Electromagnetic adjuster current controller - has measuring resistor incorporated in lead between power transistor and magnetic coil

摘要

The electromagnetic proportional adjustor has a magnetic coil (7) whose feed current is controlled by a power transistor (1) in dependence on a pulsed voltage, modulated by a comparator (10) for a rated and actual value voltage. In the lead (6) between the power transistor and the magnetic coil is incorporated a measuring resistor (3), with a freewheel diode (19) in parallel to the coil and resistor. The resistor terminal on the power transistor side is coupled to the non-inverting input (25) of an operational amplifier (34) via a resistor (20) of a voltage divider. On the coil side, the measuring resistor terminal is coupled to the inverting input (24) of the rectifier via a series resistor (21). The amplifier output (26) is coupled to its inverting input via a push-pull resistor (23), and to a nodal point, coupled to a voltage divider second resistor (22) via an output resistor (27). USE/ADVANTAGE - For car servo-steering etc., with protection of measuring resistor against destruction by connecting faults.