CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and claims the benefit of U.S.

Patent Application Serial No. 13/787,061 , filed March 6, 2013, which is incorporated by reference herein.

BACKGROUND

Field

The disclosed concept relates generally to display units, and in particular, to display units configured to display trip information. The disclosed concept also relates to circuit interrupters including a display unit configured to display trip information.

Background Information

Circuit interrupters, such as circuit breakers, are generally old and w ell known in the art. Circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high level short circuit or fault condition. In small circuit breakers, commonly referred to as miniature circuit breakers, used for residential and light commercial applications, such protection is typical ly provided by a thermal-magnetic trip device. This trip device includes a bimetal, which heats and bends in response to a persistent overcurrent condition. The bimetal, in turn, unlatches a spring powered operating mechanism, w hich opens the separable contacts of the circuit breaker to interrupt current flow in the protected power system.

Industrial circuit breakers often use a circuit breaker frame, which houses a trip unit. See, for example, U.S. Patent Nos. 5,910,760 and 6, 144,271 . The trip unit may be modular and may be replaced, in order to alter the electrical properties of the circuit breaker.

It is well known to employ trip units which utilize a microprocessor to detect various types of ov ercurrent trip conditions and provide various protection functions, such as, for example, a long delay trip, a short delay trip, an instantaneous trip, and/or a ground fault trip. The long delay trip function protects the load served by the protected electrical system from overloads and/or overcurrents. The short delay trip function can be used to coordinate tripping of downstream circuit breakers in a hierarchy of circuit breakers. The instantaneous trip function protects the electrical conductors to which the circuit breaker is connected from damaging overcurrent conditions, such as short circuits. As implied, the ground fault trip function protects the electrical system from faults to ground.

The earliest electronic trip unit circuit designs utilized discrete components such as transistors, resistors and capacitors.

More recently, designs, such as disclosed in U.S. Patent os.

4,428,022 and 5,525,985, have included microprocessors, which provide improved performance and flexibi lity. These digital systems sample the current waveforms periodically to generate a digital representation of the current. The microprocessor uses the samples to execute algorithms, which implement one or more current protection curves.

When diagnosing field issues with a circuit interrupter, the cause of the trip and other information (e.g., without limitation, each phase current and the ground current at the time of the trip) are beneficial in diagnosing the issue. It is known to employ a liquid crystal display unit in conjunction with a circuit interrupter to display the cause of trip and other information. The liquid crystal display unit employs a battery or a rechargeable battery as a secondary power source in order to maintain the display of the cause of trip and other information during a circuit interruption. This is because the circuit interrupter loses its pow er source during a circuit interruption. How ever, batteries, even rechargeable ones, have a limited lifespan and must be periodically replaced, thus adding to the maintenance cost of the known liquid crystal display unit.

There is room for improvement in circuit interrupters.

There is also room for improvement in display units for use with circuit interrupters.

SUMMARY

These needs and others are met by embodiments of the disclosed concept, which provide a display unit including a memory display configured to display trip information. These needs and others are also met by embodiments of the disclosed concept, which provide a display unit including a bi-stable display configured to display trip information. These needs and others are also met by embodiments of the disclosed concept, which provide a circuit interrupter including a display unit having a memory display configured to display trip information. These needs and others are also met by embodiments of the disclosed concept, which prov ide a circuit interrupter including a display unit hav ing a bi -stable display configured to display trip information.

In accordance with aspects of the disclosed concept, a display unit is configured for use with a circuit interrupter which outputs a trip notification, trip information, and direct current power to the display unit. The display unit comprises: a processor hav ing a routine; a secondary power source configured to output secondary power; a memory display configured to receiv e the direct current power or the secondary power; and a power source selection circuit configured to switch the memory display from the direct current power to the secondary power in response to the display unit receiving the trip notification, wherein the routine of the processor is structured to control the memory display to display the trip information in response to the display unit receiv ing the trip notification.

In accordance with other aspects of the disclosed concept, a display unit is configured for use with a circuit interrupter which outputs a trip notification, trip information, and direct current power to the display unit. The display unit comprises: a processor having a routine; and a bi -stable display, wherein the routine of the processor is structured to control the bi-stable display to display the trip information in response to the display unit receiving the trip notification.

In accordance with other aspects of the disclosed concept, a circuit interrupter configured to protect a power circuit comprises: an electronic trip unit configured to control interruption of the power circuit and to output a trip notification and trip information; a power supply configured to convert alternating current power from the power circuit to a direct current power; a display unit configured to receive the trip notification, the trip information, and the direct current power, the display unit comprising: a processor having a routine; a secondary power source configured to output secondary power; a memory display configured to receive the direct current power or the secondary power; and a power source selection circuit configured to switch the memory display from the direct current power to the secondary power in response to the display unit receiving the trip notification, wherein the routine of the processor is structured to control the memory display to display the trip information in response to the display unit receiving the trip notification.

In accordance with other aspects of the disclosed concept, a circuit interrupter configured to protect a power circuit comprises: an electronic trip unit configured to control interruption of the power circuit and to output a trip notification and trip information: a power supply configured to convert alternating current power from the power ci cuit to a direct current power; a display unit configured to receive the trip notification, the tri information, and the direct current power, the display unit comprising: a processor having a routine; and a bi -stable display, wherein the routine of the processor is structured to control the bi -stable display to display the trip information in response to the display unit receiving the trip notification.

BRIEF DESCRIPTION OF THE DRAWINGS

A full understanding of the disclosed concept can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:

Figure 1 is a schematic diagram in block form of a circuit interrupter in accordance with an example embodiment of the disclosed concept;

Figure 2 is a schematic diagram in block form of a circuit interrupter coupled with a display unit in accordance with another embodiment of the disclosed concept;

Figures 3-6 are schematic diagrams in block form of display units in accordance with other embodiments of the disclosed concept; and

Figure 7 is a front elevation view of a portion of a circuit interrupter having a display unit coupled thereto in accordance with embodiments of the disclosed concept.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Directional phrases used herein, such as, for example, left, right, front, back, top, bottom and derivatives thereof, relate to the orientation of the elements show n in the draw ings and are not limiting upon the claims unless expressly recited therein. As employed herein, the statement that two or more parts are

"coupled" together shall mean that the parts are joined together cither directly or joined through one or more intermediate parts.

As employed herein, the term "number" shall mean one or an integer greater than one (i.e., a plurality ).

As employed herein, the term "processor" shall mean a programmable analog and/or digital device that can store, retrieve and process data; a controller; a control circuit; a computer; a workstation; a personal computer; a microprocessor; a microcontroller; a microcomputer; a central processing unit; a mainframe computer; a mini-computer; a server; a networked processor; or any suitable processing device or apparatus.

As employed herein, the term "energy harvesting component" shall mean a component (or components) which is able to harvest electrical power from a non-electrical energy (e.g., without limitation, solar energy; thermal energy; wind energy; kinetic energy).

As employed herein, the term "memory display" shall mean a display in which pixels of the display operate similar to memory cells. More part icularly, once information is written to a pixel, that information is retained in the pixel until it is rewritten. Memory displays require relatively very little power (e.g., without limitation, microwatts) to maintain a display of information.

As employed herein, the term "bi-stable display" shall mean any one of the class of displays that maintain a display of information without power. Examples of types of bi-stable displays include, without limitation, nematic liquid crystal, polymer stabi lized cho lest eric l iquid crystal, and electrophoretic ink ("E-ink") displays.

Referring to Figure 1 , a circuit interrupter 100 (e.g., without limitation, a circuit breaker), is shown. The circuit interrupter 100 is configured to protect a pow er circuit including a power source 1 and a load 2. The circuit interrupter 100 includes separable contacts 102, an operating mechanism 104 structured to open and close the separable contacts 102, and an electronic trip unit 106 which cooperates with the operating mechanism 104 to trip open the separable contacts 1 02. The circuit interrupter 100 further includes a power supply 108 which converts a portion of alternating current flowing through the power circuit to direct current power VDD- The direct current power VDD is used by digital components included in the circuit interrupter 100.

The circuit interrupter 100 also includes a display unit 1 10. The display unit 1 10 is communicatively coupled with the electronic trip unit 106. The display unit 1 10 receives a trip notification and trip information from the electronic trip unit 106. The trip notification is an indication that the electronic trip unit 106 has caused the operating mechanism 1 04 to trip open the separable contacts 102. In some embodiments the trip notification is, without limitation, a transition of a signal from high to low. The trip information is information regarding the trip (e.g., without limitation, the cause of the trip). The display unit 1 10 can also receive circuit interrupter setting information (e.g., without limitation; full load ampere setting ("Ir"); long delay time ("LDT"); short delay pickup ("SDPU"); short delay time ("SDT"); ground fault time ("GFT")) and/or circuit interrupter diagnostic information (e.g., without limitation; over temperature protection set point; prev ious cause of trips; battery life: tri actuator voltage; trip actuator integrity: contact integrity; trip current magnitudes) from the electronic trip unit 1 06. The display unit 1 10 also receives the direct current power V _D D output by the power supply 108.

The display unit 1 10 is configured to display the trip information in response to receiving the trip notification. Additionally, the display unit 1 10 is configured to continue to display the trip information after the power supply 108 has stopped providing the direct current power V _D D- The display unit 1 10 can also display the circuit interrupter setting information and/or the circuit interrupter diagnostic information. Example display units 31 0,41 0,51 0,610 are illustrated in Figures 3-6 and will be described in more detail hereinafter.

In the example embodiment of the disclosed concept depicted in Figure 1 , the display unit 1 10 is installed in the circuit interrupter 100. Referring now to Figure 2, a display unit 2 10 is configured for use with a circuit interrupter 100', rather than installed in it. The circuit interrupter 100' and the display unit 2 10 are communicatively coupled via an interface 300. The interface 300 may include, for example and without l imitation, a test port of the circuit interrupter 100'. The display unit 2 10 receives a trip notification, trip information, and direct current power VDD from the circuit interrupter 100' via the interface 300. The display unit 210 can also receive circuit interrupter setting information and/or the circuit interrupter diagnostic information via the interface 300.

The display unit 210 is configured to display the trip information in response to receiving the trip notification. Additionally, the display unit 2 10 is configured to continue to display the trip information after the power supply 108 has stopped providing the direct current power VDD- The display unit 2 10 can also display the circuit interrupter setting information and/or the circuit interrupter diagnostic information.

Figure 3 shows another example display unit 3 10 that is configured to receive direct current power VDD, data (e.g., without limitation; trip information; circuit interrupter diagnostic information; circuit interrupter setting information ), and a trip notification. The display unit 3 10 includes a power source selection circuit 3 12, a secondary power source 3 14, a processor 3 16, and a memory display 3 1 .

The power source selection circuit 3 12 is configured to receive the direct current power VDD and the trip notification. The power source selection circuit 3 1 2 is also electrically connected to the secondary power source 3 14 and the memory display 3 1 8. Prior to receiving the trip notification, the power source selection circuit 3 12 allow s the memory display 3 18 to be powered by the direct current pow er VDD- The example secondary power source 3 14 includes a capacitor Ci and a resistor R i . Prior to receiv ing the trip notification, the power source selection circuit 3 12 allows the capacitor Ci to be charged by the direct current power V _D D-

When the power source selection circuit 3 12 receives the trip notification, the power source selection circuit 3 1 2 switches the memory display 3 1 8 from the direct current power VDD to the secondary power source 3 14. The secondary power source 3 14 prov ides the memory display 3 1 8 with power stored in the capacitor C _\ until the capacitor C\ is sufficiently discharged.

The display unit 3 10 also includes a processor 3 16 which receives the direct current power V _D D, the data, and the trip notification. The processor 3 16 includes a routine which is structured to control the memory display 3 1 8 to display the trip information in response to receiving the trip notification. The routine of the processor 3 16 can also control the memory display 3 18 to display the circuit interrupter setting information and/or the circuit interrupter diagnostic information.

The memory display 3 18 requires relatively very l ittle power to maintain display of information. Power supplied by the capacitor C i allows the memory display 3 18 to maintain display of the trip information for an appreciable amount of time (e.g., without limitation, about 2 hours). It will be appreciated by those having ordinary skill in the relevant art that variations in the size of the capacitor Ci will affect the amount of time that the memory display 3 18 can continue to display the trip information after a trip. It will also be appreciated that any suitable size capacitor C\ can be selected without departing from the scope of the disclosed concept.

Referring to Figure 4, a display unit 4 1 0 includes a power source selection circuit 4 1 2, a secondary power source 4 1 4, a processor 4 1 6, and a memory display 418. Processor 4 1 6 and memory display 418 are similar to respective processor 3 1 6 and memory display 3 18 described above with respect to display unit 3 1 0. Therefore, further description of these components is omitted.

The power source selection circuit 4 1 2 is configured to receive the direct current power VDD and the trip notification. The power source selection circuit 4 1 2 is also electrically connected to the secondary power source 4 1 4 and the memory display 4 1 8. Prior to receiving the trip notification, the power source selection circuit 4 1 2 allows the memory display 4 1 to be powered by the direct current power V _D D- When the power source selection circuit 4 1 2 receives the trip notification, the power source selection circuit 4 1 2 switches the memory display 4 1 8 from the direct current power VDD to the secondary power source 4 1 4.

The secondary power source 4 1 4 includes an energy harvesting component 4 1 5. The energy harvesting component 4 1 5 harvests non-electrical energy such as, for example and w ithout limitation, heat energy or solar energy, and converts it into electrical power which can then be provided to the memory display 4 1 8. The energy harvesting component 4 1 5 can include, for example and without limitation, a photovoltaic cell or a thermoelectric generator. The secondary power source 4 1 4 can also include a capacitor C ₂ , a resistor R ₂ , and a diode Di. Energy harvested by the energy harvesting component 4 1 5 can be stored in the capacitor C ₂ before being provided to the memory display 418 or the harvested energy can be provided to the memory display 41 directly from the energy harvesting component 415.

Referring to Figure 5, a display unit 510 includes a power source selection circuit 512, a secondary power source 514, a processor 516, and a memory display 518. Processor 516 and memory display 518 are similar to respective processor 316 and memory display 318 described above with respect to display unit 310. Therefore, further description of these components is omitted.

The power source selection circuit 512 is configured to receive the direct current power VDD and the trip notification. The power source selection circuit 512 is al o electrically connected to the secondary power source 514 and the memory display 518. Prior to receiving the trip notification, the power source selection circuit 512 allows the memory display 518 to be powered by the direct current power VDD- When the power source selection circuit 512 receives the trip notification, the power source selection circuit 512 switches the memory display 518 from the direct current power VDD to the secondary power source 514.

The secondary power source 514 includes a battery 515. The secondary power source 514 can al o include a capacitor C ₃ , a resistor R ₃ , and a diode D ₂ . Since the memory display 518 uses relatively little power, the memory display 518 draws less power from the battery 515 than a conventional liquid crystal display. In other words, the battery 515 can maintain display of information on the memory display 518 longer than it could on a similarly sized conventional liquid crystal display.

Referring to Figure 6, a display unit 610 includes a processor 616 and a bi -stable display 618. Processor 616 is similar to processor 316 described above with respect to display unit 310. Therefore, further description of the processor 616 is omitted.

The bi -stable display 618 is able to maintain display of information without power. After the processor 616 receives the trip notification and controls the bi -stable display 618 to display the trip information, the direct current power V _D D stops being supplied due to the trip. However, the bi -stable display 618 maintains display of the trip information without the direct current power VDD being supplied to it. It wi ll be appreciated by one having ordinary skill in the art that any one of the display units 3 10,410,5 10,610 disclosed herein can be installed in the circuit interrupter 100, for example, as display unit 1 10 is. It will also be appreciated by one having ordinary skill in the art that any one of the display units

3 10,4 10,5 10,610 can also be configured for use with the circuit interrupter 100', for example, as display unit 1 10' is. An example of the display unit 1 10' configured for use with and coupled to a test port (not shown) of the circuit interrupter 100' is depicted in Figure 7.

While specific embodiments of the disclosed concept have been described in detai l, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.