# 650 V AC controller?



## Da_Fish (Apr 28, 2008)

You could build a DC-DC converter for the front side using some huge solid state devices. Problem is it would be so inefficient you would not have any range at all. The entire point of going to AC is to getter better efficiency and range.


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## Wirecutter (Jul 26, 2007)

If you want to start with an existing industrial AC drive, you should probably look for one that runs on the lowest possible voltage at the HP rating you want. And as Da_Fish advises, if you want efficiency, you _don't_ want a DC-DC converter. The other thread has some discussion about this.

http://www.diyelectriccar.com/forum...t-ac-alternating-current-systems-10402p2.html

-Mark


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## CPLTECH (Sep 14, 2007)

I am confused as to why 650V? 
What motors are available at that voltage?
A 650V system is very, very lethal (not to say lower voltage aren’t).
The highest voltages I have seen for EV’s is around 312V


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## Dennis (Feb 25, 2008)

> I am confused as to why 650V?
> What motors are available at that voltage?
> A 650V system is very, very lethal (not to say lower voltage aren’t).
> The highest voltages I have seen for EV’s is around 312V


How about across the line start 3-phase motors that run at 2,300 volts RMS or better yet, how about 4,160 volts RMS. Now that is a barbecue for sure!!


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## CPLTECH (Sep 14, 2007)

Dennis,
In the reply, I was wondering what motor he got hold of. Worked around 480 (over 650V RMS) for years and know that some take a 240/480 3ph industrial motor for use in their EV and use the lower voltage. I think other parts of the world use higher voltages, like 500-600v. 
But we need to think of the guys who come to extract us in a crash scenario.


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## Wirecutter (Jul 26, 2007)

In order to "roll your own" controller to run a 480v 3-phase motor, you need a DC bus of around 650V. Remember, it's 480V *RMS*, 650 is needed to hit the peaks.

-Mark


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## Wirecutter (Jul 26, 2007)

CPLTECH said:


> But we need to think of the guys who come to extract us in a crash scenario.


 ...or else when they arrive on scene, they won't be thinking about *you,* they'll be thinking about how to avoid getting _fried_. 

-Mark


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## CPLTECH (Sep 14, 2007)

Thanks for the correction. I should have known better. Haven’t been on a o’scope for over a yr now.
RMS voltage basically refers to the work (DC equivalent) of an AC voltage.
Peak-to-peak is how high the AC sine wave gets (the 650V P-P)

As for a controller, I often wondered if someone could take an industrial VFD controller with an input of 240VAC & modify? In a seminar a long time ago, they showed a block diagram where AC is rectified to DC & then the unit makes its own 3ph, etc. for speed regulation, braking, etc. Now the question is… How high does the voltage have to be? (In the old tube TV’s of mid-50’s, they used a voltage doubler circuit to get ~300VDC from 120VAC, so the rectified AC does become higher than the RMS. But I would think that the current draw on a VFD could not have big enough capacitors to increase the voltage by that much in a P-P scenario) So why is a 312V batt pack is used? Is it to compensate for when the pack goes lower during trip usage? That’s what I figure. These are thoughts for those planning on going that route.


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## GeEkBoY (Mar 14, 2008)

Reason I am interested in a 650V is the highlander/rx400h rear motor/differential. I have seen one for a very reasonable price but in order to get the 50kw out of it it runs at that high voltage. I am thinking a hack of the stock controller might be the best option but I am a mechie and was hoping for something simpler. I figure one of these would move a compact quite well and 2 would move a CUV effectively. I've been researching for now as my driving patterns do not suit current BEVs but with the advances in batteries, they should become feasable soon.

thanks for the suggestions, I have been following the build your own thread- probably above my skills though.


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## xrotaryguy (Jul 26, 2007)

You will NOT find a simple way to make a 3-phase speed controller. Three phase controllers are at best 3 times more complicated than simple Dc speed controllers, and they are often much more complex to take advantage of the inherent characteristics of a 3-phase controller (for regen, charging, etc).

Also, if you want to change transform pack voltage up from a lower voltage, you will first need to convert your DC current into an oscillating AC current. This is to take advantage of the inductive properties of a changing current and utilize a transformer. After you step up the voltage, you will need to convert the current back to DC. Only then can you run this high voltage through an AC speed controller. Whew! Talk about inefficient! 

I would suggest building a high voltage pack and building a 3 phase controller. That's my plan. It's an ambitious plan though. Again, a 3-phase controller is not an easy thing to build, so be careful not to bite off more than you can chew. I hope I haven't bitten off too much myself. ONOZ!


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## Madmac (Mar 14, 2008)

It is unlikely you will find a product off the shelf to do what you want. The closest might be power system for fuel cells as these have a wide voltage change to load characteristic.

For boosting by a set ratio you should be able to get an efficiency between 90 and 95%.

You may already have seen this project that is using a 600V motor for extra power
http://www.evdrive.com/BMW_project/ACmotor.html


Madmac


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