25 years as a mechanical & aerospace engineer has finally caught up with me; I guess I have gotten a little rusty with electrical engineering.
I need a lightweight solution to power a 18VDC electric motor from 0 to 25 amps via 120VAC. Lightweight means no transformers and small inductors and caps. I don't think a simple chopper circuit would work since I don't think the insulation on the 18VDC motor can handle the ~170 V peak coming from a bridge rectifier.
As a test: I placed four 10mH chokes in series between a bridge rectifier and the motor. Since the chokes were rated for 5 amps, I used a variable transformer to keep the voltage and current down. This arrangement reduces the voltage on the motor some during high amps, but the voltage is too high at low amps.
I think I need to build a PWM to increase the frequency to 1000 hz or more and reduce inductor size, but I also need a way of automatically maintaining 18 to 25 volts on the motor when the amp draw is low.
BTW: I found AVR for generators were either too expensive, too little current, or too heavy.
Any help with the PWM and voltage regulator circuits would GREATLY by appreciated.
I need a lightweight solution to power a 18VDC electric motor from 0 to 25 amps via 120VAC. Lightweight means no transformers and small inductors and caps. I don't think a simple chopper circuit would work since I don't think the insulation on the 18VDC motor can handle the ~170 V peak coming from a bridge rectifier.
As a test: I placed four 10mH chokes in series between a bridge rectifier and the motor. Since the chokes were rated for 5 amps, I used a variable transformer to keep the voltage and current down. This arrangement reduces the voltage on the motor some during high amps, but the voltage is too high at low amps.
I think I need to build a PWM to increase the frequency to 1000 hz or more and reduce inductor size, but I also need a way of automatically maintaining 18 to 25 volts on the motor when the amp draw is low.
BTW: I found AVR for generators were either too expensive, too little current, or too heavy.
Any help with the PWM and voltage regulator circuits would GREATLY by appreciated.