Safety circuit for chimney fans
First Claim
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1. A safety circuit for a chimney fan driven by a household current-powered asynchronous motor with an auxiliary winding and a capacitor, comprising:
- means for briefly increasing a supply of voltage to the motor immediately before a brief interruption of the connection between the household current and the capacitor;
means for measuring a signal across the auxiliary winding, and means for causing an alarm indication when the signal is below a preset value.
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Abstract
A single-phase asynchronous motor with an auxiliary winding in which non-rotation is detected by the absence of an induced voltage across the auxiliary winding when it is briefly disconnected from its power source. Before the detection, the motor is briefly provided with a higher operating voltage.
10 Citations
12 Claims
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1. A safety circuit for a chimney fan driven by a household current-powered asynchronous motor with an auxiliary winding and a capacitor, comprising:
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means for briefly increasing a supply of voltage to the motor immediately before a brief interruption of the connection between the household current and the capacitor;
means for measuring a signal across the auxiliary winding, and means for causing an alarm indication when the signal is below a preset value. - View Dependent Claims (2, 3)
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4. A safety device for a chimney fan driven by a household current-powered asynchronous motor with an auxiliary winding and a capacitor, the safety device comprising:
a safety circuit, wherein a voltage supplied to the motor is briefly increased immediately before a brief interruption of the connection between the household current and the capacitor, whereupon a measuring signal is taken across the auxiliary winding, said measuring signal causing an alarm when it is below a preset value. - View Dependent Claims (5, 6)
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7. Method for monitoring a chimney fan driven by a household current-powered asynchronous motor with an auxiliary winding and a capacitor, comprising steps of:
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briefly increasing a voltage supplied to the motor;
immediately after the step of increasing, briefly interrupting a connection between the household current and the capacitor;
measuring a signal across the auxiliary winding during the brief interruption; and
causing an alarm indication when the signal is below a preset value. - View Dependent Claims (8, 9)
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10. A chimney fan system comprising:
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a safety circuit; and
a chimney fan driven by a household current-powered asynchronous motor with an auxiliary winding and a capacitor;
wherein the voltage supplied to the motor is briefly increased immediately before a brief interruption of the connection between the household current and the capacitor, whereupon a measuring signal is taken across the auxiliary winding, said measuring signal causing an alarm indication when it is below a preset value. - View Dependent Claims (11, 12)
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Specification