He gave me a PWM z Alliexpres regulator, max 60V i 20A

Since the early days of the development of electricity and electronics, there has been a need to build regulators to smoothly influence the power dissipated in a load. The first regulators, built as linear regulators, introduced huge losses on the regulating element and, while they worked relatively well for low-power devices (e.g. the speed controller of a tape-shift motor in tape recorders), this was already problematic for medium and high power. This was due to the operation of the power elements in the linear range, much less loss was provided by operation as a key (i.e. open or fully closed with the transient omitted). By controlling the ratio of open to closed time accordingly, it was possible to regulate the power of the load in a smooth manner with minimal losses in the regulator itself. Thus was born the now widely used PWM ( Pulse-Width Modulation ) or Pulse Width Modulation. PWM has found its main application in DC circuits to control the speed (power) of DC motors, heaters or the brightness of light bulbs (traditional as well as LED). The circuit itself, which generates the signal for the actuator, can be implemented in many ways, whether in discrete technology (single transistors) or based on TTL/CMOS digital circuits or even operational amplifiers or specialised PWM controller circuits. It is also easy to implement on probably virtually any microprocessor/microcontroller. One circuit often used as a PWM controller by both amateurs and professionals is the "immortal" NE555.

The described regulator module was given to me by a colleague, who purchased several pieces to regulate the speed of the windscreen wiper motors in his car. The module is packaged in an anti-static foil bag;