800w spindle - noise & controlling remotely

[EddyCurrent]

Looks like section 6.18.3 shows how to configure the display to show motor speed.

[HankMcSpank]

Great so is it running yet.? . . . . If not why not. . . . . .Think you'll like it.!!

Unfortunately I'm not going to get a chance to wire it up for a little while yet (probably some time over the weekend)....got to think this one through & decide just how 'integrated' (wiring wise, remote control, speed control etc) I want to make it for my present or predicted method of working.

I'm figuring most folks have their VFD actually mounted near the machine?

The non-working machine I bought had its VFD tucked away in the 'enclosed' control box (well that is, before the VFD stopped working & they removed it!)

[JAZZCNC]

I'm figuring most folks have their VFD actually mounted near the machine?

The non-working machine I bought had its VFD tucked away in the 'enclosed' control box (well that is, before the VFD stopped working & they removed it!)

I prefer to have it near machine so can see the Amp's it's pulling while cutting. I set the RPM then display Amps and just have Start/Stop under machine control.

[HankMcSpank]

Oh dear....what is it about the CNC genre?!!!

So I've just hooked up my new VFD to my 800W spindle - the VFD is tripping outwith an overload condition.

I'm figuring it's likely to be the spindle becuase it's of unknown status. I bought the CNC machine in a "needs putting back together" condition ...with a VFD missing. I'm now assuming that a spindle fault perhaps took out the original VFD?

I'm controlling the spindle speed manually with a 10k pot that I've connected up to the VFD, I can get the spindle to turn very, very slowly (without tripping) with the pot at its lowest speed setting but if I turn the pot just a degree or two the VFD goes into an error condition 'overload'....I've checked the VFD settings for tripping out (they're all at default...and nothing seems untoward there)

I don't suppose it's easy to test these water cooled spindles? (I'm seeing just a couple of ohms between pins ...also when the spindle is turning even ridiculously slow, the spindle outer chassis gets warm (not ouch warm, but warm...which is surprising bearing in mind it's turning very slowly ....like 60RPM or so)

Any ideas?

[Jonathan]

VFD will trip on over current or over voltage. If the spindle is getting hot with no load, that means the current is too high. For there to be too high a current the voltage the VFD is applying must be too high (ohms law), so check what the voltage is at rpm.

The vfd, when using vf control, should increase the voltage proportional to the frequency, so (generally) rated voltage at rated speed, half voltage at half speed etc.. What might be happening is the voltage/frequency curve is set wrong, so it's applying much too high a voltage, which in turn causes too much current to flow, so the VFD trips.

[Boyan Silyavski]

Possibly as suggested by Jonathan, wrong programming of the VFD. Its a very long manual, i know. But is unavoidable. Follow it step by step.

Check the phases on the motor! Wait for the VFD untill the led goes out after disconnecting before you touch anything!

The spindle can work hours without water without heating.

You don't need a pot right now. The button on the VFD rotates and you change the frequency.

Read the manual. the VFD stores last trips, you can go there and check what happened exactly, so no need to measure anything. During operation you can also monitor A, V and so on calling them on the display with a button.

[HankMcSpank]

well, I've had a bit more dabble with some of the VFD parameters. I found the base frequency voltage setting (which was set to 230V ...Im assuming this is the max peak to peak height of the pulse train that the VFD puts out?)

Anyway, I set it low (right down to 60V)....but the VFD is still tripping with an overload condition (& I noticed a peeeoooo space invader type sound eminating from the inside spindle itself just before the VFD trips, but this might be the VFD shutting down causing that sound).

there's surprisingly little info out there about typical winding arranbgement & readings for these spindles (like I say I was reading 3 ohms between pins which seems stupidly low, cos if my calculations are correct DC output of 230V, will yield an RMS Voltage of 84V which infers 28Amps!! (but there again, I could have all this wrong!).

Also, back to the spindle internals....does anyone have a link to a diagram of the typical coil arrangement inside?

I'm 80% certain it's the spindle...begs the question has anyone upgraded & got an 800W water cooled spindle lying around they wanna sell?!

Read the manual. the VFD stores last trips, you can go there and check what happened exactly, so no need to measure anything. During operation you can also monitor A, V and so on calling them on the display with a button.

Alas, the menu structure, naming convention (& indeed the manual itself), is anything but intuitive!

[Jonathan]

Just the base frequency setting isn't what you need, as that's the voltage at the rated frequency (400Hz), but we need to know the voltage across the whole range. Have you checked that the frequency this voltage refers to is definately 400Hz, as if it's 50Hz that would explain what's causing the problem, as it means the VFD is applying 8 times the required voltage at 50Hz.

You're correct in saying that a DC output of 230V would imply a very high current (although it's not 230V DC, 84V or even 28A), but fortunately the VFD outputs AC not DC! The impedance of the spindle increases with the frequency applied. You can think of impedance as resistance, but for an AC circuit with inductors/capacitors. So at 0Hz (DC) the impedance is equal to the DC resistance you measured (3 ohms, which sounds about right), but as soon as you increase the frequency the impedance increases proportionately. It also changes with load. That's why as the frequency increases you need to apply a higher voltage to be able to output the same torque. So in short your measurement implies that the winding's aren't burn out, but it's nowhere near enough to say if the spindle will work.

Alas, the menu structure, naming convention (& indeed the manual itself), is anything but intuitive!

Strangely the translated chinese manual for the VFDs most people get to control their spindles are easy to understand.

Have you got skype? If you're sitting there with the VFD we can probably sort this out in half an hour...

[Jonathan]

Didn't spot this bit...

Also, back to the spindle internals....does anyone have a link to a diagram of the typical coil arrangement inside?

It'll be one of these:



Just to be clear, you did check that the 3 resistances are the same? If off by more than about 10% (complete guess) then you've got a problem.

[HankMcSpank]

You're correct in saying that a DC output of 230V would imply a very high current (although it's not 230V DC, 84V or even 28A), but fortunately the VFD outputs AC not DC.

I did some speed research earlier...my interpretation may be incorrect, but I thought these VFDs put out a PWM pulse stream (& relies on the inductance of the spindle coils to essentially filter the VFD output pulses & restore a sine wave from them - similar to filterless class D audio amplifiers). If that the case, then the aforementioned 230V output, will be the maximum peak to peak level of the restored sine wave)

Have you got skype? If you're sitting there with the VFD we can probably sort this out in half an hour...

I have skype, which I seldom use & I can't immediately lay my hands on my webcam - if I find it I'll give you a shout on here :-) (but missus has furrowed brow which roughly translates into "you must not pursue this anymore this evening!")

My VFD manual is here...

http://www.mototecnica.eu/ebay/Inver...ng%20VFNC3.PDF (great for sleep inducement at this time of night!)