Any electronics experts here?

[Anonymous]

I am a bit concerned about my bandsaw motor. I was doing some repeat profiling on the bandsaw today and hence had it running continuously for about half an hour albeit with very little load. After I had finished I was cleaning up and noticed a hot electrics smell. The motor had become too hot to touch. It had become so hot I think it split the attached plastic casing that houses the (capacitor?). Although I cannot say for sure but I hadn't noticed it was split before. On opening this casing there seemed to be a little oily moisture on the plastic.
On further investigation it seems that when it is running the air from the motor fan across the fins manages to keep it cool but on stopping it begins to get hotter and hotter.
Do you think something could be wrong.
Its a Startrite 351SE that I've had for about three months and this is the first lengthy run it has had.
I've also posted on usenet in uk-diy but thought there'd be more bandsaw experience on this forum. I'd be interested in Kityuser's comments as I believe he has recently aquired a 351SE.

Thanks

Roy

 

[Midnight]

Roy... it's unusual for an induction motor not to be capable of handling the kinda loads you're talking about; driving a bandsaw should be the last thing that makes it so hot. Something's wayyyyyy wrong; too much resistance somewhere, and, provided everything's healthy, it shouldn't be electrical resistance.
At only 3 months old... this one needs to go back to the supplier or manufacturer; the heat's probably toasted the cap.. you'll know about it if it "goes"... a cap that size does a damn good impression of a hand grenade...

As for the cause... I'm guessing here... but I'd be looking for excessive mechanical resistance... dry motor bearings, dry pulley bearings, blade tension??. It'll be something basic...

 

[Adam]

Some capacitors use oil as the dilectric, that is, - the insulator between the thin film of metal, which normally gets rolled up into a tube and forms the normal cyclindrical shape you see capacitors in. Over a period of time, it is possible for the oil to evaporate, and in these circumstances, pass a high current - possibly causing it to split. I'd almost certainly recommend it needs replacing, *insert normal "use an electrician if you feel unsure", although its normally just a case of unscrewing, and putting a new one on, and joining the wires back on. Can you give the manufacturer a ring?

I've no direct experince of this on motors, I have seen it on Hi-Fi speakers, which have been stood in front of a radiator, or too close to a fire.

Adam

 

[Anonymous]

Roy

The capacitor on your motor is most likely an electrolytic type as these are commonly designed not to break down at mains voltages. When they do finally fail, the dialectric emerges as a sort of goo. However, they usually go pretty quickly and one would not expect a prolonged leakage. If the cap is leaking, then there will be a point when the motor ceases to run and the cap is deceased - may end with a little 'pop'.
Dieing capacitor will smell of electrical burning.

The motor will get hotter when stopped as the fan only cools the outer fins and outside of the casing. As the motor stands, the heat from inside conducts through the shell to the outsoide without the forced cooling to remove it.

Your motor should not get too hot to touch.

I would suggest taking the rear cover off and ensure tha tthe fan is firmly attached to the shaft and thus spinning at full motor speed when running. Do NOT run the motor with the rear cover off as it is dangerous AND no air will flow down the motor to cool it - these motors rely on the motor shroud to divert air along the fins.


Tony

 

[kityuser]

I indeed ended up with a 351E, but as of yet have not had it running (see previous thread).

talking with the shop where the saw was purchased we think the electronic brake may be stuck on (?)

the "electrical" smell that you describe is usually OZONE, and can be generated by arching electricity breaking the air down (sometimes smell it on trains as well). But this smell is usually associated with DC motors that have brushes (or the strange ac motor that still has brushes and is used in routers).

as previously stated, motors should`nt get "too hot to touch"

 

[Newbie_Neil]

Hi Roy

As you've only had it three months, and it's still under warranty, I would go back to the company you bought it from and ask them to resolve it for you. Failing that you should contact Record Power on 0870 770 1777

Cheers
Neil

 

[Anonymous]

Thanks everyone.

I didn't notice Kityuser's thread "Startrite problems please help" when I started this one and I will now post news of today's developments in that thread.

Roy