초록 ▼

A motor protection circuit for an electric motor driven by a pulse width modulated amplifier. It has a capacitor and a first conduction path connected to a first terminal of the capacitor and connectable to a first conductor. It also has a second conduction path connected to the second capacitor ter

A motor protection circuit for an electric motor driven by a pulse width modulated amplifier. It has a capacitor and a first conduction path connected to a first terminal of the capacitor and connectable to a first conductor. It also has a second conduction path connected to the second capacitor terminal and connectable to a second conductor. There is a DC voltage difference between the first conductor and the second conductor. There is a third conduction path between the first terminal and the second terminal. The third conduction path having a resistance which is lower than the resistance of the first conduction path plus the resistance of the second conduction path. The third conduction path passes through a switch which has an input connection to be opened and closed thereby. The input connection is for receiving a signal indicating a motor overload condition, whereby the capacitor discharge switch is closed when the signal indicates the motor overload condition and the capacitor discharge switch is opened when the signal does not indicate the motor overload condition. A charge on the capacitor increases when the signal does not indicate the motor overload condition and the charge on the capacitor decreases when the signal indicates the motor overload condition. The circuit also has a voltage comparator receiving the voltage of the capacitor. The voltage comparator produces a signal for shutting down the motor.

대표청구항 ▼

[I claim:] [1.](a) a capacitor having a first terminal and a second terminal;(b) a first conduction path connected at one end thereof to said first terminal and connectable at a second end thereof to a first conductor;(c) a second conduction path connected at a first end thereof to said second termi

[I claim:] [1.](a) a capacitor having a first terminal and a second terminal;(b) a first conduction path connected at one end thereof to said first terminal and connectable at a second end thereof to a first conductor;(c) a second conduction path connected at a first end thereof to said second terminal and connectable at a second end thereof to a second conductor, a substantially constant DC voltage difference existing between such second conductor and such first conductor;(d) a third conduction path between said first terminal and said second terminal and having a conduction path resistance lower than a resistance of said first conduction path plus a resistance of said second conduction path, said third conduction path passing through a capacitor discharge switch, said capacitor discharge switch having a switch signal input connection to be opened and closed thereby, said switch signal input connection being connectable to a first digital signal indicating a motor overload condition, whereby said capacitor discharge switch is closed when such first digital signal indicates such motor overload condition and said capacitor discharge switch is opened during an absence of such first digital signal indicating such motor overload condition, so that a charge on said capacitor increases during such absence of first digital signal indicating such motor overload condition and so that said charge on said capacitor decreases when such first digital signal indicates such motor overload condition; and(e) a voltage comparator connected to receive a capacitor voltage from said capacitor, said capacitor voltage being due to said charge on said capacitor, said voltage comparator producing a second digital signal indicating whether said capacitor voltage is below a predetermined voltage level, said second digital signal being communicatable to a shut down switch to shut down such motor.