| 摘要 |
<p>The control circuit for the electric motor driving a central heating pump comprises inductive components regulating the power delivered to the motor. The inductance (2) provides the main phase for the motor, whilst an inductive impedance (3) mounted in series with a capacitive impedance (4) provides the auxiliary phase. The capacitance (4) comprises two capacitors both of which are used for normal speed operation, and one of which (4a) provides the appropriate capacitance for low speed operation. When the motor is first switched on, a thermistor (5) behaves as a closed switch, and both capacitors are in use providing full power for starting. After heating by the motor current, the resistance of the thermistor increases considerably and so the second capacitance (4b) is effectively taken out of circuit, so that the motor operates at low speed. An override switch (6) is provided for permanent full speed operation.</p> |
