Hi All,

I am far from an expert, and i was hoping one of you experts can help me.

I building a electric dirt bike, the motor installed is a 24V 500W 27.4A DC Brush Motor. I am installing a Temperature Gauge that contains a sensor and was curious where would I take my measurement to have the most effective results.
1.Motor Front Cap
2.Motor Rear Cap
3. Motor Body

Thank you All

Eddie

 

Generally a thermal sensor is embedded or attached to the stator.
With a DC brushed motor the heat originates from the armature and then radiates out to the stator, if you sense too high, by the time the heat has radiated to the stator, the armature can have cooked.
Max.

 

Take a look at any self-ventilation of the motor. I would lean towards putting the sensor on the downstream end of any airflow pattern, so that a temperature rise shows up sooner. I'd look for a spot where the sensor is protected and accessible if you need to get at the connections or replace the sensor.

 

Hi

Thank you so much for all the inputs, The motor definitely does not have any kind of sensor mounted to the stator or inside. Ive searched many sites trying to find a decent Temperature Sensor to mount.
The temperature is to measure a ballpark reading so my nephew does blow up the motor.
From reading the response it sounds like to mount the sensor towards the back plate and body. I have attached a pic of the motor I am referring too.

 

I would not mount it to the end plate, if you go by small sealed fan motors etc, the sensor is embedded between winding's, as they are going to be the recipients of radiated heat from the rotor.
There are slim plastic sleeve type for this method , the other type have a plate with mounting screws.
The other way is to mount an external time delay fuse.
Max.

 

Hi Max

Do you have a link that you are referring to ?

 

I just bought one a couple of months ago and cannot find the link, but if you Google 'Bi-metal winding sensor'.
You will find lots of hits.
The screw on type are used in dryers etc, but are a little larger than the embedded type.
https://www.indiamart.com/ravirajprocesscontrols/resistance-temperature-detectors-for-bearings.html
Max.

 

Max

I apologize for the back and forth, it seems I am not getting it. When i look up Bi-Metal Winding Sensor it seems these are sensor that mount internally but i can be mistaken.

This is what I have I was curious if I can get this work.

 

I would not consider that the best solution, you would need to mount it along the stator to do any good.
The problem is to ensure the right contact and a circular sensor is not the best for that.
I think the fusing method may be the better choice. Say 25amp, or 20a to start with.
Max.

 

Max

I know the sensor mounted on the body is not the best solution, again all i want is a ball park temperature reading.

I'm sorry I really do not understand, when you mentioned fusing method.

 

The rated current is 27.4amps, this is most likely the continuous rated current, for intermediate use it would be higher for a short period, a time delay fuse could be rated for the continuous current or just below.
Max.

 

Your opening statement refers to experts. I guess that lets me out of this discussion. HOWEVER, I'm willing to bet there's a fusible link inside the motor already. It's a fuse of sorts that burns out when an over temperature condition is met. Burning this motor out may be no greater than just burning out the fusible link. Wherever it is located, if you are able to access it and determine its rating you can then have a better idea of how much heat the motor can stand without burning out the fusible link. And that's probably the same location you'd want to mount your temperature sensor. Some sort of thermal epoxy (if there is such a thing) to make sure any heat built up in the motor is quickly transferred to the sensor. If you're good with your beans you can make an automatic shutdown switch that kills electric power to the motor. And can only be restored by use of a reset button OR an automatic reset when things cool down enough.

Look on your refrigerator compressor. There's a thermal switch mounted on its side. If it overheats the motor shuts down. Doesn't attempt to start again until the motor has cooled sufficiently. If the motor is frozen then the motor may eventually self destruct from repeated attempts to start. But the fridge doesn't erupt in flames. The solution to your problem may be as simple as installing one of these thermal switches, one rated to open before your fusible link blows. Then your nephew can ride till the thermal switch pops open. When it cools down it will re-engage, and he can ride again. But shouldn't. Not until the motor has had sufficient time to cool. And you may want to rethink your gearing of the motor. Perhaps you're overloading it. Or if someone too heavy is trying to ride it - you need to shut things down quickly and reliably.

Nuff from the peanut gallery. I'm NOT the expert you're looking for.

 

The experts are raising a good point. Reading what the temperature is is one thing, taking action is another. And having a readout doesn't guarantee action nearly as well as the high-temp cutouts in modern appliances.

My brother new a girl in high school that got a sports car from daddy. She drove it until the oil pressure gauge read empty and then pulled in for a refill. Daddy had to buy her a second one. She proceeded to do the same thing. Not sure if she was blond.

 

Wayne: Did you see the episode of "Home Improvements" (with Tim Allen)? Jill was driving the Nomad with the oil light on. She was concerned but did nothing. When Tim found out about it he was furious. She said "I thought it would get brighter if the problem got worse."

Always wished there was a knob on the TV you could turn up the intelligence. There's one marked "Brightness" but it don't work.

 

The ones I linked to in post #7 are common in fan motors etc, these just open when the temperature is exceeded, close again when cooled.
The motor shown is a cheaper Chinese motor, they do not have any internal thermal protection.
Max.

 

To me, a digital readout would seem like a way to measure my ability to abuse the bike. I would try breaking my previous record each day until I have to call my uncle to see if he'll come over and help me fix my bike.

 

Hi All

Correct these motor do not have a Internal Thermal Protection. I did add a reset-able circuit breaker to the motor of 30amps.

Just wanted the temperature gauge for riding in dirt or grass, need to explain to my nephew no guarantees on the dirt bike.

 

Hi All

Correct these motor do not have a Internal Thermal Protection. I did add a reset-able circuit breaker to the motor of 30amps.

Just wanted the temperature gauge for riding in dirt or grass, need to explain to my nephew no guarantees on the dirt bike.

You might want to put a temp monitor on the battery too. Failure of the battery could be more physically dangerous to your nephew than the motor overheating.