# Maximum temperature of an electric motor and proper cooling system

I have found an electric motor in my home and I want to estimate how much time it can operate until its temperature becomes too high and eventually build a cooling system for it (I have seen that there are for instance many simple peltier cooling systems at fews \$, like this one).

Unfortunately I have not found the datasheet of my motor on the web. I have only the following plate data:

Obviously it is not possible to make accurate evaluations without specific data, but it is sufficient for me a help to obtain a very rough estimation.

Basically, it is an AC 230V electric motor of 160W. It is structured in this way:

The metal rod on the left is rotated by the motor (inside the metal tube on the right). The motor theoretically reaches the end and then reverses the rotation; however I do not need this function and therefore I have removed the limit switch, therefore the motor can turn clockwise or counterclockwise indefinitely (therefore ignore the information: course 300mm).

What I want to know/estimate is:

• which is the maximum temperature for this kind of device? I need only a rough estimation (like saying that for a generic Integrated Circuit we do not want to overcome 75°C). Then I may measure the temperature while using the motor and see when it reaches this critical temperature.

• does the plate data give some informations about the maximum time of operation?

• Is there a criterion for choosing the cooling system (in a rough way)? Is it a good idea to compare the power of the engine (160W) to the power flow offered by a certain cooling system?

• Will you be removing the motor from the casing? The usual way of cooling an electric motor is to put a fan on the shaft to blow air over it through a shroud. The label says it can run for 30 seconds followed by 120 seconds of being off. The manufacturer's website gives an maximum ambient temperature of 40 ℃ for similar models. Mar 12 '20 at 11:19
• I checked with a motor manufacturer about the max temperature... I was told if you can fry an egg on it then it is too hot otherwise it should be ok... Mar 12 '20 at 11:26
• I think it's going to be extremely challenging to cool this motor sufficiently. It is not designed for continuous use. Suggest looking at other motors and topologies (such as fan-cooled motor, rack-and-pinion mechanics, etc.) Mar 12 '20 at 11:48
• Solar Mike; Eggs fry at about 150F (65C). Even the cheapest motor insulation is rated for 221F maximum (105C). Your source is being extra conservative... Mar 16 '20 at 16:44
• My rule of thumb for motor temperature is that if you can't hold onto it for more than 5 seconds (~50ºC) it's too hot. Remember the internal temperature could be much higher. We don't know what kind of actual motor is inside this device - have you opened it up to see? What do you intend to use it for? Mar 16 '20 at 22:30

## That is not a motor

That is an electric linear actuator. Those are rather pricey/expensive beasts in the €300 range, and yours is a quality make. So be gentle to it and don't destroy it.

If it's rotating the shaft, that's because the other end of the shaft is supposed to be held from rotating! At that point, you will see: the shaft will move in and out.

It will never work as a motor. If you tried, the moment it hit any rotational resistance, it would start moving in/out like it's supposed to. Yes, you removed the limit stop, but that means it will spin continuously at the limit stop. The bearings are not designed for that, and it will quickly wear out.

The motor is not designed to run continuously. It's not designed to run any longer than is required for the motor to run its travel.

## The label states the duty cycle.

No more than 30 seconds on, then at least 120 seconds off.

## Get the right thing for what you need.

I don't see any way to cool this thing enough for the duty cycle you want. Peltiers don't work that well; they make far more heat than they move.

You probably want a gear-motor. You could sell this unit for enough to get a couple of gear motors. Those can be had rated for continuous operation.

Motor temperature ratings have to do with the maximum temperature RISE over ambient that the magnet wire insulation material is rated for, vs the cooling method's ability to move heat away from the windings. When a motor is designed for "intermittant duty" as it would be in a linear actuator, that means the cooling method is not really expected to perform very efficiently. Even the lowest "Class" on motor insulation, Class A, is rated for a 60C rise over a 40C ambient, plus a 5C "hot spot" for a total maximum temperature of 105C. But that is INSIDE of the winding structure, which you don't really have access to to measure it. So determining an adequate cooling system is not going to be anything you can do with any reasonable accuracy. You can use trial and error, but if you err, the consequences are that you lose this "found" motor (and waste a perfectly good linear actuator, which may be more valuable as a unit than the motor inside of it).

By the way, peltier cooling systems for motors are basically pointless. One big enough to have any reasonable effect on that motor, assuming you can also design an air flow system for it, would far exceed the cost of just buying a motor designed for what you want to accomplish.

If it were me, I would sell it on an auction site and buy a real motor...