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Author Topic: motor caught on fire! any idea why? Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 12-17-2009 10:48 PM                        Manufacturers never think they are liable and they'll give you a thousand reasons why they are not. It's the perversity of manufacturers' escape clauses.  |  IP: Logged Gavin Lewarne Master Film Handler Posts: 278 From: Plymouth, UK Registered: Aug 2009 posted 12-18-2009 04:18 AM                     yes, the inverters and motors have seperate fuses as well as the entire circuit being on a MCB. i have removed the inverters now, and am using our old rheostats instead. give a nice soft start. i have taken th old motor to a re-winding specialist in the area (with the hopes of it being rebuilt for a spare) but alas, he said its beyond hope. Reckons the windings had a fault from manufacture given what is damaged and the nature of the charring inside.  |  IP: Logged Rick Raskin Phenomenal Film Handler Posts: 1100 From: Manassas Virginia Registered: Jan 2003 posted 12-18-2009 07:01 AM                     Given your diagnosis it appears the motor's windings may have had a internal insulation breakdown. I suspect that there was a heat related issue that caused the fault to manifest itself. I'd certainly query the manufacturer to see if there is any possibility of compensation. I had a similar experience with another type of motor that was long out of warranty. However, the manufacturer replaced the unit and wanted the carcass returned for testing.  |  IP: Logged Ian Parfrey Phenomenal Film Handler Posts: 1049 From: Imbil Australia 26 deg 27' 42.66" S 152 deg 42' 23.40" E Registered: Feb 2009 posted 12-18-2009 07:10 AM                     Are the charred windings the field or armature?  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 12-18-2009 10:15 PM                     Ian, 3 phase motors do not have windings on the armature. (In fact, other than "Universal" motors like ones used for vacuum cleaners, mixers, etc, no modern motors have true energized windings on the armature.) quote: Mark Gulbrandsen If the motor was thermally protected (internally fused) then the manufacturer may be liable. Mark the vast majority of 3-phase motors DO NOT have built-in thermal protectors. You can special order them with "winding thermostats" which require extra leads brought back to the motor controller to trip the controller's control circuit to shutdown. The thermostats don't directly interrupt power to the windings as the opening of only one thermostat would "single-phase" the motor and burn it up quickly. Gavin, it is very important that the inverter drive is correctly programmed for the motor it is controlling, the most important parameters that need to be set are incoming line voltage, motor rated operating voltage, motor current, motor nameplate frequency, motor nameplate rpm, and carrier (or PWM) frequency (6,000Hz or 8,000Hz is normal, but I have run older motors with success by setting the PWM to 4,000Hz) The total flameout should not have happened with a properly programmed drive, but a motor can still fail even with a properly set up drive (but it still would not be damaged beyond repair. )  |  IP: Logged Gavin Lewarne Master Film Handler Posts: 278 From: Plymouth, UK Registered: Aug 2009 posted 12-19-2009 09:24 AM                     im not running the inverters any more. FYI, our motors are single phase with a custom made inverter to ramp up rather than a programmable one. it was more of a "soft start" system. it was three phase into the inverter, and single phase out. But im running the old rheostats now so no problems there. The field windings were totally buggered, nothing left really but charcoal like stuff. the armature contacts were melted and the rear bearing was badly scorched (looked like the lubricant in it also caught fire). Since installing new motor, absolutely no problems and it is much cooler while running. old one used to get very toasty.  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 12-19-2009 04:07 PM                     Ah, that explains a lot. First off, since the "inverters" were a custom deal you can forget about getting any warranty claim from the motor maker. The inverters probably didn't have any type of overload protection designed in anyways, so you're much better off going back to the rheostats. Make SURE that your motors have built-in thermal overload protection (since they're single phase) to avoid a repeat performance. I would also install fuses (time-delay or "slow-blow" type) rated at or just above the motor's nameplate current.  |  IP: Logged Gavin Lewarne Master Film Handler Posts: 278 From: Plymouth, UK Registered: Aug 2009 posted 12-20-2009 11:14 AM                     yup, have already installed inline slow blow 2.5a fuses in line with the live feed going to the motor. The rheostat is also protected inline with a 5a fuse. not sure about the motors having thermal overload protection in them, doubt it considering the age of the machines they are driving. Still no problems / heat etc with new motor!  |  IP: Logged

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