High current, three-phase

These sheilds are not working in a linear region, they are switching the output either all on or all off so power is really only dissipated during the transision (It works as a switch)

when a MOSFET (The switching device) is on, it has a resistance measures in milli ohms so even 10Amps will only dissipate 10 - 100mW. obviously when off, there is no current and therefor no power disspiation

As you hae already noted, using PWM is how the "Average" voltage is varied

now for current limiting, a sense resister in the power circuit measures the current in the motor and when it reaches a preset value, will turn off the switch . because the load is inductive, the current is not instantly I=V/R, it builds up over time allowing the control circuit to limit the current but still provide the power to the motor.

This is also how modern stepper motor drivers work. I am currently working with NEMA23 Steppers that are rated at 3V and 2.9Amps but the supply is 48V @ 10Amps, the system relies on the properties of an inductor to be able to control the power and not fry the motor

Hope this helps

Thank you for your answer Peter!

I think I have understood more or less.

I just want to have three signals with different phase. My motor is a linear induction motor, and there is any danger for my coils to fry. I want to have constantly through my coils a signal that will be maximum 10Amps. I am thinking on using maybe an ESC (used for brushless motors) but they use the position of the roto to work. I find the same problem with other standard systems used for commercial motors (brushless, induction). Do you know any commercial device that will give me a three-phase signal whose amplitude and frequency I can manage?

Drives - Motor Speed AC | Farnell element14

Nice one Paul, you beat me to it,

I was about to suggest VFDs (Variable Frequency Drives)

I dont know what the motor Power / Voltage is yet but your suggestions should cover any Mains rated motors for sure

You could re-programm an ESC. Some are atmel based. Look for blheli AS an example.

Thank you all for your answers!

I though about VFDs, but what I don't like about them is that they are big and not easy to manipulate. I want to have something more flexible, whose output can be controlled digitally: I will have to control the intensity with the position of the aluminium plate that will move upon the motor.

I like the idea of the ESC. But I think they use the position of the rotor to work, don't they? (with a Hall sensor or back emf the get the position) Do you know if we can reprogram it and make it work? I am gonna try to do it with an autoquad ESC32 I have.

Thank you everyone for your answers again!

All Hobby ESCs I know use back EMF. The Autoquad ESC is based on a STM32F103. Firmware source is on github. Instrucions how to flash.

Basically the ESC does the same thing as Robert Peter Oakes described earlier.