| 摘要 |
An improved capacitive braking system is provided for fractional Horsepower induction motors in home appliances, for example in a food processor of the type having a working bowl mounted on a housing containing the induction motor, with a shaft in the bowl for removably supporting a rotary food processing tool to be driven by the induction motor. The new braking system rapidly halts the coasting motion of the motor rotor and tool after the motor has been disconnected from the electric power line. A first switch is provided to control the application of electrical energy to the induction motor for sustained operation, and a second "pulse" switch is provided to control the application of electrical energy to the induction motor for brief surges of momentary operation. The braking system includes a second capacitor which is external to the induction motor and distinct from the starting capacitor normally associated with an induction motor. In the preferred embodiment, this second capacitor becomes connected in circuit with the windings of the induction motor to provide an enhanced braking effect upon disconnection of the induction motor from the electric power, said second capacitor having a capacitance larger than that of the starting capacitor for producing a resonant magnetic field braking action on the coasting rotor. The first and second switches are advantageously arranged and interconnected so that it is not possible inadvertently to connect either capacitor across the line voltage, thus avoiding the possible destruction of the capacitors by the line voltage, regardless of the order in which the switches are actuated by the user. |
