Here's a peek at my homemade power controller - 'Hazen's Power Wheel'.  The maximum overall specs are 200 V and 1350 Amps.  Of course, I am not going to tempt fate by running at 1350 Amps.  As far as I know, this design is unique in this market.  Usually, controllers are 'bread boxes'.  There is nothing wrong with bread boxes - I just wanted to improve on that design.

 

Before I go on, let me state clearly that I found nothing wrong with the Curtis controller that this one replaces.  The Curtis seemed to be a very well built controller and I will keep it for a spare.  The only reason I built my own is because I thought of a new physical design approach for high-power control.

 

As you can see, the above prototype is circular in design.  The circularity offers symmetrical and balanced treatment of drive control, high-current distribution among the power switches (MOSFETs) and even distribution and dissipation of heat.  It is also very easy to service, should the need arise.  As it turns out, the fan that you see mounted on the right side of the controller is really not needed - even so, I am going to keep it as it only draws 0.1 Amp at 12 V.

 

All 15 MOSFETs are mounted evenly spaced around the edge of one of the aluminum discs.  Everything about the design is perfectly symmetrical and balanced.  For high-power applications, this helps ensure equal treatment for all of the power MOSFETs.

 

The current limiting is adjustable over a range of 325 to 1350 A.  Interestingly, I am finding that the performance is just fine at a conservative 325 Amp setting.  Like most controllers, I have a 'watch-dog' circuit that disables the controller and cuts power if the throttle resistor (PB-6) becomes open or disconnected.  I do not have over-temperature protection because these MOSFETs become barely warm.  If an over-temperature event does take place, so be it - I'll repair it and make any circuit changes that might be required.

 

Some have already asked if I am going to start manufacturing and selling Hazen's Power Wheel.  I have no intentions of doing that at this time. There are many great controller choices available in what is already a crowded market. 

 

My hat is off to all of the engineering teams that invested many many hours in design, testing and tweaking to arrive at solid products.  It is not as easy as it might seem.  I have always said that there is a great distance between an idea and a schematic and an even greater distance between the schematic and the actual working prototype.

 

Power Wheel details revealed in Power Electronics Technology Magazine article. Click here!

 

- Mark