancient sea created that sand, and what actions buried it.
    BTW, the pump impellers etc are very likely now badly warn due to sand abrasion. :cry:
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #19
    Re: Troubleshooting 3 phase pump with VFD

    Ditto to VT's comments. We too had our 305' deep well cleaned with an old fashioned 'pounder' . It started as a 'near' artesian , came up from 300+ feet t 50 feet below the surface in our hole... now dropped to ~ 100 below the surface , still ~ 20 GPM.

    When he originally drilled the well, it was slow going through some volcanic rock at ~ 300 feet, when he broke through the bit dropped 8 feet in 3 'pounds', so fast, as he had reached for the shutoff as soon as it broke into the sand,...

    We then lined the bore with 5" PVC pipe with slits near the bottom, not at so that the sand would not be at the pump level, ~ 5 feet above the bottom, ie at the bottom of the volcanic rock. The PVC is large enough for the bailing bit to fit through.

    Only on occasion have we seen any sand come from the house tap, so the static level must have dropped due to the extreme dry conditions.

    hth
     
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  • Ken Marsh
    Ken Marsh Solar Expert Posts: 114 ✭✭✭✭
    #20
    Re: Troubleshooting 3 phase pump with VFD

    Oh Boy...
    I think you said that the well is pumping into a tank.
    You might want to see how much sand there is in the tank.
    You are fortunate to have a drop out place for the sand.
    Running sand into a distribution system causes real problems.
    Pumps can tolerate quite a bit of sand.
    The plastic impellers and diffusers tolerate it best.
    But the problem is, sand usually comes in slugs which can bind the pump.

    You might want to get your old pump motor back from the pump builder.
    It may be ok.
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #21
    Re: Troubleshooting 3 phase pump with VFD

    Hi all, thanks for all the insights!

    So this morning I finally had a chance to lower the existing pump + new motor down into the borehole again. Have been chatting to various people to try and figure out the sand problem, but in the end thought I'd take a chance and lower it and see what the quality of the first bit of pumped water was. And it was crystal clear! So it could be that the sand on the pump was accumulating over time(?) Checked the water entry to the water tank and it's arriving with a good amount of pressure so at least the impellers are still doing their job.

    I have a filter fitted between pump and everything else which accumulates a bit of sand and I have to clean it about once a month or so. The amount of sand it's collected is usually minimal, I'd say less than 2 tablespoons over a month.

    Still don't have a conclusive cause for the motor failure, you chaps have ruled out the VFD's accel and decel functions. There's very little sand in the water right now, so I'm pretty sure it's not submerged in a mud bath. Angry gods perhaps?
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,894 ✭✭✭✭✭✭
    #22
    Re: Troubleshooting 3 phase pump with VFD

    I might say that collecting rain water also might help make the pump last longer, but I won't because of the drought we are having in California.
    Water is just so very important is it not?
    "we go where power lines don't" Sierra Nevada mountain area
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #23
    Re: Troubleshooting 3 phase pump with VFD
    Dave Angelini wrote: »
    Water is just so very important is it not?

    Amen to that. Rain water capture is in the works, already have a 1000 litre tank for fruit tree watering, but really need to dig a storage dam then funnel both roofs we have into it. Long term plan though. Incidentally, we've had the wettest winter in decades, if I had a dam I would've been able to fill it entirely from roof captured rainwater.
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  • dannys
    dannys Registered Users Posts: 3 ✭
    #24
    Re: Troubleshooting 3 phase pump with VFD

    Take a look at Hitachi VFDs. I have a friend who's using a WJ200 Series drive.
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #25
    Re: Troubleshooting 3 phase pump with VFD
    dannys wrote: »
    Take a look at Hitachi VFDs. I have a friend who's using a WJ200 Series drive.

    As it happens, I botched the plumbing job- didn't tighten one of the l-bends, so pump came on, pipe came loose and drenched the VFD :cry:
    So found a very cost effective replacement from Fuji, came in at just under $200 for a 2.2kW VFD. Seems like a nicely made unit, huge heat sink on the back and very programmable.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #26
    Re: Troubleshooting 3 phase pump with VFD

    Is the Fuji water/splash resistant? :p

    Stephen, I am very sorry to hear what happened.

    VFDs seem to be dropping in price/becoming more cost effective.

    Keep us up on how it is working for you. I have talked to one person and read a few others that VFDs (probably the MSW type VFD) seem to cause short life for their motors (or at least more failures on VFD vs AC mains than they would have expected).

    I think VFD's are going to become very popular for off grid power systems and the various electric motor tasks.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #27
    Re: Troubleshooting 3 phase pump with VFD
    BB. wrote: »
    Is the Fuji water/splash resistant? :p

    Not yet, but I'm gonna put a BIG plastic bucket around it (with enough ventilation) to prevent future tears ;)
    BB. wrote: »
    I have talked to one person and read a few others that VFDs (probably the MSW type VFD) seem to cause short life for their motors (or at least more failures on VFD vs AC mains than they would have expected).

    Well I still don't know why the motor failed after only a few years use. My well guy says it's not the VFD and some of the comments on this thread seem to support that... but if the pump fails again, then I'll switch to single phase motor and power it directly from the inverter.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #28
    Re: Troubleshooting 3 phase pump with VFD

    My guess is that the "inexpensive" VFDs are MSW type devices (modified square wave). When running a motor, upwards of 20% of the current is not 50/60 Hz but some harmonic of the fundimental (the square shoulders of the MSW). That can cause motors to run hot.

    Don't know if that is a real problem or not--Just my concern. Would be interesting to run a VFD vs Grid power on a constant load motor (such as a fan or pump). Measure the RMS current and motor temperature to see if heating is an issue or not (in well pump, not so easy to measure temperature).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • dannys
    dannys Registered Users Posts: 3 ✭
    #29
    Re: Troubleshooting 3 phase pump with VFD

    If you had a NEMA 4X drive it would have been ok. The best NEMA4X drive that I have used is from TB Wood's (E-trac Series). TB Woods was sold to Vacon out of Finland. Now they call it Vacon X-Series but it is a very expensive drive. Is your FUJI drive their new FRENIC Mega Series?
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #30
    Re: Troubleshooting 3 phase pump with VFD
    dannys wrote: »
    If you had a NEMA 4X drive it would have been ok. The best NEMA4X drive that I have used is from TB Wood's (E-trac Series). TB Woods was sold to Vacon out of Finland. Now they call it Vacon X-Series but it is a very expensive drive. Is your FUJI drive their new FRENIC Mega Series?

    My bucket is cheaper than NEMA version ;) The Fuji is the FRENIC MINI version: http://www.ctiautomation.net/FUJI-FRENIC-Mini-Inverters.htm
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  • dannys
    dannys Registered Users Posts: 3 ✭
    #31
    Re: Troubleshooting 3 phase pump with VFD

    LOL. Cannot beat the bucket.
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