Roger, Thanks, This is more than enough information. I like the idea of drilling and epoxy into place one brush in each motor. I just looked, there are two brushes in each of four places. Eight brushes on each motor. I am thinking I will thermocouple the brush closest to the armature as it should be the hotter of the two.
Thanks for the quick reply. Mark Subject: Re: [EVDL] temp sensors on brushes Mark Grasser wrote: > I seem to remember one of the hottest points being the brushes themselves. > I am going to drill and tap about ΒΌ" deep for 4-40 screw on the wire > end of the brush. Concerns would be these: are the brushes a god > point to read temperature? Am I in danger of splitting the brush > during this process? > Will the screw threads hold up? Would I be smarter attempting to epoxy > the thermistor to the brush instead? Oh, What temperatures should I > expect? Convention appears to be to epoxy a thermocouple into the brush for monitoring brush temperatures. The positive brushes tend to run hotter, so if you only monitor one, make it a positive one. Jim Husted noted that there are downsides to attaching a temperature sensor to the brush, including the possibility of the sensor wiring becoming connected to the traction power, the sensor wiring interfering with free movement of the brush (e.g. most thermocouple wire is relatively stiff solid core), and that you have to redo the sensor when you replace the brushes. He suggested the mounting the sensor to the brush holder might be a reasonable compromise. Below are a couple of relevant posts from those more knowledgeable than I on this subject. Cheers, Roger. > -----Original Message----- > From: Otmar [mailto:[email protected]] > Sent: July-24-05 5:54 PM > To: [email protected] > Subject: Re: Thermocouple position, was: Re: 120v 6.7" ADC? > > At 9:17 PM +1000 7/14/05, James Massey wrote: > >Hi Otmar and all > > > >At 10:37 AM 12/07/05 -0700, Otmar wrote: > >>I was taught by the engineers at ADC to drill a half inch deep hole > >>in the positive brush and put the thermocouple in there. > > > >Any ideas as to why the positive brush? > > > >Is it just an ADC in-house convention, or is there a technical reason > >for > it? > > > >I can theorise no reason for the positive brush to get hotter than > >the negative, unless the electron flow into the brush heats it more > >than the electron flow out of the negative one. > > > >Any theories? > > Sorry for the delay, I've been out of town and am just getting to > hundreds of EV list messages. > > > I was told the positive brush gets hotter. I can only theorize that it > has to do with electron flow. > > -- > -Otmar- > -----Original Message----- > From: [email protected] [mailto:[email protected]] > On Behalf Of Jeff Major > Sent: June-19-07 10:42 AM > To: [email protected] > Subject: Re: Max motor temperatures and temp sender install > > > Hi Mark, Richard, > > Class H insulation is 180 degree C. Meaning at 180C, insulation will > last 10,000 hours(or half life of 10,000). It depends where the > thermal sensor is located in the motor. Cannot be in the armature, > that is hard to do because it rotates. So, I'm guessing, it is in the > field coil. Now it depends on the motor design, but the ones I worked > with years ago, would, on the one hour temp rise test, have the > armature reach rated temp first. So there would be a differential > between the arm and field coil temps. > The temp sensor would be selected to that field coil temp which > related to arm temp limit. So the assumption would be that when your > temp sensor trips, the hottest part of the motor is at limit. > > Having a 120C temp would indicate that you should back off or end the > trip soon, probably not stop at the side of the road and wait for the > motor to cool down. > You might also add forced air cooling if you find the temp light > coming on often. > > As for motor temperature in general, at the end of thermal rating > tests I used to run, it was not uncommon to have the outside of the > motor frame at 100C. As for the brushes, we used to install > thermocouples in the brush by carefully drilling a hole in the top of > the brush, insulating the TC with epoxy and then insterting the TC > into the epoxy filled hole. On short time based thermal runs, like 5 > or 10 minutes or shorter, the brush would be the limiting temperature > for the motor. This was allowed to reach > 200 degree C as the internal brush temperature where no insulation is > present. The outside of the brush would be lower where the pigtails > and springs are. > > So, for a field coil temp limit, 120 to 140C sounds good to me. On > the brush, I'd say 180C, hopefully that would be just peaks on the > brush, like at the top of a hill, and the average would be 40 or 50 > lower. > > My experience was back in the good old days, so I don't really know > how they design those new motors. > Hope that helps. > > Jeff _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
