Monitoring temperature

Conradconrad

What are the differences between

1) monitoring temperature at the brushes such as with a N.O. (Normally Open) thermostat in the motor brush mechanism. The kind where the thermostat will close (like a switch) when the temperature gets too high.

2) External case temperature? As with a laser gun or even placing one of these probes on the case and mounting the display on the dash so you can see real time temps?
http://www.ebay.com/itm/3m-12V-Blue-...id=p5731.m3795

Is there also a difference in temperature values captured from 1 vs 2?

BGW

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yurtle

In industrial motors the sensors are embedded in the windings and bearings. RTDs, thermistors, or switches are used. Several can track trends, while others are simple preset on/off switches.

I've not seen any offered in standard buggy motors.

Conradconrad

EMP is able to install(into a motor they are buidling for me) a N.O. thermostat switch that I can connect to a light or a buzzer.
Trips at 140 degrees Celsius.

I was planning on attaching the probe the option 2 (link to ebay) to the motor case and watching the temps real time like that.

In my opinion this data would allow me to see the temperature rising and adjust accordingly. Whereas once the thermostat trips it would still be precautionary but I would no know in advance until it trips.

yurtle

A NO Thermostat sounds like it would not be able to track trends, but simply tell you when it's reached a set-point. What temperature would the thermostat be set for? Ask them if they could install a real temp sensor, like an RTD, so you can have an actual reading, and not just a switch. You want an analog signal, not discrete.

Conradconrad

The thermostat is a switch that will close at 140 deg centigrade

From EMP-

Common insulation classes are A, B, F, and H, although others exist. Most golf car motors are class B, F, and H. Most of what EMP builds is actually class H

Class H is higher temperature yet and could survive up to 180 C (356 F). Now, this is the temperature around the windings and current carrying components, so you would not expect the exterior of the motor to also be at this temperature. The difficulty is that there is not any perfect correlation between the temperature on the outside of a motor and the temperature at the windings and brushes could be much higher. If a motor is in a really controlled environment where the amps and ambient temperature are constant, there would eventually be a pretty decent understanding of the difference in temperature between the outside of a motor and the insides.

So, is 200 F on the outside too hot? That depends. You could get a motor and beat the heck out of it, burning out the guts before the guts before the heat ever stabilizes on the outside of the motor at 200 F. On the other hand, if the duty is more consistent 200 F on the outside may only mean 250 F on the inside.

For a fan motor in a warehouse or some motor that has pretty constant duty, understanding external temperature can often be OK. Unfortunately, golf car motors usually have much more random use. You will start up with amp levels 10x the rated amp level and then level off, stop again, accelerate some, speed up, slow down, climb a hill, go down a hill. In that kind of case, the best temperature to be aware of are internal temperatures in the area of the motor most likely to get hot. In a DC motor, this is usually (not always) the brush system. For that reason, most motors shipped from EMP with thermostats have them mounted right on the brush mechanism.

EXTERNAL TEMPERATURE MEASUREMENT
Is it bad? It is certainly better than nothing, but it would never be as good as measuring temperature on the area most likely to overheat first. If you are smart enough to at least want to monitor temperature, you are probably smart enough to know when you are doing something too aggressive in the first place.

THERMOSTAT
For now, EMP only offers thermostats. These are devices that click open or closed when a temperature is met. People have used them to power warning lights and buzzers and even very small fans. Maybe someday we will get fancier and install thermistors or thermocouples where actual temperature would be presented, rather than just a sudden warning that you are too hot.

Great information from Chuck.

I think the other options as you have mentioned may increase cost.

I will be running both.

EMP N.O. thermostat to a light, maybe even a light with buzzer combo if I can find one?

And external mount probe attached to case(not sure how just yet). Since its so cheap and the one I linked above has a 3 meter probe cable length- should be easy to run from dash to motor.

Ill put each side by side

scottyb

I love it I had to laugh at :
EXTERNAL TEMPERATURE MEASUREMENT
Is it bad? It is certainly better than nothing, but it would never be as good as measuring temperature on the area most likely to overheat first. If you are smart enough to at least want to monitor temperature, you are probably smart enough to know when you are doing something too aggressive in the first place.

I did some experimenting and ended up with this inexpensive monitor:
I use 150º case temp as my outside max mainly because when shut off the 150º shoots up to 170º - 180º easy and 200º is a number I want to stay under.

See post 43 > http://www.buggiesgonewild.com/elect...p-exist-5.html


It would be really interesting to do both. I may have to send EMP a motor.

yurtle

Again, this is a NO switch, not a true monitor. If you're gonna pay for a device embedded in the windings, do what industry does and install a true analog sensor, so you will know more than "not too hot - too hot".

mjroman20

A switch type option would allow you to connect a mode change switch too depending on what controller is being used. Say put the controller into a current cutback to give it a chance to cool off.

From what I have read the real concern is the field winding temp. If measuring on the case rather than right inside the windings you just need to take into account the difference through the housing, probably around 10~20C.

scottyb

Yes as stated, I use 150º outside case at the shoe mount bolt as my guide. My object was to below 200º internal after the the motor was shut down and temperature rose 20º as it did in my experiments.

yurtle

I assume you mean °F?