- #1
RJK
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Last year I built an electric car. I converted a 1966 MG to electric using 8 led acid batteries (96V bus), a DC motor coupled to the transmission, and a large motor controller. The vehicle was working fine. Top speeds of 55 mpg, but with many led acid vehicles, only a 20 miles range. The DC motor controller is a Kelly, purchased from China, and now sems to be disfunctional. It is also limited to the 96V I have. I would like to get this vehicle operational again with more capacity and without spending too much. This is where I need some help.
I was wondering if I could build my own PWM motor controller. There are plenty of small PWM motor controllers around, but I need to control hundreds of amps. I also need some current limit protection (I do have a fusable link, but the drive ought to limit prior to that). The idea I have is to use a low end DC motor controller (many on the market for about $100 or less), then take the output stage and connect it to the gate of a large SCR. The SCR would of course be a series connection between the 96V (or higher) bus and the DC motor.
For current limiting I have a current monitor device that is in line with the 96V bus that is fed to my on board PLC. I use a small touch screen to display battery voltage, RPM, temperature, and running current (among other things). I could put a setpoint on the touch screen and when the current exceeds that simply take a PLC output and tie it to the inhibit line of the small DC controller.
I think I have the basics covered, but my biggest question is how exactly to connect the output stage of the small PWM controller to the gate of the SCR. The device I am looking at is a Digi number ST330S04P0-ND, good for 520A RMS and 400V. I could then add another couple led acid cells for a 120V bus for better performance and range.
I would appreciate input about this idea, and specifically how to make the PWM connection from a small DC drive to a large SCR.
Thanks,
Roger
I was wondering if I could build my own PWM motor controller. There are plenty of small PWM motor controllers around, but I need to control hundreds of amps. I also need some current limit protection (I do have a fusable link, but the drive ought to limit prior to that). The idea I have is to use a low end DC motor controller (many on the market for about $100 or less), then take the output stage and connect it to the gate of a large SCR. The SCR would of course be a series connection between the 96V (or higher) bus and the DC motor.
For current limiting I have a current monitor device that is in line with the 96V bus that is fed to my on board PLC. I use a small touch screen to display battery voltage, RPM, temperature, and running current (among other things). I could put a setpoint on the touch screen and when the current exceeds that simply take a PLC output and tie it to the inhibit line of the small DC controller.
I think I have the basics covered, but my biggest question is how exactly to connect the output stage of the small PWM controller to the gate of the SCR. The device I am looking at is a Digi number ST330S04P0-ND, good for 520A RMS and 400V. I could then add another couple led acid cells for a 120V bus for better performance and range.
I would appreciate input about this idea, and specifically how to make the PWM connection from a small DC drive to a large SCR.
Thanks,
Roger