OT. EV project. Choosing an AC Drive.

I have done a variety of DC input VFD's. ALL of them had dynamic braking on them. A couple actualy had battery pack to provide the power in the event the AC input failed to allow controlled shut downs.

I do know a Yaskawa G5 or F7 drive will do what you want. I have worked on centrufuges that have one drive in constant regen, and the other going into regen when the load in the bowl gets off balance. Your 240 volts battery will power a 208 volt motor but use amps faster. To effectively have a 230 volt motor your DC should be about 300 volts nominal. Typcial 230 DC bus is 325 volts. You can limit the amount of regen energy AKA current you allow back to the DC bus. If you do a couple of long runs, liks some cart tracks have you probably will discharge enough to allow the regen of twisty turns to not exceed the bus levels. The drive has a trip setting for the max DC that you can set to prevent excessive regen. You probably will use that function a time or two getting set up. Remember, it just is not the battery charging voltage, but the voltage rating of the drive components that must be considered as well.

elevmike said:

Ok so what happens if the buss voltage dos Not exceed the battery voltage? For instance on a heavy decell with near fully charged batteries? I dont want to take out the school kid at the 1st crosswalk in the morning, but I also dont want to lose all that precious juice to heat... My thought here is a super capacitor pack to absorb the regen, then assist in acceleration, thus discharging the capacitor pack for the next decell cycle.

It seems like I might need some type of voltage converter to boost the re-gen voltage above the capacitor and/or battery voltage.

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Whoa!, listen to DickDV, with a 2 quadrant drive you will not put any power back to your batteries. The energy will be absorbed in the DC Bus of your drive. Without a true 4 quadrant drive this power will be wasted. A regular AC drive has a passive front end, just diodes.....

allscott, I didn't mean what you just said about regen. My comments about two and four quadrant apply only when using AC input.

If you hook batteries directly to the DC bus, you will get four quadrant operation even from the much-cheaper two quadrant drive.

Sorry for any confusion on that.

elevmike, you may find that the battery set will permit too much voltage rise when recharging from braking energy causing the drive to fault on high DC bus voltage. This might even occur before the recharge current reaches the maximum permitted for the batteries. I was just thinking that maybe the way to deal with that would be to electrically switch out a battery or two from the string when braking hard thus allowing maximum current to flow back to the remaining batteries. Of course, the problem with that would be a lack of balance between all the batteries.

The other potential problem you will have to address relates to charge-discharge cycles. Most batteries measure their useful life in charge-discharge cycles which would result in very short battery life in your case unless the batteries were specifically designed for that kind of service.

But then, you knew that there would be some challenges!

We got my wife a Highlander Hybrid earlier this year and I've found their battery control system absolutely amazing. One of the things it does is never allow the batteries to discharge below 20% and never allow them to charge over 80%. From what I'm told by the Toyota guys (engineers and upper level techs) this is one of the main ways they're able to get 100,000+ miles out of a set of NiMH batteries. The battery pack is 288v DC nominal and runs through a DC-DC converter to generate 650v DC for the AC drive system.

I haven't taken enough of the plastic off to see if any of their components are something commonly available from someone like Advanced Motion Control or not; maybe I'll do that this weekend... I'm sure my wife will be thrilled to see me taking apart her new toy

Originally posted by elevmike:

It seems like I might need some type of voltage converter to boost the re-gen voltage above the capacitor and/or battery voltage.

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You don't need to worry about this. Drive commutation will take care of that for you. That's a simplistic way for me to say that but I don't know how else to present it. If the drive didn't handle this you would never be able to get an AC drive to go overvoltage at anything less that full motor speed. Trus me. you can.

Origianlly posted by DickDV:

elevmike, you may find that the battery set will permit too much voltage rise when recharging from braking energy causing the drive to fault on high DC bus voltage. This might even occur before the recharge current reaches the maximum permitted for the batteries.

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That is a valid concern. I wish I knew more about batteries. I don't know the voltage/current relationship when charging. If possible I think you may want a 400 volt class drive with the ability to disable undervoltage detection. That would get you the best of both worlds.

Originally posted by marksji:

I'm sure my wife will be thrilled to see me taking apart her new toy

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Now that's taking one for the team!! I'm greatly impressed.

Keith

marksji said:

I haven't taken enough of the plastic off to see if any of their components are something commonly available from someone like Advanced Motion Control or not; maybe I'll do that this weekend... I'm sure my wife will be thrilled to see me taking apart her new toy

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Another thing you better do to your wife's car if you're going to mess with the innards is to mount a bike rack on it...:nodi:

Marksji,

I see you have posted on the "OT friday humour" thread

marksji said:

I haven't taken enough of the plastic off to see if any of their components are something commonly available from someone like Advanced Motion Control or not; maybe I'll do that this weekend...

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So you have already looked? But not close enough?

I can't decide which phrase suits my vision of you best

geniusintraining said:

• You find yourself at the airport on your vacation studying the baggag handling equipment
• You go on the rides at Disneyland and sit backwards in the chairs to see how they do the special effects

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Sadly I think I'm afflicted worse than you!

milldrone said:

So you have already looked? But not close enough?

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That'd be a big 10-4 She got a small piece of foam from a car wash logged between the headlight and the fender the other day and the only way I could get it out was to remove the headlight assembly which gave me good reason to poke around for a little while until I had to start up the grill and cook dinner

milldrone said:

I can't decide which phrase suits my vision of you best

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Easy...

I find myself at the airport/car wash/grocery store/cave tour/etc studying whatever system it is and finding ways to improve it

-EDIT-

I should probably also mention that my wife is as big a geek as I am... her geekiness is biological (catches and skins small animals, idnetifies birds while out walking, etc) and mine is electrical (like everyone else here), but at the base level we understand each other...

marksji said:

I should probably also mention that my wife is as big a geek as I am... her geekiness is biological (catches and skins small animals, idnetifies birds while out walking, etc) and mine is electrical (like everyone else here), but at the base level we understand each other...

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Oh my God! My girlfriend's a microbiologist. We're the exact same way.

Mike,

I have been thinking about your project and I'm concerned that using the acelerator pedal for regen might be a little tedious for the operator. If I'm thinking correctly the driver would have to adjust the pedal backwards only a few degrees for a coasting effect (hard to do in a moving vehicle).

elevmike said:

I also dont want to lose all that precious juice

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I'm thinking if you use the acelerator pedal for regen then you will be constantly acceling and deceling (loosing energy due to losses)

Perhaps a dual master brake cylinder could be used in conjunction with one of those aftermarket electric brake towing package controllers (the ones that use hydralic pressure to increase the electric braking action). One of the output lines from the dual master cylinder would go to the electric brake controler. the other line to your conventional hydraulic brakes. The challenge would be to get the electric brake controler to activate first then the hydraulic brakes. I know you are a fan of the DL06. I'm thinking you could use an analog input from the electric brake controler to controll the decell via a speed reference to the VFD. If you used modbus comms to the VFD, you would have access to a plethera of VFD parameters. like actual speed, current, ect.

My final thoughts are to lean on Marksji for some driver controls interface info from a user view point.

marksji said:

We got my wife a Highlander Hybrid earlier this year

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Just like this little gem.

marksji said:

I've found their battery control system absolutely amazing. One of the things it does is never allow the batteries to discharge below 20% and never allow them to charge over 80%. From what I'm told by the Toyota guys (engineers and upper level techs) this is one of the main ways they're able to get 100,000+ miles out of a set of NiMH batteries.

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elevmike said:

Re-gen & braking:
Lifting your foot from the trottle control would in effect cause breaking via the drive. In short my challage here is to cause overhauling conditions to provide some re-charging of the batteries. Any ideas on this would be appreciated.

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Your throttle pedal would become the speed reference to the drive. Simple as that. When you let off the pedal, a light spring raises it, reducing the speed input to the drive, the drive will ramp toward the new speed reference dissipating any excess energy onto the DC bus and into your capacitor bank/battery charge limiter. Set the decel rate for a nice soft deceleration.

You should be able to set up the existing hydraulic brakes to increase the free pedal travel, or dead band, so that the hydraulic brakes are not applied as readily as they are in stock form. Then use the brake light switch to trigger regen braking which could be wired as a 2nd decel rate input to the drive, or a ramp to stop with current limit. This would causing it to ramp to a stop at a faster rate. If you push harder, the mechanical brakes will join in the process of stopping the vehicle.

The brake light switch is usually set up so that the slightest application of the brake pedal will trigger it, which is what you want to trigger regen braking...

OkiePC said:

Your throttle pedal would become the speed reference to the drive. Simple as that. When you let off the pedal, a light spring raises it, reducing the speed input to the drive, the drive will ramp toward the new speed reference dissipating any excess energy onto the DC bus and into your capacitor bank/battery charge limiter. Set the decel rate for a nice soft deceleration.

You should be able to set up the existing hydraulic brakes to increase the free pedal travel, or dead band, so that the hydraulic brakes are not applied as readily as they are in stock form. Then use the brake light switch to trigger regen braking which could be wired as a 2nd decel rate input to the drive, or a ramp to stop with current limit. This would causing it to ramp to a stop at a faster rate. If you push harder, the mechanical brakes will join in the process of stopping the vehicle.

The brake light switch is usually set up so that the slightest application of the brake pedal will trigger it, which is what you want to trigger regen braking...

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Near as I can tell this is roughly how Toyota handleds it. When you lift your foot off the accelerator the electric motors begin charging the battery, but the decel is almost un-noticeable, only slightly more decel than a typical automatic with IC engine. The biggest difference is Toyota must have a variable decel rate based on brake pedal position/force because you can actually alter the battery charging rate (and decel rate of the car) by varing force on the break pedal with out ever putting much force on the friction breaks. I think that to keep things simple a drive with two discrete decel rates would be more than sufficient for regen braking.

Mike, if you get a chance stop in at a Toyota dealership and ask them to test drive a hybrid with a NAV system. Any hybrid will do, but you've got to have the touch screen that comes with the NAV system to get a good feel for how the control system works. Most likely you can even tell the Toyota guys that your simply a geek that wants to see how well it works; so far in my experience the Toyota guys will let anyone drive a hybrid that's interested in trying it out, its a cool new toy to them just like it is to us

See the pics from my wife's Highlander; you can get a sense of how their setup works from these, but to really "get it" you need to drive one and watch the energy meter along with the "NAV" screen.

I have been monitoring this post with interest, mostly just out of curiousity. However, one point has got me confused. This is probably a dumb question, but please humor me:

Isn't horsepower "horsepower"? In other words, a conventional automobile has a gas engine that delivers anywhere from 100 to 300 horsepower, depending of course on the size and type of automobile.

How do you put a 5HP electric motor on this thing and drive it with any kind of comparable power to a conventional engine? Isn't power equal to simply "work" times "distance"?

(I'm sure my next reply will be: "Duhhh, I should have thought of that.")

I notice there appears to be a tape deck in the Highlander?? But not in my Dodge ;( ...

Thoes are great shots Mark. The display seems to be designed to peak intrest so-as to challange the driver to to better driving habbits..

I have to digest some of this a little later, Lots to do.

Thanks Mike

Jimmie_Ohio said:

Isn't horsepower "horsepower"? In other words, a conventional automobile has a gas engine that delivers anywhere from 100 to 300 horsepower, depending of course on the size and type of automobile.

How do you put a 5HP electric motor on this thing and drive it with any kind of comparable power to a conventional engine? Isn't power equal to simply "work" times "distance"?

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IC motors are rated at peak HP. Electric motors are traditionally rated at continuous duty HP. If you draw 250HP out of an IC motor rated at 250HP for more than a very few minutes the motor will seize/overheat/blowup/etc.

The Highlander's rear electric motor is called a 67HP motor, but I've looked at it and from physical size alone I doubt its more than a 3 or 5 continuous duty motor.