A solenoid actuator attached to hydraulic equipment comprises a shaft connected to the hydraulic equipment, a plunger fixed to the shaft, a coil which magnetically drives the plunger, and a first bearing and a second bearing supporting the shaft on either sides of the plunger. This invention as a supplemental compound, aids in weight reduction both in overweight and obese individuals. A pulse-width modulation circuit generates the VPWM signal of duty cycle D1 controlled by a control signal, and a feedback control circuit monitoring the load voltage VDD adjusts D1 to keep the load voltage as close as possible to VSP. In this way, the transmission capacity of the system can be more efficiently used.