# High voltade doubler for ev; igtb driver



## frodus (Apr 12, 2008)

Why do you need/want to double the voltage?


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## cts_casemod (Aug 23, 2012)

frodus said:


> Why do you need/want to double the voltage?


Because my motor runs off 600VDC


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## frodus (Apr 12, 2008)

And by doubling you half the current. Why not either build a pack for 600VDC with lower AH batteries, or get a motor that runs off of your 320V pack?

The sheer cost and size of the components needed for the power levels you need will put you off...... almost positive of it.


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## cts_casemod (Aug 23, 2012)

frodus said:


> And by doubling you half the current. Why not either build a pack for 600VDC with lower AH batteries, or get a motor that runs off of your 320V pack?
> 
> The sheer cost and size of the components needed for the power levels you need will put you off...... almost positive of it.


I am asking advice from people that have worked with IGTBs and have experience driving them as I already have a working prototype done with a smaller 2HP motor, using mosfets.

Half current -> Double voltage = Same Power
Here in Europe you can not find 220V AC motors so easy as in the USA, you find 415V wich require a working voltage of >600VDC

If I start thinking in the price for an extra 320V BMS, Charger, extra batteries, etc that I need to run the doubler price is not relevant.


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## frodus (Apr 12, 2008)

I do have some experience, which is why I asked. I realize it's the same power output as low voltage/higher current. You're going to be in the 50-100kw range or higher with an EV and that won't come easy.

Look up Boost Converter on here, it's been discussed quite a bit before. IMHO You would be much better off just having a USA motor shipped there. The cost of a doubler that can handle that much power is going to be large, heavy and expsensive.

Good luck with it.


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## dougingraham (Jul 26, 2011)

cts_casemod said:


> Because my motor runs off 600VDC


Nothing wrong with 600VDC. The issue is the the doubler.

You don't want a voltage doubler. Don't think of it as the motor current being half, instead think of it as the battery current being twice as much.

You don't want a voltage doubler. To get 100kw your doubler could weigh around 50kg (110lbs). The additional weight and space consumed would be unfortunate. Better to spend that weight budget on more batteries.

You don't want a voltage doubler. The doubler if done well will have an efficiency of 92%. That means an 8% loss of range just due to the doubler. It also generates considerable additional heat. With a typical cruising power level of 15kw there would be at least 1200 watts of waste heat. This is like a ceramic space heater output. If not done well the waste would be more than twice this.

You don't want a voltage doubler. In a one off if you make everything yourself you are looking at a device that will cost on the order of $1000. A commercially produced unit with sufficient production volume would get back to $1000 but in the small quantities we are talking about this would be $3000 to perhaps $5000. This buys a lot of additional batteries.

So to sum it all up you probably dont want to do this. It might seem like a simple solution but it isn't. Instead double the number of cells and cut the capacity in half. It moves the problem to the charger and DC-DC converter but those devices don't need to handle 100kw or more so the problems are a lot easier to deal with.

Best Wishes!


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## cts_casemod (Aug 23, 2012)

The electric motor to replace the 45HP ICE on the car will be driven at 15KW/20HP with a peak of 20KW. I am not planing to go into hundreds of KW. This will be a city car, all that will be required is a motor capable of doing hills at 25MPH with a top speed of 40MPH.

Battey pack will be 7.4KW with a range of 25 miles.

Ths car will weight about 850Kg/1900lbs

My Battery pack is 320V @ 20Amp, 100S2P, it could be modified as [email protected], 200S with the propper BMS and having 20 chargers on board

I do not believe the doubler itself would be more that 10Kg in weight, the heavier items are the capacitors, 2 x 400VDC wich size will depend on the frequency. As I said I am loooking into 80Amp peak from the 320V Side.

Running at 320V would allow me a simpler BMS and charger and to run an electric aircon and standard DC-DC Converters. Both could be run straight from the mains at a charge point.

I like the idea of running a 208V USA Motor, problem is finding a suitable VFD, which would end up having to come from the USA as well (more money, more customs, etc).

In terms of efficiency you're right dougingraham I will have a 92% efficiency, however even if I used a 208V motor the losses will be there anyway as the IGTBs on the controller would had to take twice the current anyway and using 640V I would need a 2 or 3KW converter to power the power supply and AirCon, so, again more losses, even thought having a smaller current.


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## Bford (Sep 12, 2012)

I usually just lurk and read...

Couldn't you just re-wire your battery packs to get the required voltage?


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## cts_casemod (Aug 23, 2012)

Bford said:


> I usually just lurk and read...
> 
> Couldn't you just re-wire your battery packs to get the required voltage?



Maybe because I want a 320VDC Main bus voltage.

Whats so hard to understand about that?


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## onegreenev (May 18, 2012)

So just add in another 100 cells of 20 AH. It would be cheaper. I am guessing maybe your using A123 cell pouches. I have 50 of them and they really don't take much space. So if that is what your doing you will still have your 20 amps and 640 volts and a nice city cruiser. No extra heavy expensive doubler that would tax the pouch cells. 

This would be a nice 12.8kWh pack. Nice for city driving. 

So what cells are you using? 

Pete


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## topau (Jul 12, 2012)

cts_casemod said:


> I like the idea of running a 208V USA Motor, problem is finding a suitable VFD, which would end up having to come from the USA as well (more money, more customs, etc).


Tehnically speaking you can use many of the European VFDs with 320Vdc, even thought they are rated for 400Vac input (= 540Vdc DC-link voltage). You only need to disable the input phase supervision and change the DC-link low limit. Only thing you need to check is that you have the output current rated for enough current. As 400Vac drives are using 1200V rated IGBTs, you are getting 1% more losses on IGBT on resistance, compared to 600V IGBTs. This is due to 600V IGBTs having smaller ON-state resistance.

Commercially: The price is bit higher for the same current for 400Vac vs 200Vac.

Personally I will go the 540-600Vdc route having 180 cells in series.


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## jddcircuit (Mar 18, 2010)

cts_casemod said:


> The electric motor to replace the 45HP ICE on the car will be driven at 15KW/20HP with a peak of 20KW. I am not planing to go into hundreds of KW. This will be a city car, all that will be required is a motor capable of doing hills at 25MPH with a top speed of 40MPH.
> 
> Battey pack will be 7.4KW with a range of 25 miles.
> 
> ...



cts,
The gen 2 Toyota Prius 2004-2009 inverter has a battery boost converter inside it. I have one but haven't tested it out yet. I think it boosts a 200VDC pack to 500VDC. I think there may be a 500V limit built into the hardware from what I have read but not sure yet. It is rated at 20kW so that's 100 battery amps. It does not weigh that much, I would guess 10lbs at most for the boost components. These are not exactly the numbers you are looking for but maybe you could hack it and expand its operating range.

I think the benefit for this hybrid is that it is easier for the inverter to create a nice sine wave with low current ripple at low speeds switching the unboosted 200V pack but at higher motor rpms and higher back emf it then boosts the battery pack voltage proportional to the back emf and switches more to a six step commutation mode in phase with the rotor angle. I guess at these higher speeds and lower motor current the torque ripple is less of a concern.

Good luck
Jeff


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## cts_casemod (Aug 23, 2012)

topau said:


> Tehnically speaking you can use many of the European VFDs with 320Vdc, even thought they are rated for 400Vac input (= 540Vdc DC-link voltage). You only need to disable the input phase supervision and change the DC-link low limit. Only thing you need to check is that you have the output current rated for enough current. As 400Vac drives are using 1200V rated IGBTs, you are getting 1% more losses on IGBT on resistance, compared to 600V IGBTs. This is due to 600V IGBTs having smaller ON-state resistance.
> 
> Commercially: The price is bit higher for the same current for 400Vac vs 200Vac.
> 
> Personally I will go the 540-600Vdc route having 180 cells in series.


I have planed to do this already in case of a DC-DC Failure, to have a limp mode.
Technicaly yes, you can use the electronics of the VSD and change the power part. The guy on the passat has done this for his 90HP Controller.

If I were to use a 208V motor I would use mosfets rated for 800V, for 600V I have no option but to go with 1.2KV IGTBs.

On-Resistance? They have a voltage drop like a transistor, not like a mosfet  But yes, the drop will be higher with 1.2KV.

This is all about cost. Shipping from the USA is out of question
15 12 Cells BMS's for 30-60A arent cheap either, at 40 + taxes = Shipping each.

I am still not convinced. 
The converter would be about 600USD/400GBP to build. The pair of IGTB's would be the most expensive.


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## cts_casemod (Aug 23, 2012)

jddcircuit said:


> cts,
> The gen 2 Toyota Prius 2004-2009 inverter has a battery boost converter inside it. I have one but haven't tested it out yet. I think it boosts a 200VDC pack to 500VDC. I think there may be a 500V limit built into the hardware from what I have read but not sure yet. It is rated at 20kW so that's 100 battery amps. It does not weigh that much, I would guess 10lbs at most for the boost components. These are not exactly the numbers you are looking for but maybe you could hack it and expand its operating range.
> 
> I think the benefit for this hybrid is that it is easier for the inverter to create a nice sine wave with low current ripple at low speeds switching the unboosted 200V pack but at higher motor rpms and higher back emf it then boosts the battery pack voltage proportional to the back emf and switches more to a six step commutation mode in phase with the rotor angle. I guess at these higher speeds and lower motor current the torque ripple is less of a concern.
> ...


Thats a good thing to know about Jeff. 
I will look into ebay to see if I can find something like that. 
10 to 15lbs is the weight I have calculated althought everyone here says it should be more.

My whole 15KW VSD weight is 23lbs. 
People I am not using brick transformers, I am using a charge pump.


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## jddcircuit (Mar 18, 2010)

cts_casemod said:


> Thats a good thing to know about Jeff.
> I will look into ebay to see if I can find something like that.
> 10 to 15lbs is the weight I have calculated althought everyone here says it should be more.
> 
> ...


The whole inverter weighs quite a bit more. The inductor and the IGBT pair module for the boost are modular and easily removed to place on your own heat sink. You will just need to supply 12V and a PWM signal to regulate the boost. I think there is also a reference voltage for feedback to your controller.

I think I read that it is in the high 90's as far as efficiency goes.


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## cts_casemod (Aug 23, 2012)

jddcircuit said:


> The whole inverter weighs quite a bit more. The inductor and the IGBT pair module for the boost are modular and easily removed to place on your own heat sink. You will just need to supply 12V and a PWM signal to regulate the boost. I think there is also a reference voltage for feedback to your controller.
> 
> I think I read that it is in the high 90's as far as efficiency goes.


When you say the whole inverter you say the boost unit or the boost unit + the motor controller? Is this togheter on a single box?

I was looking into ebay and found an AC compressor for the prius. Its fully electric. Might be usefull for us.


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## jddcircuit (Mar 18, 2010)

cts_casemod said:


> When you say the whole inverter you say the boost unit or the boost unit + the motor controller? Is this togheter on a single box?
> 
> I was looking into ebay and found an AC compressor for the prius. Its fully electric. Might be usefull for us.


The Prius inverter contains the 20kw boost converter, 50 kw inverter for Motor2, 30kw inverter for motor 1. It also has a DC to DC converter for 12V output and another inverter for driving the air conditioning compressor.

All of these electronics are controlled by a separate controller not included. You will have to provide the control signals (ie the PWM signal for setting the boost converter duty cycle). It will take some research on your part.

You can search for Toyota ORNL report for some good information.
check out this link.

http://k0bg.com/images/pdf/890029.pdf

Jeff


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## cts_casemod (Aug 23, 2012)

jddcircuit said:


> The Prius inverter contains the 20kw boost converter, 50 kw inverter for Motor2, 30kw inverter for motor 1. It also has a DC to DC converter for 12V output and another inverter for driving the air conditioning compressor.
> 
> All of these electronics are controlled by a separate controller not included. You will have to provide the control signals (ie the PWM signal for setting the boost converter duty cycle). It will take some research on your part.
> 
> ...


50KW?? Can this thing run on electric mode only?

Seems like too much trouble. I thought it was only the booster.


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## Tesseract (Sep 27, 2008)

cts_casemod said:


> ...
> People I am not using brick transformers, I am using a charge pump.


You use charge pumps for supplying a few watts of power; for 10-20kW or more you'll want to use an interleaved boost converter.

I'm not going to tell you whether I think this is a good idea or a bad one; I'll let you determine that for yourself the hard way.

Oh, and it is IGBT, for Insulated Gate Bipolar Transistor, not IGTB.


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## cts_casemod (Aug 23, 2012)

Tesseract said:


> You use charge pumps for supplying a few watts of power; for 10-20kW or more you'll want to use an interleaved boost converter.
> 
> I'm not going to tell you whether I think this is a good idea or a bad one; I'll let you determine that for yourself the hard way.
> 
> Oh, and it is IGBT, for Insulated Gate Bipolar Transistor, not IGTB.


I used them for my prototype with Mosfets at 2 KW with decent output, hardest thing was to find 400V low ESR Capacitors. I do not have experience using IGBT's thats why I posted here.

The reason I am posting is in fact because I have this prototype and its operating a small 2 HP motor from 24VDC with success (24 to 320 - 320 to ~600). I am not asking an opinion, neither am I saying that my idea is the best. I am asking a solution for my problem.

What I need is either:

*a)* 640V battery pack, in which case I will need a booster for the charger and a 2 or 3KW converter back to 320V for AirCon/Heater/PSU operation

*b)* 320V Battery pack with a boost option to feed the motor.

Regarding interleaved boost converters I have thought about that but have no experience working with coils or where to order the proper ones. I have not find a lot of technically oriented people here to answer this questions, thats the reason I have not went thought that route.

You seem to be quite familiar with this, is there anything you may want to advise me in regards to the options i gave above?

Regards


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## PStechPaul (May 1, 2012)

I built a DC-DC converter that was able to convert 12 VDC or 24 VDC to about 320 VDC and I ran a 2HP three phase motor with a standard VFD. But that was for a small tractor, where I plan to use two or three lead batteries and maybe 5-10 HP maximum intermittent duty. 

For my design I used a toroid transformer specially wound for higher frequency, and I found that it would work OK from about 600 Hz to 6 kHz. For about 2kW the transformer might weigh about 10 lb. I ran into problems because the square wave drive into a capacitive load caused huge current surges that destroyed the MOSFETs, and there were also high voltage switching transients that had to be dealt with, using inefficient snubbers and slower gate transitions which also add to losses.

I have come to the conclusion that it is impractical to use such a DC-DC converter for a larger vehicle like a car, with power levels of 20-50 kW or more. Using higher frequency and ferrite components would probably be more practical but it would involve essentially the equivalent of 20 1000W switching supplies, and each one would probably be about 5-10 lb and cost at least $100 each.

It would be interesting to see your 2HP prototype in operation and to examine some of the design parameters and view waveforms and such. Capacitive multipliers are generally used for low power applications and I'm not sure how well they scale up to the multiple kW range. It would be helpful to do an LTSpice simulation and determine the current and voltage waveforms involved and the value and ESR required for the capacitors. Also, using a capacitive charge (or inductive energy) transfer will be very sensitive to load compared to using a transformer.


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## cts_casemod (Aug 23, 2012)

Hi again Paul,

I have only used the inverter because 

a) I could test it at my garage where there is no AC power, yet I have 12, 24 and 36V Available from batteries

b) I was too lazy to built my own DC to AC inverter using mosfets so I have used the output of the DC-AC Converter and changed the frequency from 50 to 400Hz. These mosfets tend to get hot at 400Hz due to the simple gate driver, yet the voltage at the capacitors is pretty stable unlike at 50Hz, I got 600V at full load during a couple of seconds (the mosfets got hot). At 50Hz I got 380-420V. 

I have no ideas to use a transformer, maybe a coil


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## cts_casemod (Aug 23, 2012)

PStechPaul said:


> Capacitive multipliers are generally used for low power applications and I'm not sure how well they scale up to the multiple kW range.


Check out my conversion topic 

http://www.diyelectriccar.com/forums/showthread.php?p=322481#post322481

First run, of the motor, I still need to set up the VSD properly, the motor is not runing smoothly.
The whole thing is running using a voltage doubler with parts from a damaged VSD using a similar topology found on ATX computer power supplies for use on the USA. (110AC to 320DC)

The capacitors were powerfull enought to trip the 13Amp Circuit breaker, while keeping voltages above 600VDC.


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