V2XT: Spindle Enable dead fault.

[9 1/2]

Hey group. I'm having an on going problem with my unit that I'm unable
to figure out.

First some info: 1999 V2XT DX32 unit. completely original and being
run with 3 ph power VIA 3hp Hitachi VFD.

Unit powers up no problem, all axes home smoothly. I can jog and
locate the table just fine. The issue starts when I try to enable the
spindle.
The VFD (drive) registers current over load and trips out the safety
(like a braker would do) no damage is done.

So in an effort to source the overload here is what I've done so far.
I started with checking continuity on all the "enable" "start" "hi"
"lo" momentary switches and harness. All checked out normal. no dead
shorts to each other, no dead shorts to the chassis.

I then disconnected the leads to the motor itself and did the same
continuity test to all three leads (L1-L2-L3) with normal readings
(this was done with both ends disconnected from the machine checking
cross shorts and dead shorts)

So in an effort to remove the "Is-the-motor-fried" variable I then
powered it (the motor) up via direct feed from the VFD (controlling
start / stop / accel via the vfd control panel) This proved the motor
sound and smooth and the spindle not seized.

FINALLY I then powered up the mill with the motor left disconnected.
The enable procedure went fine with the screen showing "spindle HI"
Not soon after I notice the familiar smell of starting to melt / burn
wire or electrical component (that smell we all dread, secondly only
the seeing the "magic smoke" let out)

any suggestions why the vfd would dead fault only when the motor is
connected and where should I continue to hunt for my issue? Any
possibility the contactors are stuck closed? Can they be cleaned like
an electrical fuel pump contactor?

I'd be deeply in debt to any one that kicks me in the right direction.

Peace

[9 1/2]

update:

I've been looking at the params on the Hitachi, SJ-200 nfu22, and tuned the amperage overload settings. I set it all the way up to 120% of drive rating (max. allowable) and still had an issue. It was then I realized the combined amperage draw of the V2XT machine was 20a and the most my drive will output is 12 amps (at120% over amp setting)
This leads me to believe the total draw is too much for the drive.
To that end I've been considering splitting out the two 120 volt legs that feed the two transformers. This way the VFD will only provide power when the spindle is called up, otherwise the rest of the system will run off 120 volt single phase power.

I've studied the schematics for a few days now (in anticipation of this issue) and feel this is my best option (rather than buying a THIRD larger vfd drive)

The transformers are taking two legs off the 3 phase power and converting it BACK to single phase 120 volts [1L1 plus 1L2 and 1L1 plus 1L3 respectively] (for the pc functions) and 100 volts DC (among other voltages like 24v etc etc) for the axis drive and motors.

does this seem like a reasonable approach?

Owen

[9 1/2]

Well I sucsessfully split out the 120 volt components by inputing 240 volt single phase power to the T1 and T2 transformers. In turn they did what ever it is they need to do allowing the drives and pc to power up and enable.

I then turned on the VFD to provide 3 phase power to the spindle contactor blocks.

Enabled the spindle and every thing worked out fine. For a while ............ then three filters located on the input side of the spindle contactor blocks began to smoke. I powered the unit down and consulted the schematic.

Does anyone the purpose of these units? do they act like a regulator to remove excess amperage? I am puzzled and so close to my goal.

[Al_The_Man]

Originally Posted by 9 1/2 FINALLY I then powered up the mill with the motor left disconnected. The enable procedure went fine with the screen showing "spindle HI" Not soon after I notice the familiar smell of starting to melt / burn wire or electrical component (that smell we all dread, secondly only the seeing the "magic smoke" let out)

I read through your posts a few times to try and get the gist of what is going on, If you have smoke/smell with the motor disconnected then you have a problem with the drive, I would say, I assume you do not have anything connected in the way of a contactor etc between the VFD and the motor?
You have 1 phase coming in to this machine? And the VFD is fed with 220~240 1 phase?
Normally it is hard to fry a VFD as it should go into current limit or shut down if short or ground problem.
Where is the spindle contactor wired in that you mention? If there is an input reactor, this is a 3 phase choke with three windings in series with each input phase, if three phase input.
Al.

[9 1/2]

Hi Al,

The source of the smoke were (was?) three items marked as "FILTER" on the schematic. They are connected down in the cabinette where the spindle contactor block is on the input side.

I've managed, through internet research, to ascertain these units are a resistor and a .1uF capacitor in series. It is used to dampen the electrical noise generated by the contactor.

so I know *what* they are & what they are for but not why they are burning.

I've now tuned the VFD down to output no more than 7 amps, enough to run the spindle motor, as this is now the only purpose of the VFD but there was no change.

[Al_The_Man]

Normally these would burn out if the voltage was exceeded either by input voltage high or a high prevalence of voltage spikes.
If they are indeed RC snubber's http://cnczone.com/forums/showthread...hlight=snubber
MOV's (voltage dependent resistors) are sometimes used in this application also,
Al.

[Ranchero50]

From experience, VFD's put out some serious spikes and weird voltages (seen over 600vdc on a 480 VFD output. Methinks without the motor hooked up the VFD output signal is running wild. Sounds like the filters are overwhelmed. I would recommend getting a rotory phase converter. My 308 draws 8.7A at idle feeding the converter.

Jamie