Broken spindle motor or drive or fuse? Advice please

[el$syd]

Hi,
OOPS my Triac PC spindle drive is broken - my fault - drove the mill to a zero point which was through 50mm of aluminium!

Stopped the mill before it got very far but then the spindle would not restart, Forward or Reverse (M3 or M4) - the emergency stop came on and I had to use the override switch to home the XYZ.
I hope I have only blown a fuse somewhere (apart from my own) - but all the fuses I can see seem to check out OK.
Is there another fuse somewhere else that I am missing? I notice on the TRIAC drawing sheet 1 fuse S1 - where is it please?
Could I have done more serious damage? Burnt out the motor driver or even the motor?
What is the best way to test this?

many thanks -

[Martin]

There are 2 spindle drive fuses fitted to the Traiac PC.

Both are marked up as fuse F1

There should be a 1 1/4" 15amp or 16 amp ceramic fuse on the spindle drive board.
There should be a 20 mm 10 amp fuse mounted next to the terrminals. You need to unscrew the black cap to remove the fuse.

Either or both may have blown.

[el$syd]

Thanks for your help - I have tested the fuse on the Sprint 1200 spindle board and it is OK.
However I cannot find the other fuse you mentioned... There is no black cap near the board terminals as far as I can see. Which terminals are you referring to?
The TRIAC is 1995 vintage. I have tested all the other fuses and they are OK. The relays click in and out with M3,M4 and M5.
At the motor connector there is 24V wrt gnd on both the field coil so the pd between them is 0v, and there is -70V wrt 0v on both the armature connections so again the pd is 0v for the armature. Both the tacho connections read -70v wrt ground to.
The spindle ON LED is on and the STALL light is off.

[Martin]

If the power LED on the sprint 1200 drive is lit then both fusess must be correct.

The best way to go from here is to set the spindle to run at say 2000rpm.

Check the mains on terminals 12 & 13. You should have 240volts AC.
Check the analogue on terminals 2 & 3. You should have around 5volts DC.
Check the aramature output on terminals 8 & 9. You should be looking for somwhere around 100volts DC. If you are getting a voltage at this point then there is a problem with the motor. Remove the motor cover & check for voltage at the connection block. Check the motor brushess.
Link out the run command on terminals 4 & 5.

Hopefully it should make more sense.

[el$syd]

Hi thanks for the information - these are the results :

Check the mains on terminals 12 & 13. You should have 240volts AC. answer 63V
Check the analogue on terminals 2 & 3. You should have around 5volts DC. answer 2 V
Check the armature output on terminals 8 & 9. answer 0V

So it looks like I have a supply problem from somewhere - the intriguing thing is that the Sprint 1200 ON led is lit, perhaps it doesn't need much to light it?

[Denford Admin]

Check the mains on terminals 12 & 13. You should have 240volts AC. answer 63V

If you remove the wires and put them into a connector block, do they now read 240?
(Obviously power off 1st and take a note of what wire goes where)

[el$syd]

Yes - as you suspected, when I remove the live mains wire from the connector and measure the voltage it is 230V.
Does that mean the board is blown?

I also measured the motor as follows:
Armature A1-A2 0 ohms
Field K1-K2 0 ohms
Tacho T1-T22 40 ohms

Accuracy of the meter at these low levels is suspect though....

[Denford Admin]

I would suspect a drive component has gone then...I can't really see what damage driving into the block would have done to the armature or field (unless wires have snapped or brushes broken). I'd inspect everything closely now for signs of damage-hopefully it will be just need a thyristor replacing/

[Martin]

I can't see why you are only getting 63V on 12 & 13 when connected.

It may be worth checking the wires all the way back to make sure they are tight at all the connections.

[el$syd]

Has anyone experience of changing the Thyristors? is it a big job?
And does anyone know what type they are?
Or should I get a new card?

MANY THANKS

[Steve]

I would recheck the voltage readings first.

I do not see how you could get 240V on the wires and 63V when plugged in.

If somthing caused that voltdrop then there would be a big bang!

The fuse would blow and you would have 0V.

I would recheck the connections and remeasure.

[el$syd]

Removed motor and stripped it - it is fine.
Looked at what are supposed to be field coils - a couple of wires going to one of the brushes.
The motor is a permanent magnet motor and does not need a field coil - so what does the field coil connection which feeds back to the Sprint card actually do?
Can it be left open circuit?
Is it a thermal cutout?
Once we had established the motor was PM we ran it with a 12V battery on the armature and it turns OK.
Sprint card still reads the same as before i.e. 63 V from the AC supply connectors when connected and 230V when o/c.

[Steve]

You are probably talking about the tacho feedback winding.

This feedsback to the sprint to let it know the speed and allows it to compensate if the spindle starts to slow down.

[Steve]

I attach a page from the triac PC scematic. Where are you measuring 63 Volts

[Steve]

Also found this diagram.

[el$syd]

Thanks for these drawings.
The mains I am trying to measure is on the SPRINT 1200 board between pins 12 and 13, labelled N and L on the circuit diagram from the Sprint 1200 Manual.
There are 6 connections on the motor:
The top 2, T1 and T2 are the Tachometer - they go to a small set of brushes on a separate armature at the top of the motor.
The middle connections are K1 and K2 - labelled field coil on the SPRINT board, they go to wires ending under one of the main motor's brushes.
The bottom 2 connections A1 and A2 go to the 4 brushes for the motor.

If I remove K1 and K2 then I get an emergency stop and everything stops. If I put them back in the emergency stop disappears.
So am puzzled by what K1 and K2 are, they are not field coils as the motor runs OK with 12v on the armature connections and no other connections.

Removing K1 and K2 from the motor and putting a 220 ohm resistor across the wires going back to the SPRINT board 'removes' the emergency stop signal.... Page 7 section 18 of the SPRINT manual states that the field coil should be a couple of hundred ohms, K1 and K2 on the motor are 0 ohm.

[Martin]

K1 & K2 is a thermal in case the motor overheats. It is as you say part of the E-Stop line.

[el$syd]

Thanks for that confirmation.
Should the thermal overload sensor be closed circuit when normal and open when overheated?
If that is so - would I have blown the thyristors or diodes on the board?

Many thanks for your help - much appreciated.

[Martin]

It should be closed circuit when normal & open when overheated.
It feeds straight in to the E-Stop line so it will not have caused any issues.

It does sound like we are back round to the spindle drive. It just seems strange that you get a voltage drop down to 63volts.

[el$syd]

Thank you, excellent. That reassures me that I did not damage the motor after all. I will now concentrate my efforts around the Thyristors /SCRs and see whether they are damaged.
Or buy a new board...