# How much cooling does forced air provide to a DC motor?



## Jb24601 (Aug 29, 2019)

My 9” GE series wound motor has a brush cover fitted with a 2” diameter tube for forced air cooling. How much cooling does this provide? What kind of flow is necessary? Or, is it necessary at all for a daily driver? 
Thank you.


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## major (Apr 4, 2008)

Hi Jb,
How much? Tough to put a number on it. But I say it's worth it in most cases. Most things run more efficient and last longer at cooler temperatures. I don't recall an airflow number but something along the lines of an automotive heater/ventilation blower or marine bilge ventilation fan has worked well for me and others I know. Compared to self ventilation (shaft mounted fan inside the motor), forced air cooling via duct from remote blower has several advantages. Those include cleaner and dryer air through the motor and more air through the motor. The air volume from the shaft mounted fan is dependent on motor speed. Forced air is not. So forced air is much superior at low speeds, especially beneficial going uphill slowly. And after a duration of high speed/high power travel, then encountering a stop and wait in traffic, without forced ventilation, the motor will experience heat soak. The motor benefits from having this heat removed quickly by the blower.

Downsides to forced air is the space of the blower and related hardware, as well as the energy used by the blower fan. If a constant running fan is undesirable, it can be activated with a thermal sensor in/on the motor. Depends on your installation and drive cycle.
Regards,
major


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## Isaac97 (Jun 3, 2019)

I think I've heard about forced air helping the motor last longer - the brushes wear down, creating carbon dust, which sometimes gets stuck in places and causes shorts. So some air blown in there would keep everything cleaner. As long as you don't have water flying into the motor it should improve longevity a bit.


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## remy_martian (Feb 4, 2019)

That motor's rated power at elevated ambient temperature is with the blower running full tilt and likely on a machine that's open to ambient air.

I seriously doubt anyone would put in excess iron and copper (weight) into a car so you can derate the motor and run it without a blower.

car -> golf cart


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## GeorgeH (Sep 4, 2020)

I highly encourage forced air on DC motors for the reasons mentioned above by Major. An air filter will also help eliminate any contaminants and abrasives from getting sucked into the motor


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## ElectriCar (Jun 15, 2008)

I’m nearing startup of a Kostov11 that came with a small blower. With a Soliton and programmable outputs I’m wondering whether to use that with the motor temp switch or just let it run on ignition. Running an automatic trans with an idle setting.

Did away with the Iota dc-dc so running an alternator.


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## Jb24601 (Aug 29, 2019)

After some experience, I can say my 130cfm bilge blower does keep the motor cooler as it’s running, at least 15 degrees, and helps it cool off when stopped. I’ve seen 20 degree drops in twenty minutes with the fan running after a drive. Air flow out is not as great as inflow, but you can feel the hot air flowing out.


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