I am demonstrating a soft-starter for a technical report, and I am having trouble finding the correct motor and power source.
I want to use SCRs in a reverse-parallel configuration to limit the in-rush current and torque. The problem is that this soft-start setup would require a 3-phase voltage supply, along with a 3-phase induction motor, which is quite costly for an experiment.
My question is would I be able to demonstrate a soft-start of a motor by using a single phase AC source? OR is there a better way to demonstrate this experiment besides using the reverse-parallel setup?
Best Answer
For your experiment, I presume that you want to demonstrate peak current with and without your soft starter. I'd start with a low voltage DC motor, a fixed flywheel mass, a current shunt, and possibly a speed sensor. You'll also want a fixed voltage power supply with a low source impedance and adequate peak current; a battery will also work.
The flywheel attached to the shaft will extend the "area under the curve" so that your measurements can be done slightly more leisurely. Without it, the motor might go from full stop to full speed too quickly to measure repeatably. The speed sensor may be helpful to compare current at particular shaft velocities, and also to indicate when terminal velocity has been reached.
The DC motor can be driven with 1) a low-impedance DC source to show peak current without limiting 2) a plain resistor current limiter (though top speed will be reduced) and 3) solid state current limiting, presumably doing cycle-by-cycle limiting or whatever your project requires.