Fan Motor is very hot after shutdown

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Old 04-11-14, 04:37 AM
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Fan Motor is very hot after shutdown

Hi

Yesterday I plugged an office fan to an inverter with built-in UPS and battery charger, this inverter is plugged to 2 batteries,the fan works but the motor sound is a little higher and after turning it off, the temperature of the motor raise up gradually until it's very very hot, Although it's not hot while working, just after turning off.

I tested more than a once.

The inverter is NOT pure sine wave.

When I plug the fan to the normal electric (government electric) it doesn't be hot after turning off.

If I will turn it on via the inverter when power outages, is there any danger ?
 
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Old 04-11-14, 05:27 AM
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It sounds like the motor is working harder then it should. What is the watts or amps of the fan, compared to the watt output of the inverter?
 
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Old 04-11-14, 08:18 AM
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Fan wat : 70
Fan Volt : 220 : 240

Inverter max watt : 600 watt
Inverter Amps Input : 5.6
Inverter Amps output : 3.3

When the inverter working with the electric of the batteries output Volt is fixed at 230, while when its working at the normal electric output Volt is moving between 220 : 230


This problem happens only when the inverter works with the electric of the batteries.

But if the inverter working with the normal electric (government electric) the fan working normally without any problem.
 
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Old 04-11-14, 10:50 AM
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Because unless it is an expensive "True Sine" inverter, the AC wave produced by the inverter is square, and most AC motors do not like square waves. They have to work harder than they are designed to, thus get hotter. The reason it seems to heat up *after* you turn it off is because the motor is in the air stream, and is cooled down by the air flowing over it. Once you turn it off, the built-up heat continues to move outward but there is no moving air to dissipate it anymore.

My suggestion is to get a fan that will run directly off DC. Not only will it run cooler, it will run longer without the inverter wasting power.
 
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Old 04-11-14, 10:57 AM
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You mean I get a fan work with 12 Volt so I can connect it to the battery directly ?

But I have to use the inverter at any way as I use it for the Computer and Internet router as well.

Do you think it will be danger if let the fan work like this ? would the motor get damaged ?

Or there are no rule about that and I have to try and see what will happen : )) ?
 
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Old 04-11-14, 11:06 AM
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Yes, I mean get or build a fan that uses a motor designed to run directly on 12VDC (or whatever voltage the batteries are).

Electronics for the most part don't care about the shape of the wave, because the power is converted back to DC inside anyway.

Motors - since they use AC directly without conversion - are designed to ride the smooth sine wave efficiently, and when you feed them a square wave things don't go smoothly.. They have to work harder to overcome the 'stairsteps' present in a square wave..




This causes the excess heat (and FYI heat is nothing more than wasted electricity - the more heat the more waste), which accelerates wear and tear and breakdown of the motor.

And yes, I believe it would become a fire hazard because the motor is not designed to operate that hot. At the very least, if it doesn't start a fire, it WILL eventually kill the motor.
 
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Old 04-11-14, 12:43 PM
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Did you read my replies in your previous thread?
Would suggest the 12 volt fans as I previously wrote. Converters are not 100% efficient so some waste with a converter. Also consider 12 volt fluorescent or LED lights.


Read more: http://www.doityourself.com/forum/el...#ixzz2ybnEWJ00
 
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Old 04-12-14, 11:53 AM
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Thanks a lot Jersey Matt.


Did you read my replies in your previous thread?

Read more: http://www.doityourself.com/forum/el...#ixzz2yhQHlyZw
Yes I read it, but I was going to buy the inverter at any way for the P.C, that's why I preferred to connect everything throw it.

The problem for me, 12 Volt fan which I can find it here is very small one as we use it for cars as you said. The temperature here in summer up to 40 Celsius.

If I found a proper one, can I connect the fan to the batteries while the inverter is connected to the batteries ? (I have two batteries every one is 12 volt, and the input for the inverter is 24 Volt)
 
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Old 04-12-14, 01:29 PM
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Better to find a 24 volt fan or even use two identical fans in series but it probably won't hurt to wire across just one battery. One of the ones I listed was 16" IIRC. Why not order one on line.
 
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