Safety circuit for chimney fans

• US 20040112370A1
• Filed: 10/24/2003
• Published: 06/17/2004
• Est. Priority Date: 12/12/2002
• Status: Active Grant

• Current Assignee: Exhausto A/S (Aldès SA)
• Original Assignee: Exhausto A/S (Aldès SA)
• Inventors: Brandt, Henning
• Granted Patent: US 6,959,706 B2
• Time in Patent Office: Days
• US Class Current: 126/299R
• CPC Class Codes: F23L 17/005 using fans
• CPC Class Codes: F23N 2231/04 for electrical power failures
• CPC Class Codes: F23N 2231/20 Warning devices
• CPC Class Codes: F23N 2233/04 with variable speed

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.

Claims

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.

2. A safety circuit according to claim 1, wherein the means for briefly increasing is performed in conjunction with an electronic speed control for the motor by briefly setting the speed control to maximum.

3. A safety circuit according to claim 1, further comprising means for combining information about the presence of household voltage with information about a current in the motor circuit in order to ascertain if a blocked motor shaft has occurred when the alarm is indicated.

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.

5. A safety circuit according to claim 4 in conjunction with an electronic speed control for the motor, wherein the speed control is briefly set to maximum immediately before the brief disconnection in order to obtain the measuring signal.

6. A safety circuit according to claim 4, wherein in case of alarm, information about the presence of household voltage is combined with information about a current in the motor circuit in order to ascertain if a blocked motor shaft has occurred.

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:

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.

8. The method of claim 7, wherein the step of briefly increasing the voltage is performed in conjunction with an electronic speed control for the motor by briefly setting the speed control to a maximum level.

9. The method of claim 7, further comprising a step of combining information about the presence of household voltage with information about a current in the motor circuit in order to ascertain if a blocked motor shaft has occurred when the alarm is indicated.

10. A chimney fan system comprising:

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.

11. The chimney fan system of claim 10 further comprising an electronic speed control for the motor, wherein the speed control is briefly set to maximum immediately before the brief disconnection in order to obtain the measuring signal.

12. The chimney fan system of claim 10, wherein in when the alarm is indicated, information about the presence of household voltage is combined with information about a current in the motor circuit in order to ascertain if a blocked motor shaft has occurred.