Motor starting via inverter/phase converter?

I've just been playing with my latest toy, I need to make some decisions about the electrics before finally putting it in place where it will be less accessible. It has a 10hp motor, though it left the factory with one nearer 20hp with an electromechanical variator-type drive but that has all gone. 10hp will be more than enough for me! It has a continuously-running motor with clutches . I can start it OK with my 10hp-ish (Andrew, did you work out an 'official' rating for it?) phase converter (with 10hp idler motor). It struggles though when engaging the clutch for speeds around 1000 rpm and up, much above 1000 and it'll trip the supply breaker for the converter. What it would be helpful to know is, would running the motor via an inverter (fed from the Converter) ease the pain? I feel that it might, as the phases the motor 'sees' will then be properly balanced. I suppose another ploy might be, if high speeds are needed, to engage the clutch with the speed turned down on the inverter and then bring the speed up, that ought to help a bit. There's a wattmeter on the machine, which uses a current transformer in one phase and a 'mystery box' to make an artificial neutral. It's showing a peak of about 10kW when I engage the clutch at 1000 rpm with just the chuck, no work in the machine. Is that likely to be bothered by use in conjunction with an inverter? I envisage having the inverter 'last', ie connected direct to the motor and supplied via the original control gear and wattmeter.
Thanks Tim

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Tm
As you know I use the converter/inverter hybrid just to manage current draw on start up. It might be worth rigging it up, not using the clutch and letting a slow ramp up manage the current draw.
Charles

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Charles
I'm reluctant to do it that way, as the machine is designed around clutch operation with, for instance, an electric spindle brake which comes on when the clutch is disengaged. I'd really rather keep all that, so what I'm asking is will the inverter give a benefit in the continuously-running motor situation (because the phases to the motor will be better balanced than direct from the converter, or for any other reason)?
I don't expect to often need speeds over 1000 rpm, but if they're there (up to 2000) it would be a shame not to be able to use them.
Tim

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Certainly the brute that I've got creating 3ph-415V for the grinder will drop the frequency and voltage when I DOL start the grinder motor. I programmed it with a realistic number for maximum motor power to avoid taking out the fuses. If the one you use can behave in a similar way, then it'll protect the supply by limiting the load the motor can draw when you put the clutch in.
Might have to look at manuals or ask suppliers to make sure you get one that can do that rather than just dropping out on overload.
Mark Rand RTFM

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I'll need to do something, I think, it took several attempts to start the motor this morning from 'cold', it was fine to restart once it had been run for a few minutes. I think a cold winters morning might be a serious problem! My problem is that I need the workshop useable for Monday morning, got an engine job coming in that'll need some machining, and there's this bl**dy great lathe smack in the middle stopping me using anything so it has to be put in it's place over the w/e. Was thinking of simply interposing an inverter into the final wiring to the motor at some later stage, but have twigged that it has star-delta starting with the starter gear in a box at the tailstock end so not so simple to do, and the box containing the motor connections will be hard against the wall. It'll need a bit of head scratching before diving in. I've got an 11kW inverter here which might do the job (Parker/Eurotherm SSD605), I'll have to try a lashup over the weekend with that though I don't have a programming panel for it.
Thanks Tim

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You sure Railtrack hasn't got any *spare* 3 phase up the bank ?
John S.

On or around Fri, 19 Jun 2009 09:23:37 -0700 (PDT), Tim
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I have this with the (underpowered) student. on cold days, you have to start it running at a medium speed about 5 minutes before you want to run it at high speed, in order to let the oil warm up, otherwise the gearbox is too stiff for the motor output in high speed (1200)
That's a 2HP single phase on a machine that should be 3HP 3-phase.

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We've got 11kV 3-phase overhead in the garden, bit risky tapping in to that though......
Tim

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We've got 11kV 3-phase overhead in the garden, bit risky tapping in to that though......
Tim
Watched edf change a radio controlled isolator on the 11kv line through my place last week - an amazing process with lift cradles and long insulated poles. They hung a large notice on the pole instructing passers by not to distract the staff, but I don't think my geese can read <G>
AWEM

On 19 June, 22:55, "Andrew Mawson"
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Having seen a broken 11kV line lying on the undergrowth, still live, & seen the effects it's not something I would want to mess !!
More seriously, the 11kV ends at a transformer pole maybe 30 metres from my workshop, supplies us with single phase and the railway with 3- phase. If I was starting again I would certainly enquire about getting 3-phase installed.
I've now established that starting the lathe motor is easier if I make sure the 'overdrive' high speed range isn't engaged, releasing the spindle brake might help as well, I'll try it later.
Tim

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It
Blimey is that three phase converter STILL running - I made it YONKS ago <G> it was originally one of a pair that I made to drive the MOOG Hydropoint - one for the beast itself which was about 10kw - and one for the compressor - which was a Prescold cold room compressor of about 7.5 KW. Both had single phase starting currents of well over 100 amps. I'm not sure which one you had. If I remember correctly the capacitors came from Bob Minchin in Romsey. Not sure which one you had, but I did see the other one on ebay about a year ago. Incidentally my company fuse stood the torture for several years but when it finally failed I found it was only an 80 amp one !!!!
AWEM

On 18 June, 20:57, "Andrew Mawson"
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And why shouldn't it be? <g>
I'm relying on it seeing me out, I wouldn't fancy having to buy a new one....
Tim

Andrew Mawson wrote:
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I was just reading this thread and wondering if it was the converter Andrew made from the capacitors I had. Andrew, you may care to know that the motor you swapped them for is still doing sterling work on my compressor.
Going back to the Tim's problem, the controlled start up that inverters provide can get the most out of a given supply without popping the fuses I'm assuming that the heart on the converter is a step up transformer. This should power an inverter OK. All inverters I've played with will accept 415 volt single phase in. Not one has a test for all phases present.
Good Luck
Bob

Colin Gibson at the Inverter Drive Supermarket should be able to advise. He provided me with excellent advice converting my Chippie and I know he works with much bigger stuff as well. www.inverterdrive.com Only connection with the company is as a satisfied customer
Regards
Stuart
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