HF spindle problem with danfoss inverter

[daedalus]

Hi,

I have a danfoss vlt 2807 inverter that im trying to use to drive a excellon 820 spindle. The problem is whenever i start the drive with the spindle attatched i get an error 16: short circuit. Without the motor attached the drive starts ok.

This error should mean that one of the windings is shorted, but by measuring the winding resistance between each of the 3 terminals i get 10 ohms, so no short.

Anyone have any ideas whats wrong? surely if there was a short i would pick it up with my multimeter.

[fkaCarel]

I've checked a couple of things. Motor windings resistance checks up and about, my motor is 0.75kw, resistance ~7.5 Ohm, so maybe your motor is a little smaller. I tried blocking and after a couple of seconds i get "OL2", but then I don't have error16 in my book. It is possible that the motor just can't accelerate. Try adjusting the acceleration parameters to a very conservative value, or try the motor without it driving anything.

Carel

[daedalus]

the motor is integrated into the spinde, but it spins freely, so theres next to no load on it. The spindle is quite old, so i had some trouble getting the specs, but i think its 200v 1hp 1000hz rated, although im only going up to 450hz, as my drive cannot do 1hp at 1khz (drive derated by 60%).

i have had the ramp up time as high as 1500 sec, and still i get the error message pretty much instantly, although the spindle does move slightly before the error occurs. Also i have noticed that another code sometimes flashes up for an instant before error 16. i think its error 14: earth fault.

what i dont understand is if these faults exist why i cant pick them up with my multimeter.

[fkaCarel]

That leaves a couple of questions: is the spindle motor really 3-phase? The frequency is amazing. If it is, is there maybe a short from the windings to earth, causing error 14-->16? Does the inverter work with another motor?

Carel

[Al_The_Man]

Originally Posted by daedalus This error should mean that one of the windings is shorted, but by measuring the winding resistance between each of the 3 terminals i get 10 ohms, so no short. Anyone have any ideas whats wrong? surely if there was a short i would pick it up with my multimeter.

It is almost impossible to detect a short circuit with an ohm meter on a three phase motor, this is due to the inherent low DC resistance of the winding which if it is 10 ohms, a shorted turn is undetectable with this method.
You mention any of the three terminals, so I suspect you have a three phase motor fed from a single phase inverter?
If you could find a source of 200v~240v 3ph 50hz, you could run it direct and check the windings with a clamp-on ampmeter which is the best way to test for shorted winding.
Al.

[daedalus]

fkaCarel: im sure that the motor is 3 phase, as ive found other hobbyists using the same spindle. I cant detect an earth short with a multimeter.

Altheman: your right, the inverters single phase input. Unfortunately i dont have access to 3 phase power, or another 3 phase motor to test the drive with. That said i doubt its a drive fault, as with no motor connected it starts ok.

I may be able to get a new stator for this spindle, but i will have to totally disassemble the bearing assembly to replace it, which is a job i was hoping to avoid. I have another spindle i may try with this, which is the excellon 1010, but i need to find a connector for it. Is there any way to detect a winding short on a motor like this?

[daedalus]

ok, looks like a new stator will set me back $280, and ive just done another test which may shed some light on the problem. I have a second spindle, an excellon 1010 drill, and im getting exactly the same behaviour with that, spindle spins about 1/6 a turn then error 16.

Now both spindles are salvage, so may have faults, but were bought from different retailers on ebay. If i have to replace the stators i will do, but obviously for the price i just want to make sure it couldnt be anything else.

things i havent done:
set the correct reactance for the coils (using drive default)
set the correct U/f ratio (dont know it)

there is also some cryptic note in the vfd manual about motors without phase insulation paper requiring an external LC circuit.

could any of these things cause the response im getting?

[daedalus]

Ok, almost burnt a tonne of cash on replacement stators, then i had a thought...

what if the stator voltage is too high, and my specs for the spindle are wrong...

well running at 0.55kw 100v the spindle works fine
at 0.75kw 200v it has an insulation error

does anyone here know what the actual voltage rating is for an excellon 820 or excellon 1010 spindle??

[Frizz]

Hi daedalus,
i´m late, but can you tell me the configuration of your danfoss. The spindel is still working?
I´ve got that spindle to.

regards Fritz

[daedalus]

hi, the spindle is boxed somewhere at home, will try and dig it out next week. If you haven't bought a danfoss yet may i suggest you download and read the manual, as at the frequency these spindles run at you have to heavily de-rate the drive, and as such need to buy quite a bigger drive then you might expect (the mistake i made).

[Frizz]

Hi, thanks for your reply,

you are not working with any excellon spindle any more? If you have any idea wich kind of frequency converter will fit to my excellon quiet drill 820, please lat me know this.
regards fritz

[Frizz]

Originally Posted by daedalus does anyone here know what the actual voltage rating is for an excellon 820 or excellon 1010 spindle??

If still necessary:
(i found in a Excellon handbook from 1976):
Excellon Quiet drill 820 (now Jevco QD820)
1000Hz 60.000 RPM 270VDC
500Hz 30.000 RPM 140VDC