Lenze Variable Speed Drive (VSD) internals

My intuition tells me that you are trying to build a 30kW electric car, and have only a 16kW Lenze 9327 motor controller.

If you purchased another 9327, would the total cost be more or or less than the 9329.

You could then run 2 16kW motors on separate wheels

Would that work for you?

Hi Lleros. Thanks for answering. You are pretty much right. I'd been looking for a long time for a 30kW but prices are always high. I had been pontificating a DIY drive but pricing the components showed that it was a bit of a joke - let alone the work involved. The 16kW are inexpensive and when I found that lenze used the same frame size for their 16,22 and 30kW I thought I'd take the gamble. I have disassembled it and sure enough the IGBTs are standard sized and the drive will easily take a 150Amp version without modification. But that leaves me either 'lying' to the the drive current measurement system or finding the nice, clean correct way to 'adjust' it - namely changing it's personality to a 9329. I don't have a lot of money invested in this yet so I'm sounding out lots of service places and forums to see if anyone has an inside on Lenze 9300s BEFORE I spend the time and money. The AC motor will be driving a rear wheel drive tail shaft directly - so I really need the single inverter.

Are you sure that 16kW will not be enough; we did a bunch of GEO Metro conversions w/ 21kW drives. They were adequate.

We also did 2 motors, mechanically coupled; each @ 320kW (remember: X2). This was to reduce under floor diameter, + the inverter capacity was limited. For a standard USA school bus.

The current measure methode inside the frequency converter will probably the biggest problem. Usually they use hall current sensors to measure AC currents directly. Is it possible to chance them or, when the current sensor is build arround a small "tranformator" you could wind off one tour of the winding.

Every thing without the usually liability...

Hi. Yes I need about 3 times the motor capacity which is 11kW. Since the motor pullout torque is around 3 times normal which draws 20 Amps, I need 60 Amps with a peak around 100 for very low RPM startup. That means a 30kW drive with 150% overlaod capability. (People who have already done this use 37kW drives on 11kW motors but that is slightly overkill. See www.evalbum.com\1149) Thanks for advice re hall effect devices or CTs. I guess I will have to ask Lenze if the driver board is the same for all 3 power levels of drive in this enclosure. The 16kW will move it OK but I will have half available torque up to about 20km/hr.

You could always purchase a 30 kW model on approval, pull it to bits as far as you need to to see tne differences, put it back together and send it back as unsuitable. Rotten thing to do, I wouldn't want to be the one to purchase the unit afterwards, but Lenze would have to honour the warranty.

(Alternatively go to one of their approved repair centres, and see if there is one pulled to bits there)

That's a bit further down the path of skullduggery that I'd want to go but I get your idea. I haven't yet asked Lenze or their agent here the direct question but I have collected a few scraps of info. For instance one of the possible error reports the drive can emit informs you that the driver board does not match the drive model. I have to run it up and test it first (just reassembled) and when I've done that I will strip the power module completely and check out the current measurement system. Meanwhile - any Lenze service people out there?

Yes. I haven't done a comparison of the internals of the 16, 22 and 30kW (although I have disassembled the larger ones) but I know a bit about the workings of the smaller models. I have also considered the use of the smaller Lenze drives for electric go-cart racers.

The Lenze drive is fairly smart (sometimes too smart for its own good) and has plenty of safety voltage and current monitoring hardware that is going to be difficult to bypass. You really need a lot of experience if you are going to play around with the control board as it as mostly covered in surface-mount devices.

Are you sure that reducing the vehicle weight or starting acceleration wouldn't be enough to allow a single smaller VSD to be used.

I have not been able to ever get any technical information or circuit diagrams out of Lenze (or AC Tech) to date for fault finding and diagnostic purposes so I believe you will be on your own there.

Oh, and what you are doing will void the VSD warranty.

Hi jack... You don't fill me full of hope. I had sort of hoped that worst case I would only need to fudge the motor output current measurement. The drive in it's current form will give me about 150NM of torque but the motor has 200 available which I can only use if the drive can deliver around 90 Amps (the 9327 is good for 48 peak). The VSD warranty expired years ago - I bought it second hand for a reasonably low price - hence the attempts to get a 'bit more' from it.

It would really be a shame to damage the drive electronics. I have checked but we are all out of the large VSD's here (so no luck there).

Do you have the motor already? If so, I would suggest just using what you have and try it with the un-modified drive you have. You can alter the VSD's Fixed Boost, Acceleration Boost, Overload, etc to give you better performance (which may be enough). You will likely find that it is a lot EASIER to alter the mechanical gearing to provide the extra torque than trying to alter the VSD.

Do you realise that you can run the VSD at a higher maximum speed (up to 240Hz) using parameter 24 "Maximum Frequency" to compensate for the higher gear ratio? This should be enough to give you high torque initially (when stopped) and good speed when moving.

What do you think?

Hi jack...

The following graph (though not for my motor) gives you an idea where the torque would be lacking. The target is to get 100km/hr at around 4000 RPM.

1500 RPM is around 41 kw/hr. My motor doesn't get to 250NM as in the graph but my motor's TN is 3.0 with rated torque as 72NM so it gives just over 210NM. You can see that below 1000 RPM the 48 Amp limit of the drive would be holding torque back.

The pic is blurry but the 9327 is the line just above 150NM. The lines up around 250NM are for 88 Amps. Practically I need somewhere around 80 Amps (for a few seconds) instead of the 48 Amp the 9327 delivers - other than that the 9327 will be fine.

The important thing is that, with direct drive, I may have trouble 'getting off the mark' on a hill.

You do realise that your "hobby" is professionally serious, and making a hobby electric car to do 100 km per hour is potentially dangerous.

If you do happen to invent or develop something novel using bodgey parts, you cant patent nor sell the idea. I suggest that there enough amateur fiddlers "inventing" by tinkering with harmless devices, withour trying to make an unprofessioanally designed electric car.

I suggest you either bite the money bullet and do the job professionally with parts designed for the job or you stop now.

As a professional QA expert, I am sick and tired of technicians redesigning (eg a system on a Linear accelerator) thereby invalidating the manufacturer's legal warranty protection and masking the standard symtom/problem set, making a completely new set of symptoms for the manufacturers' service personal to puddle through when things dont work and you are no longer around (or you sold the job).

It's a great project. Do it properly do it well and dont leave yourself open to criticism

Lleros

I consider myself slapped on the wrist. This project is for my own use and I am actually quite professional in what I do. I have no delusions of manufacturing electric cars - the 'real' manufacturers will have them soon enough. I also don't tend to flame others as you appear to have just done. A budget is a budget. Whether the controller has been modified or built from scratch the vehicle still has to pass scrutiny from the road authorities here. Thanks for your input.

I still think using a higher gear ratio and increasing the VSD speed parameter would be better than you trying to modify the VSD internals, there should be enough headroom to get close to what you want without risking damage to the VSD. It would not be to difficult and expensive to play around with the mechanical gears and an un-modified VSD first, if that doesn't give you the result then you could always take the chance and try and modify the VSD. Just remember to wear safety glasses and have a fire extinguisher handy, I have seen my far share of VSD explosions first hand.

Oh, and the Lenze VSD's don't seem to have discharge circuitry across the storage capacitors so ALWAYS discharge them first and connect a resistor across until you have finished (I have been bitten a couple of times after a "discharged" capacitor recovered enough voltage to zap me).

What are you planning on using to power the VSD? Car batteries (while they have good cranking current) have lousy Ah capacity and lousy power to weight ratio which will seriously limit the vehicle's range.

Hi jack... Point taken. I have 2 differentials lined up. The one in the car presently is 3.89:1. I also have a 4.2 and I have 'reserved' a 4.78 and 5.2 from someone who I recently contacted. With that, I think am well prepared for ratio changes. The top speed of the motor becomes an issue with the 5.2 so I'd like to avoid that. Based on what you are saying I think I will try the drive unmodified and see how it goes - I'm not after a drag machine, just a daily driver. Thanks for the warning on the Caps. I noted the warnings in the manual and on the case but it doesn't hurt to be reminded. The drive was in cosmetically poor shape when I got it with the internal plastic work holding the caps cracked and displaced by poor treatment - all good now - looks like new (and it works). I am intending to use AGM batteries initially (GreenSavers actually) - 48 of 12V 20AH with 6 x 400 VDC contactors to break the system into 96 volts chunks. They should last 2 years at which time I will be ready for Litium Iron Phosphate (financially). I notice about 38 ohms resistance from either + and - of the DC BUS to + and - the caps. It looks like this drive have a precharge system from the DC bus to the caps.

Johny451:

A couple of questions for you:

Have you considered simply replacing the gasoline engine with your electric motor and retaining the clutch and transmission? It's a mechanical workaround to get the torque you need for decent starts. The clutch isn't really necessary, but it will help the gear changing. This workaround will address your problem with low starting torque and you might be able to live with the 11kW drive without modification.

I have been considering retrofitting a vehicle but have been looking at the DC drive route, and this post caught me by surprise. I'm guessing that you are planning on cutting into the DC bus in the VFD and supplying it with nice pure DC from the batteries. I'm also guessing that the Lenze drive is 240V or thereabouts....what DC voltage do you need to provide to the drive?

Sounds like a fun project. Good luck on it, and don't let the safety cops put a damper on things! (Doesn't it seem like the safety guys always have a "can't do" attitude...why can't they have a "can do, but watch out for...." attitude?) Your posts have been thoughtful and I don't expect that you will do anything silly. I'd like to be helping!

Jon.

Hi Jon. Thanks for the positive feedback - I may have picked the wrong forum for this kind of thing. I actually started down the track on the DC path but tended to veer toward direct drive as the 'donor' car (wife hates that term) is an automatic - so no manual gearbox. For direct drive DC the motor was getting a tad large and the DC controller for it also expensive. The spark went off for AC when I saw a vehicle in evalbum that used a Danfoss 37kW VSD. Have previous experience in high power DC drives in industry it seemed the right direction to go. The peak torque from a 3 phase motor can be around 450% if the current is available (not normally used on an industry setup). An EV would only use this for a couple of seconds. I am planning on using a 415 VAC 3 phase 4 pole motor - 11kW but that's because I can get one that only weighs 60kg (ABB or CMG in a 132 frame). I agree that a gearbox would be the go but a higher powered drive would also give me the 0-20km/hr torque I need and it's probably less expensive to just go buy the drive. I have a backup Chinese drive that I have been emailing back and forth with the company but I wanted to try the IGBT upgrade path in this one first as the drive I have owes me very little. Oh, batteries will be 600VDC made up of 48 of 12 V x 20AH. When they expire I should be ready to go Lithium. It's a huge compromise between weight/torque and highest RPM. Keep the motor as light as possible and still get up the hills at a reasonable speed.

Johny451:

Nice design! I like the high voltage 'cause it will sure cut down on the cable size and IsquaredR losses! The batteries seem a little small--what are you projecting for the range between charges?

Just think of the possibilities if you made this up in a little truck: you could run a 3 phase welding machine, run a big compressor, and do all sorts of silly 3 phase stuff!

My application needs 75km to/from work at 100 km/h. It seems that 20 x 6V "golf cart" sized batteries would be barely enough to go one way. Not sure what the total energy is in that 1300 lb lump of lead is!

I have access to lots of detailed info on Mitsubishi VFD's but I don't think this would be of much help to your effort. Let me know if you want anything.

Never heard of a "132" frame--is this some sort of lightweight aluminium framed motor? It's gotta be fairly well made to give 450% for any length of time.

By the way, is the drive a "vector" drive or a "plain" VFD? It seems to me that you will get a lot better starting and low speed running torque with a vector drive as compared to a VFD.

Jon.

Hi sawmilleng Yes it's a vector drive. I spent months reviewing specs and chasing prices on drives and generally found out that, so long as they have are vector, have a DC bus option and torque control (see later), they are fine for EV work. I'll be the first with a Lenze I think (my cheapest option at the time - 2nd hand). The battery pack works out to 12Kw/hr and after Peukert effect I'm aiming for 6Kw/Hr usable at 50 depth of discharge. I need a 30km range so if I can get 200W/km I should be on target. My workplace is OK with me charging there if the range is off. After 2 years when the lead acids are aged I hope to go Lithium Iron Phosphate - have to prove the concept to spouse for financial approval on those. She's still not sure I'm not collecting a garage full of industrial electronic waste! The motor I'm hoping to use is a CMG 11kw 'high output' design. No longer bought into Australia due to efficiency regulations but it's only off by 1% and is considerably lighter than the next motor frame size up. Hoping to get one from UK - the alternative is an aluminium from 11kW from ABB. Have a look at www.evalbum.com/1149 VFDs have different features but the Lenze is nice in that you can control the maximum current as a motor and separately as a generator. So I shouldn't cook my batteries on regen. I note sidevalveguru comment on the 'go faster pedal'. Yes, torque control is a must from what I have gleaned. It seems I should also run a speed encoder so that low speed control is predictable. The Lenze is a bit annoying here as other drives (Danfoss for instance) allow just an inductive pickup for speed feedback but the Lenze insists on a full sin-cos encoder. BTW if anyone is interested in electric vehicles or maybe starting one, the AEVA site is: http://www.aeva.asn.au/forums/ There are lots of AC motor discussions there.

For sure: AC drives are the most flexible. Some early attempts forgot that the 'go-faster' pedal was a power control, rather than rpm. Results were unsatisfactory.

Regenerative drive is very worthwhile!