Does a device with DC have a longer life than AC?

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Shervan360
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Hello,

Suppose we have two split Air conditioners or freeze/refrigerator compressors. First works with AC and second works with DC.
Which one has a longer life?
What are the pros and cons of compressor work with AC vs DC?

Thank you
 
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It will also depend on voltage.

For high voltages, AC has two advantages.
1. The mechanical switches will last longer, because the arc that forms when the contacts open, will be extinguished within 10 ms, at the end of the half-cycle.
2. The insulation will last longer, and have less leakage current, since electrochemical tracks will take longer to form, so there is less chance of water treeing through the insulation.

https://en.wikipedia.org/wiki/War_of_the_currents
 
Shervan360 said:
Suppose we have two split Air conditioners or freeze/refrigerator compressors. First works with AC and second works with DC.
Motors, then? I think anything brushless will win.
Within cheap devices that's a subclass for AC.
... though it's a relative new thing to have a brushless motor running on DC with some electronics, and those also can last really long, but usually for a higher price.
 
Since this thread is about Air Conditioners, I thought about updating the thread title to clarify it:

Does an AC device with DC have a longer life than AC? [/size][/size]

Er, never mind... :smile:
 
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I thought about referring to High Voltage AC as HVAC.

You cannot be a truly good person, unless you have bad thoughts, and resist them.
 
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Baluncore said:
You cannot be a truly good person, unless you have bad thoughts, and resist them.

but resisting them takes the fun out of life :wink: :wink:
 
davenn said:
but resisting them takes the fun out of life
Resistance is futile.
You must learn to appreciate more your failings as a human.

The Protestant first seeks permission, which will be refused.
The Catholic later seeks forgiveness, which will be accepted.
 
Well, lets see; with mechanical stuff it is the rubbing of the pieces that are frequently the first to fail (for instance, think motor bearings in a fan).

For incandescent light bulbs (lamps) the failure mode is most strongly related to number of On-Off cycles, then total On time. The thermal shock at turn-on is when they usually fail.
For lamps that are On continuously, those operating on DC sometimes have a problem with dimensional consistency (diameter) of the filament and with impurity levels. Both can lead to electro-migration of metal atoms away from the defect, thus causing a hot-spot that eventually burns thru.

The response above by @Baluncore (https://www.physicsforums.com/posts/7123169) also mentions some good points.

But as always, the design trade-offs have a huge effect. Think cars; some brands can be reliable for some decades, others are in the junk heap after one decade.

Conclusion: The best I can say is "It Depends."

Cheers,
Tom