[Johny451]

Hi all.
This is my first post here. I'm a Software Engineer witha strange desire to build an Electric Car using a 3 phase motor and an industrial Variable Speed Drive.

I need about a 30kW drive but have a limited budget. I have bought a 16kW drive with an idea to upgrading it's power.
The story unfolds...

Does anyone here have experience with the internals of Lenze 9300 serial industrial Variable Speed Controllers?
Specifically, the Lenze 9327, 9328 and 9329 (16, 22 and 30kW) all come in the same case size and weight. I have pulled my 9327 apart and it looks as if standard larger IGBTs will fit but I need to find out what stumbling blocks await me. I know that TECO VFDs let you change the Model in a parameter but Lenze play it a bit closer to their chest.
Any info anyone?

[dan_barber]

This page has some information on .pdf files. You may find the answer there.

http://www.ctiautomation.net/Lenze-F...-Inverters.htm

[kidharris]

I've thought about the same thing, however all the VFD/VSDs inverters that I have seen go from 3 phase or single phase to DC then to 3 phase @ xxxHz. How are you planning to get rid of that 1st step and go from, say, 120v DC to 230v 3 phase? Are you going to try to control the motor speed using the VSD by changing the frequency or just trying to get from DC to 3 phase? How are you going to handle regen to save the batteries? I know that driving a 3 phase motor turns it into a generator (think rotary phase converter), but how are you going to get the output back from 3 phase to DC to charge the batteries? I don't know much about electrical/electronics but I sure would be interested in any updates or more info that you would like to share.

[Johny451]

Hi kidharris
Using an industrial 3 phase VFD is surprisingly easy - sort of.
Most VFDs give access to the "DC Bus". They do this to allow all the DC Bus connections in a factory to be interconnected so that any motor acting as a generator puts power back into the bus so that others, acting as motors, can use it. They offer overvoltage protection and usually a system involving a "braking resistor" for when the DC Bus can't use the power.l

For an EV you just tack the batteries across the DC Bus. Even the internal cooling fans operate off the DC Bus (switched down to 24 VDC) so it's all pretty much taken care of.

The generator function of a 3 phase motor is just a given. If the frequency it's being fed from the VFD is lower than the motor speed should be (for that freq.) then the motor acts as a generator. Pretty much the same efficiency either way as well.

My question to the forum was not so much about how to do it, rather how to "hack" the Lenze for more current - because I'm cheap!

[kidharris]

So, how is the quest doing?

[Johny451]

Hi
Progress is slow but not so much from problem, just time. Because I won't have a speedo cable any more (direct drive to tail shaft) I have spent a fait bit of time designing a new dash. The original speedo, ODO, trip meter, fuel, temperature is all in one unit (car is 1965). I am building a direct replacement out of a spare cluster with a digital speedo in the centre (very large LCD display), and 2 of 16 by 2 line LCD displays for ODO, trip, current and kw/hr.

It's a woodgrain dash so I also have to refinish it as it's badly weather cracked. Luckily I have complete spare dash - wood and all.

It's filling in the time while I wait for a good time to stick the rear wheels (literally) back on the car so I can drive it down for a respray quote. Wife insists on respray and interior refit BEFORE the electric bit. She says it must look the part. I'm still aiming for around April 2009.

I have made contact with the engineer who has to sign it off so the motor regulator here can OK it for the road.

I haven't bought a motor yet as I'm still procrastinating whether to get a rewind to a lower voltage so I get more high-speed torque. It'll be cheaper if I do it before installing it as the rewinder and motor supplier have a 'deal'.

Whether the drive is powerful enough is sort of settled - it IS if I do not have to rewind the motor. If I run out of torque at 90k/h and therefore rewind the motor then the drive only has about half the current that I need.
I'm still trying to work this out theoretically...
How do you calculate climb gradient given rear wheel torque, radius of wheel and car mass? (Not to mention acceleration)

Oh. And I've purchased a 600 VDC 75 Amp contactor off eBay as the main contactor. I'll have more to break up the battery pack but they don't have to be able to break the DC under load. I'm up to $750 with odds and ends (the controller was $310 of that).

Still deciding about batteries but I fear it will have to be lead-acid because the AU$ went from 95 cents to the US$ in August to 64c now. It rules out Lithium as the Chinese deal in US$.
I have a list 20 to 26ah AGM batteries that I will choose from when I'm ready for them - last thing.
I have started a blog and will begin to fill it in when the car starts to look different. I'll post the address here when I start.

That's about it I think. I'll try to get the rear brakes back on this weekend - but I said that last weekend and I painted the kitchen ceiling instead (not my choice).

[Johny451]

Just in case anyone is following this thread now, here is the blog where you can track progress (slow as it is).
http://electricvogue.blogspot.com/