# Any recommendation for BLAC motor controller?



## wind81 (Sep 17, 2011)

Hi,

I think of changing the battery pack for my EV. The exisiting AC motor is actually a forklift motor 24kW 51V and running a 80V battery pack. My newly build battery pack is about 384 V using LiFePO4 battery. Can anyone here recommend a suitable and reliable BLAC motor controller for me? Thanks.


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## frodus (Apr 12, 2008)

Is it an Induction motor? Permanent Magnet AC?


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## wind81 (Sep 17, 2011)

frodus said:


> Is it an Induction motor? Permanent Magnet AC?


Look like AC induction motor.


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## frodus (Apr 12, 2008)

Any more info?
Motor make/model? other nameplate data? 
What controlled it before? Make/model on the original controller?

The less you give us, the less likely we are to be able to help.


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## wind81 (Sep 17, 2011)

frodus said:


> Any more info?
> Motor make/model? other nameplate data?
> What controlled it before? Make/model on the original controller?
> 
> The less you give us, the less likely we are to be able to help.


Hi, thanks for your reply. The motor is made from china. The name plate and performance curve is in the attachment. The name plate power rating is wrong it is 24 kW, 1440 rpm 51 V. Previously the motor is using Sevcon GEn4 controller (G8035), which only can handle up to 80VDC but currently my battery pack is 384 V.Should i used back the sevcon controller? It is easy to program it? thanks.


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## frodus (Apr 12, 2008)

I wouldn't use a 384V pack with that motor, period. You don't know what the insulation is, and it does say its only rated for 51V. I'd reconfigure your pack to work at 80V, or potentially replace the GEN4 with one of the 150V models and reconfigure your pack for lower voltage.

The sevcon isn't easy to program, but you already have the Sevcon working with that motor, so the tuning is done. It may be possible to port the values to a higher voltage Sevcon controller, but going to a different controller altogether will be problematic. Many AC motors are tuned to a specific controller. If you want a different controller for higher voltage, it will require lots of time tuning, if you can even get it working properly.


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## wind81 (Sep 17, 2011)

frodus said:


> I wouldn't use a 384V pack with that motor, period. You don't know what the insulation is, and it does say its only rated for 51V. I'd reconfigure your pack to work at 80V, or potentially replace the GEN4 with one of the 150V models and reconfigure your pack for lower voltage.
> 
> The sevcon isn't easy to program, but you already have the Sevcon working with that motor, so the tuning is done. It may be possible to port the values to a higher voltage Sevcon controller, but going to a different controller altogether will be problematic. Many AC motors are tuned to a specific controller. If you want a different controller for higher voltage, it will require lots of time tuning, if you can even get it working properly.


Hi, frodus thanks for your reply. I'm actually work on the battery pack project, which the battery pack voltage is fixed. I can't change the battery configuration. From sevcon website there is a new controller gen 4 size 8 which can cater for higher voltage of DC input up to 400 VDC. Can i used this for the motor? May i know how the motor controller input the voltage and current required to the motor? Is it possible to do the setting on the output side? Cause i don have any experince on the motor controller. Other than that, seem like i need to buy a DC-DC converter to step down the voltage? What is your opinion?


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## frodus (Apr 12, 2008)

Why can't you change the configuration of the battery pack? I find that hard to believe. 

Your motor is a low voltage motor. The windings may not be insulated well enough to use with a 384V pack. You're going to have to talk to the manufacturer of the motor about other options. Also, you'll have to talk to Sevcon to see if that controller is even available. I doubt its under $6,000USD.


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## wind81 (Sep 17, 2011)

frodus said:


> Why can't you change the configuration of the battery pack? I find that hard to believe.
> 
> Your motor is a low voltage motor. The windings may not be insulated well enough to use with a 384V pack. You're going to have to talk to the manufacturer of the motor about other options. Also, you'll have to talk to Sevcon to see if that controller is even available. I doubt its under $6,000USD.


Hi, Frodus. Actually is it constraint by the research scope. That why they make the voltage higher and want to evaluate how the battery pack performance. i have talk to the manufacturer, they said that only have low voltage motor. The other option is change the motor and also controller but that will involved another issue on mounting and vibration. I will try talk to sevcon see how much they going to sell their gen4 size 8 controller.


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## CKidder (Dec 12, 2009)

I'd like to chime in and also tell you not to do it. You've already been warned and I'll second that. Just don't do it. Below I'm going to explain why you shouldn't do it in a long, drawn out post. Feel free to ignore it and just don't do it. But, if you insist that you should do it then read the below and then don't do it.

Technically it is possible both for AC and DC motors to control the voltage to the motor by PWM such that you hit a target voltage. Of course, this is still done by opening up a connection from battery to motor so the motor will see spikes of battery voltage. The inductance of the motor acts to smooth the voltage and current back to a smoother waveform. The end result is that a high voltage source can turn into a lower voltage. A motor controller really is a special form of DC/DC converter. Even AC motor controls deep down are DC/DC converters - they just have 6 of them packed in the same case. The inductor for the DC/DC converters is your motor. In the case of a motor controller the inductor just happens to also spin.

So, what does that mean for you? It's possible that you can buy a motor controller that will allow you to take nearly 400V and control a motor rated at only around 1/8 of that voltage. But, it seems risky to me. Most motor controller algorithms are not paying a whole lot of attention to the voltage at the motor. Technically V/Hz control does but once you get to the more efficient FOC or SVM techniques they're really looking at the current waveforms and try to provide the proper output wave based on that. Now, as you probably know, where there is current there must be voltage to drive that current through the impedance presented. So, lowing the allowable current also limits voltage. But, it isn't a really intuitive or safe thing to count on. Current also varies with load so you need to allow more current when the load is higher and less current when there is no load. All while paying attention to the motoring voltage so that you don't turn the motor into a shorted fireball. A very special motor controller designed specifically for this task could do it. Plenty of DC controllers can control motor voltage specifically. AC controllers don't tend to do that and you shouldn't expect them to. 

Always use a motor that can handle your full pack voltage.


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## frodus (Apr 12, 2008)

Get a new motor/controller package that works with your high voltage.


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## wind81 (Sep 17, 2011)

CKidder said:


> I'd like to chime in and also tell you not to do it. You've already been warned and I'll second that. Just don't do it. Below I'm going to explain why you shouldn't do it in a long, drawn out post. Feel free to ignore it and just don't do it. But, if you insist that you should do it then read the below and then don't do it.
> 
> Technically it is possible both for AC and DC motors to control the voltage to the motor by PWM such that you hit a target voltage. Of course, this is still done by opening up a connection from battery to motor so the motor will see spikes of battery voltage. The inductance of the motor acts to smooth the voltage and current back to a smoother waveform. The end result is that a high voltage source can turn into a lower voltage. A motor controller really is a special form of DC/DC converter. Even AC motor controls deep down are DC/DC converters - they just have 6 of them packed in the same case. The inductor for the DC/DC converters is your motor. In the case of a motor controller the inductor just happens to also spin.
> 
> ...


Hi, CKidder. Thanks for your advise. Now i got your point and try to persuade my supervisor change the motor. But they are are worried about the vibration and drivetrain problem, will it be very serious for converted EV as compare to ICE?


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## wind81 (Sep 17, 2011)

frodus said:


> Get a new motor/controller package that works with your high voltage.


Hi, Frodus, Thanks for your comments. Do you have any experience dealing with changing the motor/controller? Will it very troublesome especially vibration and drivetrain when new motor is replace?


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## dedlast (Aug 17, 2013)

wind81 said:


> But they are are worried about the vibration and drivetrain problem, will it be very serious for converted EV as compare to ICE?


This is a case where I don't have any personal experience, but everything I've read on here says the vibration will be/should be practically nonexistent. 

Think about it, in an ICE car, for every revolution of the crank, you have a certain number of controlled explosions happening all the time. And then you have to stop and reverse the direction of travel of the mass of all of the pistons every revolution. All of that adds up to lots of bumps and bangs.

In an EV, there are no explosions (you better hope, anyway). There is no mass changing direction at any time: all the motion is rotary to start with. If the vehicle does have any vibration, there is probably something wrong and it should be fixed.

B


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## frodus (Apr 12, 2008)

Get a matched motor and controller... Something you don't have to mess with programming and tuning.


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## wind81 (Sep 17, 2011)

dedlast said:


> This is a case where I don't have any personal experience, but everything I've read on here says the vibration will be/should be practically nonexistent.
> 
> Think about it, in an ICE car, for every revolution of the crank, you have a certain number of controlled explosions happening all the time. And then you have to stop and reverse the direction of travel of the mass of all of the pistons every revolution. All of that adds up to lots of bumps and bangs.
> 
> ...


 
Hi dedlast, thanks for your reply. You got your point right. It is very different from internal combustion engine which vibration is very important.


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## wind81 (Sep 17, 2011)

frodus said:


> Get a matched motor and controller... Something you don't have to mess with programming and tuning.


Hi, frodus. Ok i get it. Thanks for your advice! Btw, do you have any good recommendation of AC motor and also controller?


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## frodus (Apr 12, 2008)

email or PM me. I may have something but because you HAVE to use 400V pack, it won't be cheap.


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## wind81 (Sep 17, 2011)

frodus said:


> email or PM me. I may have something but because you HAVE to use 400V pack, it won't be cheap.


Ok, thanks


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