I need a circuit to achieve constant speed of a customised DC motor as the mechanical load on the motor keeps changing. So, the circuit will have a speed feedback from speed sensor mounted on the motor. Motor is rated at low voltage of 12volts and high current of 100amps. Anything close available in the market? Or how do I build one?
It might be helpful to characterize your current requirements a bit more closely, in terms of whether or not that 100A rating is on a continuous or surge basis, and whether the nature of the load in your application will actually result in a current draw of that magnitude.
For simplicity’s sake, I’d suggest looking at motor controllers designed for use in the FIRST robotics competitions, of which Digi-Key P/N 1286-1226-ND is an example. They’re generally rated for around 60A continuous/100peak, and are intended to let high school students achieve various motion control functions (speed control, position control, etc.) using brushed DC motors in that size range. The controllers themselves are fairly robust, and documentation is pretty widely available as a result.