Safety device for a power supply

Inventor: Neil Lindsay (Congewai, AU)

H02H5/105 G01R31/50 G01R31/67 H02H3/335 H02H3/338 H02H9/02 H02H11/002 G01R31/69 H02H3/04

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Quick Facts

Patent No.: US 10,892,614
App. No.: 15/779,506
Granted: Jan 12, 2021
Kind: B2

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Abstract

Safety device for an electrical apparatus powered by an AC mains power supply, the safety device comprising: an electric circuit having inputs for connecting to an active, neutral and earth conductors of the electrical apparatus which are in turn coupled to the AC mains power supply, the circuit being operable to: produce and apply a stepped down voltage and current to the earth conductor from the main supply; and electrically isolate the active and neutral conductors from the earth conductor in response to detecting that either: the active conductor is incorrectly wired to the neutral circuit of the AC mains power supply; the neutral conductor is incorrectly wired to the active circuit of the AC mains power supply; or the neutral conductor is switched; wherein one or more solid state relays are employed by the circuit for both producing the stepped down voltage and electrically isolating the conductors from earth.

Claims (55)

1. A safety device for an electrical apparatus powered by an AC mains power supply having a neutral circuit and an active circuit, the safety device comprising an electrical circuit having active, neutral, and earth terminals for connecting to respective active, neutral, and earth conductors of the electrical apparatus, wherein the electrical circuit comprises:

first and second optocouplers; and

a bipolar transistor,

wherein:

an anode of the first optocoupler is electrically connected to the active terminal via a first electrical pathway;

a collector of the first optocoupler is electrically connected to the active terminal via a second electrical pathway;

a cathode of the first optocoupler is electrically connected to an anode of the second optocoupler via a light emitting diode (LED);

an emitter of the first optocoupler is electrically connected to a collector of the second optocoupler;

a cathode of the second optocoupler is electrically connected to the neutral terminal;

an emitter of the second optocoupler is electrically connected to the earth terminal;

a base of the bipolar transistor is electrically connected to the first electrical pathway;

a collector of the bipolar transistor is electrically connected to an anode of the LED; and

an emitter of the bipolar transistor is electrically connected to a cathode of the LED,

and wherein:

in response to (a) the active conductor being wired to the neutral circuit of the AC mains power supply, (b) the neutral conductor being wired to the active circuit of the AC mains power supply, or (c) the neutral conductor being disconnected from the AC mains power supply, the first and second optocouplers are configured to electrically isolate the active terminal and the neutral terminal from the earth terminal by (i) switching off, or (ii) failing to switch on, and

the bipolar transistor is configured to switch on in response to the first and second optocouplers switching off or failing to switch on, thereby preventing the LED from illuminating to provide a visual indication of a wiring fault.

2. The safety device in accordance with claim 1 , wherein the electrical circuit is integrated into the electrical apparatus.

3. The safety device in accordance with claim 2 , wherein the LED is visible externally of a housing of the electrical apparatus.

4. The safety device in accordance with claim 1 , wherein the first and second optocouplers are miniature optocouplers.

5. The safety device in accordance with claim 1 , wherein in response to the active, neutral, and earth terminals being correctly wired to the AC mains power supply:

the first and second optocouplers are configured switch on, thereby establishing a parallel active to earth circuit and active to neutral circuit, and

the bipolar transistor is configured to switch off in response to the first and second optocouplers switching on, thereby resulting in the LED turning on, thereby indicating that the active, neutral, and earth terminals are correctly wired to the AC mains power supply.

6. The safety device in accordance with claim 1 , wherein the electrical circuit further comprises a resistor network electrically disposed between the active and earth terminals, wherein the resistor network is configured to produce a reduced voltage and current when compared to a voltage and current of the AC mains power supply.

7. The safety device in accordance with claim 1 , wherein the electrical circuit further comprises a magnetically controlled switch electrically disposed between the emitter of the first optocoupler and the collector of the second optocoupler, and wherein the magnetically controlled switch is configured to switch from a closed state in an absence of a magnetic field to an open state in response to a magnet in proximity to the magnetically controlled switch, thereby electrically isolating the active and earth terminals, causing the bipolar transistor to switch on, and preventing the LED from illuminating.

8. A safety device for connecting to an AC mains power supply, the safety device comprising:

an electrical circuit having active, neutral, and earth terminals for connecting to respective active, neutral, and earth conductors of the AC mains power supply, the electrical circuit comprising: