| 摘要 |
The motor(M) is fed from a reversible supply(CM,Q) via a pnp(T4) or npn(T2) transistor, according to direction, with thermal protection from diode-selected(D1,D2) termistance(Th1,Th2). On overload, current rise in a series resistor(R3) raises the base voltage(U3) in two similarly opposed transistors(T3,T1), causing current flow in one of two resistances(R1,R2) interconnecting the collectors of the associated transistor pair(T3,T4;T1,T2). This is thermally coupled(21,20) to the selected thermistance. the additional heat accelerates the latter's protective action, already initiated directly by the overcurrent. On supply interruption, motor-generated voltage circulates current through the previously idle transistor(T4 or T2), its associated resistor(R2 or R1) and the transistor of the other pair(T3 or T1), braking the motor and attenuating induced overvoltages. |
