Transfer switch for automatically switching neutrals for one or more loads between two electrical sources of power

• US 9,509,139 B1
• Filed: 12/28/2011
• Issued: 11/29/2016
• Est. Priority Date: 12/28/2010
• Status: Active Grant

• Current Assignee: Reliance Controls Corporation
• Original Assignee: Reliance Controls Corporation
• Inventors: Flegel, Michael O.
• Primary Examiner(s): Amrany, Adi
• Application Number:
  US13/339,069
• Time in Patent Office: 1,798 Days
• Field of Search: 307112-116, 307/44, 307 64- 66, 307/125, 307/130
• US Class Current: 1/1
• CPC Class Codes: H02J 3/00 Circuit arrangements for ac mains or ac distribution networks
• CPC Class Codes: H02J 9/066 characterised by the use of dynamo-electric machines H02J9/08 takes precedence

Abstract

A method and system for selectively controlling the supply of electrical power to an electrical panel that is capable of receiving electrical power from more than one power source, such as a utility power supply and an auxiliary power supply, e.g., an electrical generator, prevents the neutral conductor of the electrical panel from being connected to one power supply when the hot conductors of the electrical panel are connected to another power supply.

Claims

1. An apparatus connectable to a transfer switch panel for automatically connecting neutrals of one or more loads to either a neutral of a first power source or a neutral of an alternate power source, wherein the transfer switch panel includes a transfer switch having a first input configured to receive power from one of a first hot conductor and a second hot conductor from the first power source, a second input configured to receive power from one of a first hot conductor and a second hot conductor from the alternate power source, and an output configured to conduct power from the first power source when the output is connected to the first input and to conduct power from the second power source when the output is connected to the second input, the apparatus comprising:

a load side neutral conductor that connects to the neutrals of the one or more loads;

a first neutral conductor that connects to the neutral of the first power source;

a second neutral conductor that connects to the neutral of the alternate power source;

a first electrical conductor that connects to either the first hot conductor or the second hot conductor from the first power source that is not connected to the first input of the transfer switch;

a second electrical conductor that connects to the output of the transfer switch;

a third electrical conductor that connects to either the first hot conductor or the second hot conductor from the alternate power source that is not connected to the second input of the transfer switch; and

a switch that connects the load side neutral conductor to the first neutral conductor when a voltage potential between the first electrical conductor and the second electrical conductor is greater than a voltage potential between the second electrical conductor and the third electrical conductor, and connects the load side neutral conductor to the second neutral conductor when the voltage potential between the second electrical conductor and the third electrical conductor is greater than the voltage potential between the first electrical conductor and the second electrical conductor.

2. The apparatus of claim 1 wherein the switch includes an armature movable between a first position in which the load side neutral conductor is connected to the first neutral conductor and a second position in which the load side neutral conductor is connected to the second neutral conductor.

3. The apparatus of claim 2 wherein the switch has at least one coil, and wherein when the first power source is providing power to the transfer switch, the at least one coil is controlled to move the armature to the first position and when the alternate power source is providing power to the transfer switch, the at least one coil is controlled to move the armature to the second position.

4. The apparatus of claim 3 wherein the at least one coil moves the armature to the first position when the voltage potential between the first electrical conductor and the second electrical conductor is 240 volts and moves the armature to the second position when the voltage potential between the third electrical conductor and the second electrical conductor is 240 volts.

5. The apparatus of claim 1 wherein the switch includes a first coil, a second coil, and an armature movable between a first position and a second position, and wherein when the first power source is providing power to the transfer switch, the first coil is energized to move the armature to the first position and when the alternate power source is providing power to the transfer switch, the second coil is energized to move the armature to the second position.

6. The apparatus of claim 1 further comprising a microprocessor that measures the voltage potentials between the first electrical conductor and the second electrical conductor and between the second electrical conductor and the third electric conductor, and provides a command signal to the switch to connect the load side neutral conductor to either the first neutral conductor or the second neutral conductor.

7. The apparatus of claim 6 further comprising a first sensor that provides a first logic signal indicating an operational status of the first power source, a second sensor that provides a second logic signal indicating an operational status of the alternate power source, and wherein the microprocessor receives the first logic signal and the second logic signal, and provides a switching signal to the switch.

8. The apparatus of claim 7 wherein the first sensor measures a voltage potential between the first electrical conductor and the second electrical conductor and the second sensor measures a voltage potential between the second electrical conductor and the third electric.

9. The apparatus of claim 8 wherein:

the first sensor provides a logic HIGH signal when the voltage potential between the first electrical conductor and the second electrical conductor is 240 volts and provides a logic LOW signal when the voltage potential between the first electrical conductor and the second electrical conductor is 0 volts; and

the second sensor provides a logic HIGH signal when the voltage potential between the second electrical conductor and the third electrical conductor is 240 volts and provides a logic LOW signal when the voltage potential between the second electrical conductor and the third electrical conductor is 0 volts.

10. An apparatus usable with a transfer switch panel for automatically connecting neutrals of one or more loads to either a neutral conductor of a first power supply or a neutral conductor of a second power supply, wherein the transfer switch panel includes a transfer switch having a first input configured to receive power from one of a first hot conductor and a second hot conductor from the first power supply, a second input configured to receive power from one of a first hot conductor and a second hot conductor from the alternate power supply, and an output configured to conduct power from the first power supply when the output is connected to the first input and to conduct power from the second power supply when the output is connected to the second input, the apparatus comprising:

a load side neutral conductor that connects to the neutrals of the one or more loads;

a switch that either connects the load side neutral conductor to the neutral conductor of the first power supply or connects the load side neutral conductor to the neutral conductor of the second power supply;

a first sensor sensing a first voltage potential between either the first hot conductor or the second hot conductor from the first power supply that is not connected to the first input of the transfer switch and the output of transfer switch and providing a first logic signal corresponding to the first voltage potential;

a second sensor sensing a second voltage potential between either the first hot conductor or the second hot conductor from the second power supply that is not connected to the second input of the transfer switch and the output of transfer switch and providing a second logic signal corresponding to the second voltage potential; and

a microprocessor that receives the first logic signal and the second logic signal, and in response thereto provides a switching signal to the switch to connect the load side neutral conductor to the neutral conductor of the first power supply when the first logic signal indicates the first power supply is connected to the output of the transfer switch and to connect the load side neutral conductor to the neutral conductor of the second power supply when the second logic signal indicates the second power supply is connected to the output of the transfer switch.

11. The apparatus of claim 10 wherein:

the first sensor provides a logic HIGH signal when the first voltage potential is 240 volts and provides a logic LOW signal when the first voltage potential is 0 volts; and

the second sensor provides a logic HIGH signal when the second voltage potential is 240 volts and provides a logic LOW signal when the second voltage potential is 0 volts.

12. A method of selectively connecting one of a neutral conductor of a first power source and a neutral conductor of a second power source to a load neutral bus, the method comprising the steps of:

monitoring a first voltage potential between one of a first hot conductor and a second hot conductor from the first power source and an output of the transfer switch, wherein;

a first input of the transfer switch is configured to receive power from one of theft first hot conductor and the second hot conductor from the first power source,

the first voltage potential is monitored between either the first hot conductor or the second hot conductor from the first power source that is not connected to the first input of the transfer switch, and

the output is configured to conduct power from the first power source when the output is connected to the first input;

monitoring a second voltage potential between one of a first hot conductor and a second hot conductor front the second power source and the output of the transfer switch, wherein;

a second input of the transfer switch is configured to receive power from one of the first hot conductor and the second hot conductor from the second power source,

the second voltage potential is monitored between either the first hot conductor or the second hot conductor from the second power source that is not connected to the second input of the transfer switch, and

the output is configured to conduct power from the second power source when the output is connected to the second input;

connecting the load neutral bus to the neutral conductor of the first power source when the first voltage potential is greater than the second voltage potential, indicating the first power source is connected to the output of the transfer switch; and

connecting the load neutral bus to the neutral conductor of the second power source when the second voltage potential is greater than the first voltage potential, indicating the second power source is connected to the output of the transfer switch.

13. The method of claim 12 wherein:

a switch apparatus is used to connect one of the neutral conductor of the first power source and the neutral conductor of the second power source to the load neutral bus;

the step of connecting the load neutral bus to the neutral conductor of the first power source includes energizing a first coil in the switch apparatus to move an armature to a first position, wherein the first coil is energized by the first voltage potential; and

the step of connecting the load neutral bus to the neutral conductor of the second power source includes energizing a second coil in the switch apparatus to move the armature to a second position, wherein the second coil is energized by the second voltage potential.

14. The method of claim 12 wherein:

a switch apparatus including a first sensor, a second sensor, a microprocessor, and an actuator is used to connect one of the neutral conductor of the first power source and the neutral conductor of the second power source to the load neutral bus;

the step of monitoring the first voltage potential includes measuring the first voltage potential with the first sensor and transmitting a signal corresponding to the first voltage potential from the first sensor to the microprocessor;

the step of monitoring the second voltage potential includes measuring the second voltage potential with the second sensor and transmitting a signal corresponding to the second voltage potential from the second sensor to the microprocessor;

the step of connecting the load neutral bus to the neutral conductor of the first power source includes generating a control signal to the actuator from the microprocessor to place the actuator in a first position; and

the step of connecting the load neutral bus to the neutral conductor of the second power source includes generating a control signal to the actuator from the microprocessor to place the actuator in a second position.