# MOSFET Recommendations for Alternator Controller?



## Salty9 (Jul 13, 2009)

I am planning on building a controller for an alternator to be used as a motor. Info I've found on the web indicates that they can be driven at up to 7KW. 

I would like to build the controller for at least 10KW in order to derate the MOSFETs. 

Does anyone have recommendations for suitable MOSFETs?

Thanks for any input.


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## frodus (Apr 12, 2008)

So you realize you're going to be building a BLDC motor controller with an adjustable field channel? i.e. 7 channels of mosfets and a suitable microcontroller?


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## yarross (Jan 7, 2009)

Salty9 said:


> I've found on the web indicates that they can be driven at up to 7KW.


Uhm. 7KW @ 12V? Or much more volts at high rpm and full excitation?


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## EVMAN (Jul 26, 2007)

Salty9 said:


> I am planning on building a controller for an alternator to be used as a motor. Info I've found on the web indicates that they can be driven at up to 7KW.
> 
> I would like to build the controller for at least 10KW in order to derate the MOSFETs.
> 
> ...


Are U going to use a PM rotor??

If not, then U might need to rewind the rotor to handle higher current.

If using a stock rotor, with stock sliprings, a small PWM is all U'd need for the rotating magnetic field.


Have U found a shematic for the 3-phase drivers??

I'm interested in any non-processor approaches...

afn


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## Salty9 (Jul 13, 2009)

EVMAN,

I'm still in the planning stage and haven't finalized anything yet. Below are 2 threads I have got info from.

http://www.rcgroups.com/forums/showthread.php?t=1123956&highlight=reem

http://endless-sphere.com/forums/viewtopic.php?f=30&t=16328

I want to avoid a PM rotor because I think there are benefits to be gained from a powered rotor. It looks like you get max torque at 0 rpm.

There has been some chat about the claw-hammer rotor being inefficient. If it causes problems, I will consider building a rotor with laminations.


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## EVMAN (Jul 26, 2007)

Good links salty!

Learned that "REEM" = “Reclaimed Externally Excited Motor”

Aren't ALL motors "externally excited"????
U put power in, and it goes round and round...and round ........ 




Salty9 said:


> EVMAN,
> I want to avoid a PM rotor because I think there are benefits to be gained from a powered rotor. It looks like you get max torque at 0 rpm.


ZERO RPM-That's called "locked rotor" condition.
EASY to burn ANY motor out 
An ESC (ElectronicSpeedControl) should sense the current overload and safely shutdown requiring some sort of reset after locked-rotor condition has been removed. Otherwise, U BURN up controllers and/or motor. Curtis controllers do this by dropping to a lower PWM freq which makes it easier to sense the amps and shutdown quickly enough before the MOSFETs liberate the smoke 



Salty9 said:


> EVMAN,
> There has been some chat about the claw-hammer rotor being inefficient. If it causes problems, I will consider building a rotor with laminations.


A PM rotor has just a fixed magnetic field that needs no power.
U cannot do "rotor weakening" to the (magnetic)flux.
The "claw poles" are just a cheap way to make pole pieces for the wound rotor. 
The cylinder/ring PM's that are sold for this cost wayyyy to much.
I agree that a wound rotor offers more possibilities. Cheaper too. 
No exotic mail-order parts.
Since U did not come across a shematic, how about a 555 and a 3phase sequencer?? each phase 120deg apart. One mosfet for each winding of each phase in the alternator. spreads the amps out. 555 controls the speed.

Now back to dinner.....
afn


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## Amberwolf (May 29, 2009)

Salty9 said:


> Does anyone have recommendations for suitable MOSFETs?


Not without a voltage that you're going to run it at. 

There are lots of choices among devices, and many are suitable depending on what kinds of voltages you will be seeing across the DS junction. 

This thread may be helpful, though:
http://endless-sphere.com/forums/viewtopic.php?f=2&t=15606
________
HOW TO ROLL BLUNTS


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## EVMAN (Jul 26, 2007)

Since I can only comment here and not at endless-sphere......

VERY GOOD MOSFET links, amber !! 

Do U have links for MOSFET/IGBT drivers??

I've seen DIY drivers using 555 charge pumps, etc.

I like to stay away from "specialized" chips, cause if U blow them up, U probably don't have one in the spare parts box 

Noticed on endless-sphere U list GateCapacitance. VERY GOOD!
Longer/wider pcb traces ADD to the C and must be accounted for when charging/discharging. 
I've been following Paul&Sabrina's DIY controller. It uses one Micrel(?) gate driver and has long pcb traces.

Again, thanx for the many links!!!


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## Salty9 (Jul 13, 2009)

The discussion here has helped me redefine my requirement parameters (Bureaucratic-speak for I screwed Up)

I've decided to lower my sights initially and just try for a controller that works at 24V and scale-up from there. I'm planning on modular boards so if anything works it can be used down the road.

I will start with Atmel as I have a STK500 already.

Thanks

Chuck


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## Amberwolf (May 29, 2009)

Salty9 said:


> The discussion here has helped me redefine my requirement parameters (Bureaucratic-speak for I screwed Up)


I am quite familiar with the redefinition process.  This occurs constantly on my CrazyBike2 and other projects. 



> I've decided to lower my sights initially and just try for a controller that works at 24V and scale-up from there. I'm planning on modular boards so if anything works it can be used down the road.


Lots and lots of MOSFETs will handle 24V, but you're going to need a lot of them in parallel on each phase for multi-KW drives. 

If the motor you're driving can handle higher voltages, you're far better off with higher voltage to get a higher wattage, since you'll end up with smaller wires and less resistance losses trying to get the power to the motor, both in supply wires and in your battery pack. Plus you can use smaller capacity cells (less cost each) to get the same Wh in the pack, with less Peukert effect on them and so more actual power out to your system. 

Have you considered starting with a "standard" "ebike-type" controller for each part of the motor first? For instance, a regular brushed motor controller for the field winding, and then a BLDC controller (like some of the 18-FET programmable Infineon's that have been beefed up over at Endless Sphere for 100V 100A or more) to run the three phase windings. 




EVMAN said:


> VERY GOOD MOSFET links, amber !!


I am hoping to build a good database there of useful MOSFETs (drivers and such would be good too). 



> Do U have links for MOSFET/IGBT drivers??


Other than the Micrel ones, no, though I have seen quite a few out there for various purposes--most of them are designed for automotive use, to run cooling fans and actuator motors or fluid pumps. Sometimes they are also integrated into whole drive modules including the output power stage. 




> I've seen DIY drivers using 555 charge pumps, etc.
> 
> I like to stay away from "specialized" chips, cause if U blow them up, U probably don't have one in the spare parts box


I have used the Micrel drivers in a couple of attempts at a BLDC controller based around OnSemi MC3303x chips, but so far all I've managed to do is blow up chips due to using perfboard rather than etching PCBs. I can't afford to waste any PCB etchant or materials (or to pay anyone to make them for me) on prototype boards, so I needed to be sure the design would at least work before etching anything. Unfortunately it appears to require a PCB to work at all, so I have yet to make any working BLDC controller, and will probably never do so, as it's cheaper to buy a programmable one for an ebike, and modify it to suit my needs. 

In my 2QD brushed controller it is all transistors except for the quad comparator chip, and it has it's own little transistor charge pump in there that works very well. 

One thing you do want to be sure of is that your gate driver also isolates the power side from the control side as totally as possible. This provides some noise immunity as well as preventing a power side failure from destroying the whole controller. Those Micrel chips are designed to do that.




> Noticed on endless-sphere U list GateCapacitance. VERY GOOD!
> Longer/wider pcb traces ADD to the C and must be accounted for when charging/discharging.
> I've been following Paul&Sabrina's DIY controller. It uses one Micrel(?) gate driver and has long pcb traces.


And if you use perfboard and wiring it is even worse, with lots of inductance and cross-conduction to confuse things further.  Ask me how I know. 
________
Children wellbutrin


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## EVMAN (Jul 26, 2007)

Hey MOSFET users, I just found this little item---

http://www.fairchildsemi.com/pf/FO/FOD3180.html

wow  

I know....very specialized....

Amber,
when perfboarding, think in THREE dimentions 
and..."radially"....


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## yarross (Jan 7, 2009)

EVMAN said:


> Have U found a shematic for the 3-phase drivers??
> 
> I'm interested in any non-processor approaches...


The're lots of BLDC controller ICs from many manufacturers. To use them in this application, one has to complement them with:


Excitation control.
Rotor position sensing.
BLDC controllers typically require coarse, Hall sensor position input just for commutation. This can be done by incorporating Hall sensors into the motor or can be generated from encoder signals. So, a microcontroller may be suitable and it can do other thigs that are required by traction drive controller (ie gas/brake pedal pot sensing, failure detection, contactor control etc).


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## Salty9 (Jul 13, 2009)

I've been thrashing around for 6 months trying to find info on building an alternator controller and I found this:

http://www.diyelectriccar.com/forums/showthread.php/diy-hybrid-brushless-motor-controller-using-23799.html?highlight=dalardan

The only things missing are arrows and signs saying "Start here stupid"


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