Method and apparatus for handling contactor / relay contact bounce under transient conditions - Patents.com

Abstract

Contact bouncing in the contactor is detected by measuring contact voltage fluctuations caused by bouncing of the powered contacts controlled by the contactor. When a fluctuation is detected, the circuit temporarily re-energizes the contactor's retraction coil to reset the higher magnetic field needed to attract and hold the powered contacts in the proper position to remove the bounce. Because of the high power needed for the retraction coil, the time it is activated is limited to avoid thermal damage to the coil or other electronic components. Activating the retraction coil properly positions the powered contacts, and energizing the lower magnetic field holding coil maintains the position of the powered contacts. The time the retraction coil is activated may be dynamic and may correspond to each disturbance as it occurs, it may be a set time determined by a timer, or it may be controlled by a pulse width modulation scheme.

Description

Detailed Description of the Invention

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims the benefit under 35 U.S.C. §119(e) of Provisional Application No. 63 / 219,684, filed July 8, 2021, the entire contents of which are incorporated herein by reference as if fully set forth herein. [Field of the Invention] The present invention relates generally to contactors, and more particularly to addressing the effects of disturbances that cause contact bouncing in a contactor. [Background to disclosure] A contactor is essentially a switch that is actuated by energizing an electromagnet, which then attracts a conductive bar across two contacts, bridging them so that power can flow across them to a load. In some applications, contactors are used to selectively supply power to specific loads. Firing a gun on a military aircraft is one example that can cause high transient vibrations that can cause the contacts of an on-board contactor to bounce or chatter during a vibration event. This can cause damaging arcing in the contacts and power transients to the load the contactor is powering. Although contact bounce can be partially mitigated by special vibration-damping mounts for the contactor, such mitigation is often insufficient and / or unreliable.

[0002] As illustrated in FIG. 1, an exemplary contactor 100 for high currents includes two magnetic coils, often arranged in series, to magnetically close the contacts and keep them closed while powering the load. The first coil, called the pull-in coil 102, generates a high magnetic field to quickly close the contacts. The second coil, called the hold coil 104, generates a lower magnetic field to hold or maintain the contacts closed once already closed by the pull-in coil 102. The hold coil 104 is shorted by closing a switch 108. Typically, when it is desired to power a particular load, a signal is applied to close the switch 108 for a period of time. As a result, the pull-in coil 102 sets up the higher magnetic field required to operate and close the contacts used to power the load. The two coil arrangement is required to minimize the power consumed by the electromagnet because the high initial magnetic field for the pull-in coil 102 requires a large amount of power to generate and is not needed to keep the contacts in the proper position after the contactor is closed; only the holding coil 104 needs to be energized.

[0003] Once the power delivery contacts are closed, power is delivered to the load and the switch 108 is opened, allowing the holding coil 104 to set up a lower magnetic field sufficient to energize the holding coil 104 (but not the retraction coil 102) to keep the power delivery contacts closed. In contrast to the retraction coil 102, the holding coil 104 requires a much smaller magnetic field to hold or maintain the closed contacts closed. Under high vibration conditions or other disturbances, the power delivery contacts may bounce or chatter or otherwise move, resulting in arcs, power transients, or other undesirable conditions. During this time, the contactor is only operating with the lower magnetic field of the holding coil 104, so the contactor may not be able to fully actuate the power delivery contacts, which would require the higher magnetic field of the retraction coil 102. This results in an interruption of the power delivery. It is also undesirable to always fully utilize the retraction coil 102. This is because not only is an excessive amount of power being consumed, but it also results in the generation of high levels of heat energy which can in turn cause further undesirable failures or conditions. [Summary of the Invention] The present invention addresses these and other known deficiencies in conventional power delivery contactor devices. In an embodiment, the present invention detects contact bouncing by measuring the fluctuations in contact voltage caused by the bouncing contacts. When these fluctuations are detected, a circuit temporarily re-energizes the retraction coil to re-establish the higher magnetic field needed to more firmly re-attach the contacts, eliminating the bouncing. Due to the high power required for the retraction coil, the amount of time the retraction coil is activated is limited to avoid thermal damage to the coil or other electronic components. [Brief description of the drawings]

[0004] For a more complete understanding of the present invention, its objects and advantages, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: [Figure 1] FIG. 1 is a schematic diagram of a prior art contactor. [Diagram 2] FIG. 2 is a schematic diagram of an improved contactor control according to a first embodiment of the present invention. [Diagram 3] FIG. 5 is a schematic diagram of an improved contactor control according to a second embodiment of the present invention. [Figure 4] FIG. 5 is a schematic diagram of an improved contactor control according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] Detailed Description of the Preferred Embodiments of the Invention Disclosed are several embodiments of the present invention that may be used to selectively control the operation of a pull-in coil in a contactor device to minimize heat generated when powering a load under conditions where disturbances may affect the power supply and / or operation of the contactor.

[0006] Reference is now made to Figure 2, which illustrates a schematic diagram of a first embodiment of the present invention. As shown in Figure 2, a contactor 200 includes a pull coil 202 and a hold coil 204, as described above in connection with Figure 1. However, in this embodiment, a voltage sense 210, such as a differential amplifier, may be used to selectively operate a switch 208, which in turn selectively shorts or opens the hold coil 204. The inputs to the voltage sense 210 are a high voltage input 212 and a high voltage output 214. The high voltage input 212 represents the vehicle or aircraft power bus, such as a "hot wire," as is well known in electrical systems, while the high voltage output 214 represents the voltage at the load, or what is sometimes referred to as the load connection. Under normal operating conditions when power is being supplied to the load, the high voltage input 212 should essentially be the same as the high voltage output 214, and there will be no (or negligible) output from the voltage sense 210. As a result, the switch 208 is otherwise unchanged, the holding coil 204 is energized, and the contacts controlled by the holding coil 204 are closed to supply power to the load.

[0007] If a disturbance occurs while power is being delivered to the load, this will typically cause a difference between the voltages observed at the high voltage input 212 and the high voltage output 214. This voltage difference is detected by the voltage sense 210, and the output of the voltage sense 210 is enabled to actuate the switch 208 to a closed position, shorting the holding coil 204 and allowing the pull-in coil 202 to increase the magnetic field, thereby returning the power delivery contacts to their predetermined position to reliably deliver power to the selected load. As soon as power is properly delivered to the selected load, the high voltage output 214 should then return to being essentially the same as the high voltage input 212. As soon as this voltage balance is achieved, the differential input to the voltage sense 210 becomes negligible. As a result, the output of the voltage sense 210 will be disabled, not actuating the switch 208. As soon as the switch 208 is no longer actuated, the holding coil 204 is no longer shorted and will operate to set the magnetic field at a much lower level than was required for the pull-in coil 202.

[0008] Unless further disturbances or vibrations are encountered, the power supply contactor will continue to supply power to the load under normal operation while only the holding coil 204 is energized via a lower magnetic field than the much higher magnetic field required for the pull-in coil 202. As soon as another disturbance or vibration is detected, which would normally appear as a voltage difference between the high voltage input 212 and the high voltage output 214, the voltage sense 210 will enable its output and the process will continue as described above by closing the switch 208 to re-energize the pull-in coil 202. In this way, any disturbance or vibration will be sensed, for example by a voltage difference, and the contactor will be reset to energize the pull-in coil 202.

[0009] FIG. 3 presents an alternative embodiment, which operates much the same as the embodiment of FIG. 2. Like elements in FIG. 3 are referred to with similar numbers as those used in FIG. 2. With specific reference to FIG. 3, the output of the voltage sense 310 is instead used to activate a one-shot timer 316, which activates the switch 308, instead of directly activating the switch 308 as is similarly done in the embodiment of FIG. 2. In the embodiment of FIG. 3, once a disturbance or vibration is detected, for example by the voltage sense 310, the output of the voltage sense 310 is used to activate a one-shot timer, which may be programmed to provide a valid output for a preselected amount of time. This valid output of the one-shot timer 316 is used to close the switch 308, which shorts the holding coil 304 and the retraction coil 302 sets a much higher magnetic field so that the power delivery contacts return to or remain in their proper positions. In this way, in contrast to the embodiment of FIG. 2, a disturbance or vibration condition may be used to re-energize the retraction coil 302 for a particular time, which essentially operates in real time or near real time to address each disturbance or vibration event as it occurs. The embodiment of FIG. 3 may be advantageous in environments where it is known that continuous disturbances may occur, or that multiple disturbances may occur in a relatively short period of time. Instead of having to repeatedly operate the power supply contacts, the power supply contacts are operated once, based on the time set in the one-shot timer 316. If high vibration persists after this time limit is reached and the contacts resume bouncing, the retraction coil 302 may be re-energized for another time interval.

[0010]

[0023] Referring now to Figure 4, there is illustrated yet another alternative embodiment similar to the embodiment described above, but in this alternative embodiment, the pull-in coil 402 is supplied with a reduced average current that results in a much higher magnetic field than that generated by the hold coil 404 alone, but less than the current that would result from fully activating the pull-in coil 402. Figure 4 presents an alternative embodiment that operates much like the embodiment of Figure 2. Similar elements in Figure 4 are referred to using numbers similar to those used in Figure 2. With specific reference to Figure 4, the output of the voltage sense 410 is instead used to activate a logic circuit 416, which in turn provides pulse width modulated (PWM) outputs, such as signal sequences 418 and 420. A PWM signal such as 418 or 420 is then used to actuate switch 408 to short out holding coil 404 when needed to cause the retraction coil 402 to establish a high magnetic field to return or maintain the voltage supply contacts in their proper positions. The PWM approach of FIG. 4 still utilizes much less current and generates much less heat energy than if the retraction coil 402 were energized all the time, because the retraction coil 402 is only energized for a portion of the time. The ON time of this period, otherwise referred to as the duty cycle, may be set based on the particular needs or desired operation of the system.

[0011] As discussed above in connection with various embodiments, the amount of current required to hold the power delivery contacts closed may be predetermined based on the aircraft or vehicle design, and a software algorithm or digital logic may be created to begin reducing the current to the retraction coil after a certain amount of time, reducing the current to zero if the vibrations stop, or increasing the current again if the contact chatter resumes.

[0012] It will be understood that the embodiments disclosed herein extend to all alternatives and combinations. It will be further understood by those skilled in the art that the present invention is applicable to a wide range of uses and applications. Numerous embodiments and variations of the invention other than those described herein, as well as numerous adaptations, modifications, and equivalent arrangements, will be apparent from, or reasonably suggested by, the present invention and its description without departing from the spirit or scope of the invention.

[0013] Thus, while the invention has been described in detail herein in connection with exemplary embodiments, it is to be understood that the disclosure is merely illustrative and exemplary of the invention, and is provided for the purpose of providing a fully enabling disclosure. Moreover, the foregoing description is not intended to be construed as limiting the invention or to exclude any adaptations, modifications, or equivalents thereof.

Claims

1. A circuit device capable of reducing contact bounce in a contactor due to a transient state, A contactor having a first magnetic coil electrically connected to a second magnetic coil, wherein one or both of the first magnetic coil and the second magnetic coil are configured to close contacts when power is supplied to a load, and the first magnetic coil generates a higher magnetic field than the second magnetic coil; A switch configured to selectively electrically short-circuit the second magnetic coil so that the first magnetic coil can generate the higher magnetic field; A voltage sensor configured to detect voltage fluctuations caused by the transient state, the voltage sensor having an output used to selectively activate the switch to energize the first magnetic coil to generate the higher magnetic field; A circuit device comprising the above.

2. The circuit device according to claim 1, The first magnetic coil includes a pull-in coil, The second magnetic coil includes a holding coil, The circuit device in which the pull-in coil and the holding coil are connected in series.

3. The circuit device according to claim 2, The voltage sensor is a differential amplifier having a first input in conduction with a power bus and a second input in conduction with a load voltage connection, and the output of the differential amplifier is configured to indicate a voltage difference between the power bus and the load voltage connection. The circuit device includes a differential amplifier.

4. The circuit device according to claim 3, The pull-in coil is temporarily energized when a disturbance is detected and de-energized when the disturbance is no longer detected.

5. A circuit device capable of reducing contact bounce in a contactor due to a transient state, Having a first magnetic coil electrically connected to a second magnetic coil, wherein one or both of the first magnetic coil and the second magnetic coil are configured to close contacts when power is supplied to a load, and the first magnetic coil generates a higher magnetic field than the second magnetic coil; A switch configured to selectively electrically short-circuit the second magnetic coil so that the first magnetic coil can generate the higher magnetic field; A voltage sensor configured to detect a voltage fluctuation caused by the transition state, having an output used to selectively operate a timer, and the timer magnetizes the first magnetic coil by operating the switch for a selectable time to generate the higher magnetic field, the voltage sensor, A circuit device comprising the same.

6. The circuit device according to claim 5, The first magnetic coil includes a pull-in coil, The second magnetic coil includes a holding coil, The circuit device in which the pull-in coil and the holding coil are connected in series.

7. The circuit device according to claim 6, The voltage sensor is a differential amplifier having a first input in conduction with a power bus and a second input in conduction with a load voltage connection portion, and an output of the differential amplifier is configured to indicate a voltage difference between the power bus and the load voltage connection portion, the circuit device comprising the differential amplifier.

8. The circuit device according to claim 7, The circuit device in which the pull-in coil is temporarily magnetized when a disturbance is detected and demagnetized after the selectable time has elapsed.

9. A circuit device capable of reducing contact bounce in a contactor due to a transition state, Having a first magnetic coil electrically connected to a second magnetic coil, one or both of the first magnetic coil and the second magnetic coil are configured to close a contact when power is supplied to a load, and the first magnetic coil generates a higher magnetic field than the second magnetic coil, a contactor, A switch configured to selectively electrically short-circuit the second magnetic coil so that the first magnetic coil can generate the higher magnetic field, A voltage sensor configured to detect a voltage fluctuation caused by the transition state, the voltage sensor having an output used to operate a pulse width modulator having a selectable duty cycle, and an output of the pulse width modulator magnetizes the first magnetic coil by selectively operating the switch on and off according to the selectable duty cycle to generate the higher magnetic field, the voltage sensor, A circuit device comprising the same.

10. The circuit device according to claim 9, The first magnetic coil includes a pull-in coil, The second magnetic coil includes a holding coil, A circuit device in which the pull-in coil and the holding coil are connected in series.

11. The circuit device according to claim 10, wherein the voltage sensor is a differential amplifier having a first input in conduction with a power bus and a second input in conduction with a load voltage connection portion, and an output of the differential amplifier is configured to indicate a voltage difference between the power bus and the load voltage connection portion, and the circuit device includes the differential amplifier.

12. The circuit device according to claim 11, wherein the pull-in coil is temporarily excited when a disturbance is detected and demagnetized according to the selectable duty cycle of the pulse width modulator.

13. A method for reducing contact bounce in a contactor caused by a transient state, including the step of using a contactor having a first magnetic coil electrically connected to a second magnetic coil, wherein one or both of the first magnetic coil and the second magnetic coil are configured to close contacts when power is supplied to a load, and the first magnetic coil generates a higher magnetic field than the second magnetic coil; the step of selectively operating a switch configured to selectively electrically short-circuit the second magnetic coil so that the first magnetic coil can generate the higher magnetic field; the step of using a voltage sensor configured to detect voltage fluctuations caused by the transient state, wherein the voltage sensor has an output used to excite the first magnetic coil to generate the higher magnetic field by selectively operating the switch. A method comprising the above steps.

14. The method according to claim 13, wherein the first magnetic coil includes a pull-in coil, the second magnetic coil includes a holding coil, and the pull-in coil and the holding coil are connected in series.

15. The method according to claim 14, wherein the voltage sensor is a differential amplifier having a first input in conduction with a power bus and a second input in conduction with a load voltage connection portion, and an output of the differential amplifier is configured to indicate a voltage difference between the power bus and the load voltage connection portion.

16. The method according to claim 15, A method wherein the pull-in coil is temporarily excited when a disturbance is detected and demagnetized when the disturbance is no longer detected.

17. A method for reducing contact bounce in a contactor due to a transient state, comprising the step of using a contactor having a first magnetic coil electrically connected to a second magnetic coil, wherein one or both of the first magnetic coil and the second magnetic coil are configured to close the contacts when power is supplied to the load, and the first magnetic coil generates a higher magnetic field than the second magnetic coil; the step of selectively operating a switch configured to selectively electrically short-circuit the second magnetic coil so that the first magnetic coil can generate the higher magnetic field; the step of using a voltage sensor configured to detect a voltage fluctuation caused by the transient state, the voltage sensor having an output used to selectively operate a timer, and the timer exciting the first magnetic coil by selectively operating the switch for a selectable time to generate the higher magnetic field; A method comprising the above.

18. The method according to claim 17, wherein the first magnetic coil includes a pull-in coil, the second magnetic coil includes a holding coil, and the pull-in coil and the holding coil are connected in series.

19. The method according to claim 18, wherein the voltage sensor is a differential amplifier having a first input in conduction with a power bus and a second input in conduction with a load voltage connection, and the output of the differential amplifier is configured to indicate a voltage difference between the power bus and the load voltage connection.

20. The method according to claim 19, wherein the pull-in coil is temporarily excited when a disturbance is detected and demagnetized after the selectable time has elapsed.

21. A method for reducing contact bounce in a contactor due to a transient state, comprising the step of using a contactor having a first magnetic coil electrically connected to a second magnetic coil, wherein one or both of the first magnetic coil and the second magnetic coil are configured to close the contacts when power is supplied to the load, and the first magnetic coil generates a higher magnetic field than the second magnetic coil; A step of selectively operating a switch configured to selectively and electrically short-circuit the second magnetic coil so that the first magnetic coil can generate the higher magnetic field; A step of using a voltage sensor configured to detect voltage fluctuations caused by the transient state, the voltage sensor having an output used to operate a pulse width modulator having a selectable duty cycle, and the output of the pulse width modulator selectively operating the switch on and off according to the selectable duty cycle to excite the first magnetic coil to generate the higher magnetic field; A method comprising. **Claim 22** The method according to claim 21, The first magnetic coil includes a pull-in coil, The second magnetic coil includes a holding coil, The method wherein the pull-in coil and the holding coil are connected in series. **Claim 23** The method according to claim 22, The voltage sensor is a differential amplifier having a first input in conduction with a power bus and a second input in conduction with a load voltage connection, and the output of the differential amplifier is configured to indicate a voltage difference between the power bus and the load voltage connection, the method comprising a differential amplifier. **Claim 24** The method according to claim 23, The method wherein the pull-in coil is temporarily excited when a disturbance is detected and demagnetized according to the selectable duty cycle of the pulse width modulator.

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