It is often necessary to reduce the rotational speed of the electric drill or other power tools with brushed AC motor. In most cases, the power regulators are well controlled active load, whereas the regulation of the reactive load has its own characteristics. Usually used or the number of pulse, or the phase of the pulse control principle.
Adequately these issues are reflected in the publications of different years, for example in [1...3].
The proposed scheme provides regulation with feedback on a current collector of the AC motor, whereby when the load increases correspondingly increased torque on the shaft. The scheme was implemented to drive the sewing machine in a production environment. To control the speed of sewing machines used coal (tablet) rheostats, which are very short-lived. The regulator shown in the figure, consists of a power switch SCR VS1, rectifier valves VD1, VD2 and the variable resistor R2 to the control circuit. At the output of the rectifier bridge is provided. All elements of the regulator are mounted on the Board mounted Assembly and covered with a shock resistant casing. Overheating of the SCR was not observed, so it is installed on the mounting rack without heat sink.
Some difficulty is a mechanical unit that transmits the force from the pedal on the axle of the potentiometer, but it can be overcome if to apply the gear sector and pinion.
A characteristic feature of the work of the regulator is its feedback load. By increasing the load increases the torque on the motor shaft. Thanks to this car easily passes the thickening in the form of seams, works more smoothly. Sparking at the collector was observed.
When using the controller for more powerful engines should be selected according to the current of the bridge rectifier and SCR to be installed on the radiator.
Literature
Author: I. Semenov, Moscow region, Dubna; Publication: N. Bolshakov, rf.atnn.ru