Possible problem with Jaguar Cub Inverter.

[Eric the chicken]

I have titled this thread as 'possible' problem as I'm not too sure whether it's the inverter or the motor. The inverter was bought in April 2011 to run my newly acquired Colchester Student. The lathe, when I bought it was fitted with a three phase motor. The old motor turned its toes up in 2014 and I bought a new one and until recently everything has been fine with the lathe. That was until recently, I turned the lathe on and the motor laboured and turned very slowly.

To show the pattern of use. I don't use the lathe every day by any means. Sometimes I may not use it for a couple of weeks, other times a couple of times a week. So as far as I'm concerned the motor I fitted in 2014 has not had a huge amount of use.

As the inverter was easier to access I spoke to a very helpful chap a the place that I bought the inverter from and he ran through a sequence of checks with me and said that he thought the inverter was OK. I than decided I'd have to bite the bullet and remove the motor from the lathe to check it. I removed the motor and with it on the bench checked the resistance between windings and all were 1.8 ohms. I must emphasise I am not an electrician but according to what I've read the figures I've got would appear to indicate that the motor is OK. In addition the motor spins easily by hand and feels smooth as it turns. The motor is clean and not showing any physical damage.

I'm now fairly certain that the problem must lie with inverter, and this is where I need to ask the forum, does anyone have experience of problems with this particular model of inverter? It's an IMO Jaguar Cub VXR. As I said previously I'm not an electrician and as far as electronics is concerned I don't have clue. Any suggestions welcomed. A suggestion as to a competent repairer would also be welcomed.
















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[Hopefuldave]

Does the motor on the bench (or with the belts off) running from the inverter spin up normally? Have you checked that there's not an issue with the lathe (rather than motor and VFD)?
Possibility that the VFD has lost settings, e.g. the max current setting - if this is the case it'll try to spin the motor up (and probably will without the load of the lathe, e.g. belts off) but bog down with a load - I'm not familiar withthe Jag Cub, does it display fault codes when the motor's trying to run?

 

[Eric the chicken]

Thanks for your quick response. After I took the motor off the lathe, without the drive belt attached, I connected it to the inverter, the motor turned very slowly, at a guess 5 to 10 rpm. Inverter fault codes I'm going to have to look into, as I said electronics is not something I know anything about, although I see a steep learning curve in the near future

 

[Slowcoach]

Re-Nu on murdock road might test the motor or the vfd too.
I just wandered in their workshop (couldn’t really find a reception type door) and asked about them about looking at a 3 phase motor with no plate on and they seemed helpful. I havent got round to going back yet.

 

[Eric the chicken]

Thanks for that, I think I'll pursue the fault code route with inverter, but getting the motor checked would prove that it was OK.

 

[500e]

Mates student runs a Jaguar cub, has built a traction engine with no problems, been on there 8/10
years.
Cant get the setup as he has taken to the booze and I have fallen out with him

 

[Agroshield]

Does it turn slowly for as long as you leave it switched on (i.e. 5-10 minutes running) or does it fault out?

Any coolant pump on the machine? Wire it up to the VFD and if it works OK, it is not the VFD.

If it too turns very slowly, it could be a parameter issue (e.g. it has somehow decided that 10Hz is the maximum it wants to give out).

If no pump, in principle, try the VFD with another motor.

 

[Eric the chicken]

Once again thanks for spending time to answer. I've not left the motor running at the slow speed for any appreciable time as it so obviously struggling I don't want to cause any damage. The lathe has a coolant pump which I never use,( I apply cutting fluid with a brush.) I'll wire up the coolant pump and see what happens. As far a second motor is concerned I've only got the one three phase motor. I have a mate whose son has a workshop with three phase so one plan is to take the motor to him and check it out.

 

[Eric the chicken]

This afternoon's effort with the motor. As previously stated. The motor is on the floor beside the lathe but still connected to the inverter. With power on multimeter readings between the three phases build to approximately 60-64 volts then drop back and then build back to 60-64 volts this happens constantly and consistently the motor is turning at about an estimated 10 to 20 rpm. The voltage is unaffected by altering the speed control on the inverter. I have still to check the fault codes on the inverter. I thought best to eliminate on problem at a time. I want to confirm that the motor is OK before moving on to the inverter.

 

[Chippie]

It’s conceivable that you don’t have an undervoltage condition, else there would be a fault code locking the inverter up. But if you could check the dc bus voltage it would help. Also any fault codes…
The fact that the speed control has no effect on the voltage to the motor would indicate either a fault or the inverter has defaulted to a fixed speed?
As you say, really need to eliminate the motor as a fault cause, use the coolant pump? ….then move on to the inverter