AC or DC motors ?

2291 Views 7 Replies 5 Participants Last post by corbin, Oct 18, 2010

salva

Discussion Starter · Oct 17, 2010 (Edited)

Hello there, I have discovered EV and this site over the last week and I am bougth by it!!, I have been reading a lot and still I have lots of doubts, on top of them is the motor type you have to use for your EV. I understand that you have the following types of motors for EV:

DC (Sepex, Shunted, Permanent Magnet)
AC

Why will you use one or the other?, most projects that I have seem use DC shunted motors and in small vehicles PM is the most prevalent type.

Why AC is not the preferred type?

I understand that AC has cero mantenaince but smaller efficiency but I wonder what are the main factors, technically and money wise, to select a particular motor technology for an EV.

Thanks for sharing your tougths.

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Qer

· #2 · Oct 17, 2010

salva said:
most projects that I have seem use DC shunted motors

Nope, you got that mixed up. Series wound is the most common motor type for DIYers.

salva said:
Why AC is not the preferred type?

Expensive.

salva said:
I understand that AC has cero mantenaince but smaller efficiency

Nope, got that one mixed up too. An AC-MOTOR has higher efficiency than a series wound DC-motor but an AC-CONTROLLER has lower. In the end the difference is generally to the AC systems advantage, but the difference is also generally speaking pretty small when you consider what you get for your money. Buying more batteries to compensate is usually more economical.

For more details I recommend the search function. This topic has been convered several times in this forum in more or less friendly tone...

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salva

Discussion Starter · #3 · Oct 17, 2010

Qer said:
In the end the difference is generally to the AC systems advantage, but the difference is also generally speaking pretty small when you consider what you get for your money. Buying more batteries to compensate is usually more economical.

Thanks for your comments and corrections, so I understand that all comes down to power to $$$ ratio in the end.

still lots to learn

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Qer

· #4 · Oct 17, 2010

salva said:
Thanks for your comments and corrections, so I understand that all comes down to power to $$$ ratio in the end.

Yep. Plus that if you want POWER (as in racing) you're pretty much limited to DC. At least I haven't seen any AC-systems for sale, no matter price, that's even close to dish out the powers the high end DC-controllers can provide.

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Crash

· #5 · Oct 17, 2010

Actually, DC motors can be quite expensive as well. Look at UQM. Their motors are DC and the prices are simply ridiculous.

However, I'd agree that the majority of DC motors widely available are far less expensive than the majority of available AC motor/controller setups.

For a first time conversion, it's usually a good recommendation to go with DC. The reason for this is that the majority of AC setups require higher voltage which in turn can also make your setup more expensive and more complicated. DC setups are a bit more simple to setup and are usually lower voltage.

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major

· #6 · Oct 17, 2010

Crash said:
Actually, DC motors can be quite expensive as well. Look at UQM. Their motors are DC and the prices are simply ridiculous.

UQM are AC motors, just using permanent magnet rotors, and called BLDC.

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major

· #7 · Oct 17, 2010

Qer said:
Yep. Plus that if you want POWER (as in racing) you're pretty much limited to DC.

Seems to be the case for drag racers. But the top circuit racers use AC drives

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corbin

· #8 · Oct 18, 2010

Hi Salva,
I did my own research on AC vs DC not too long ago. I got a lot of great information from many people on this forum. Here is what I came up with:

http://www.corbinstreehouse.com/blog/2010/04/plug-bug-ac-vs-dc/

Then an analysis of available motors:

http://www.corbinstreehouse.com/blog/2010/04/plug-bug-ev-ac-drive-motor-controller-selection/
http://www.corbinstreehouse.com/blog/2010/05/plug-bug-more-motor-comparisions/

In the end, I went DC, mainly due to price and ease of use.
http://www.corbinstreehouse.com/blog/2010/05/plug-bug-final-motor-selection/

corbin

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