800w spindle - noise & controlling remotely

[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!)

[Jonathan]

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)

Yes the VFD outputs a PWM signal which is subsequently filtered by the inductance of the spindle, but there's a bit more to it. The input to the VFD is the mains, which is simply rectified and stored in some capacitors - this is called the DC bus. The DC bus voltage is therefore around 230*1.414.. =325V DC, so the peak voltage of the PWM waveform outputted will be around 325VDC. That means the rms output voltage will be 325/1.414=230V AC. Other things do influence the DC-bus voltage and your drive can do more than use a simple PWM signal with vf control to change things, but that's not important right now...

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!")

Don't need a webcam.

[richie00boy]

Just measured my spindle and I've got 4.4 ohms between phases. When driven by AC or pulses the impedance seen is higher because of the inductance, so you can't just use simple ohms law to work out the current.

[HankMcSpank]

Just measured my spindle and I've got 4.4 ohms between phases. When driven by AC or pulses the impedance seen is higher because of the inductance, so you can't just use simple ohms law to work out the current.

Thanks for that ...I'm measuring 3.5 ohms between all phases. (it was late & I'd been onto this all day...& with the benefit of a good nights kip, I now fully realise that my head was fogged!)