Field
The disclosed concept pertains generally to electrical switching apparatus and, more particularly, to relays, such as, for example, aircraft relays.
Background Information
A typical normally open relay has a spring (not shown) on its armature mechanism (not shown) that holds the separable main contacts 10 open. In order to initiate movement of the armature mechanism for closure, a relatively large magnetic field is generated to provide sufficient force to overcome the inertia of the armature mechanism and, also, to build up enough flux in the open air gap of its solenoid (not shown) to create the desired force. During closure motion of the armature mechanism, both coil windings 6,8 are energized to produce a sufficient magnetic field. After the main contacts 10 close, the reluctance of the magnetic path in the solenoid is relatively small, and a relatively smaller coil current is needed to sustain the force needed to hold the main contacts 10 together. At this point, an “economizer” or “cut-throat” circuit (not shown) can be employed to de-energize one of the two coil windings 6,8 to conserve power and to minimize heating in the solenoid.
The economizer circuit (not shown) is often implemented via an auxiliary relay contact 12 (E1-E2) that is physically driven by the same solenoid mechanism (not shown) as the main contacts 10. The auxiliary relay contact 12 simultaneously opens as the main contacts 10 close, thereby confirming complete motion of the armature mechanism. The added complexity of the auxiliary contact 12 and the calibration needed for the simultaneous operation makes this configuration relatively difficult and costly to manufacture.
Alternatively, the economizer circuit (not shown) can be implemented by a timing circuit (not shown) which pulses a second coil winding, such as 8, only for a predetermined period of time, proportional to the nominal armature mechanism operating duration, in response to a command for relay closure (i.e., a suitable voltage applied between terminals X1-X2). While this eliminates the need for an auxiliary switch, it does not provide confirmation that the armature mechanism has closed fully and is operating properly.
There is room for improvement in relays.
This need and others are met by embodiments of the disclosed concept in which a relay comprises: a first terminal; a second terminal; a third terminal; a fourth terminal; separable contacts electrically connected between the first and second terminals; an actuator coil comprising a first winding and a second winding, the first winding electrically connected between the third and fourth terminals, the second winding electrically connected between the third and fourth terminals; a processor; an output; a first voltage sensing circuit cooperating with the processor to determine a first voltage between the first and second terminals; and a second voltage sensing circuit cooperating with the processor to determine a second voltage between the third and fourth terminals, wherein the processor is structured to determine that the separable contacts are closed when the first voltage does not exceed a first predetermined value and the second voltage exceeds a second predetermined value and to responsively output a corresponding status to the output.
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:
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 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 statement that two or more parts are “connected” or “coupled” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts. Further, as employed herein, the statement that two or more parts are “attached” shall mean that the parts are joined together directly.
The disclosed concept is described in association with aircraft relays, although the disclosed concept is applicable to a wide range of electrical relays.
Referring to
The example electronic circuit 20 of
Alternatively, AC voltages can be detected if diodes (not shown) are added at the inputs in series with the resistors 98 and 102, and processing of the output signals is provided as was discussed, above, in connection with the circuit 20 of
The voltage sensing circuits 20,50,60,90,110 of
The controller module 142 can be any suitable processor, such as for example and without limitation, an embedded microcontroller circuit, digital logic circuitry and/or discrete analog components. The controller module 142 implements an economizer circuit function by direct control from output 143 of a suitable switch 148 electrically connected in series with the second pull-in solenoid coil winding 150. The switch 148 can be, for example and without limitation, a suitable signal electro-mechanical relay or a suitable semiconductor device, such as a transistor. The controller module 142 sends relay status information 152 by a suitable communication interface 154 to a power distribution unit (PDU), a main controller or a load management controller 156 (e.g., for a vehicle).
A load terminal (A1-A2) differential voltage can be about 50 mV to about 175 mV when the separable contacts are closed in the presence of a suitable load current, while the load terminal A2 can be at about 0 mV when the separable contacts are open.
In Tables 1 and 2:
The disclosed concept replaces a relay auxiliary circuit with voltage sensing electronics. A suitably low voltage between the load terminals (A1-A2) of the relay allows the elimination of a conventional relay auxiliary circuit and provides a status to a PDU, a main controller or a load management controller, such as 156, which needs to know which relays of a power distribution system are on. Further, if the terminal set X1-X2 is high and the terminal set A1-A2 is low, then suitable electronics can be employed to transfer from the pull-in coil to the hold coil. This combines “coil control electronics” or a “cut-throat circuit” function with auxiliary switch functions. This eliminates various mechanical adjustments of the relay, and reduces the cost of the auxiliary switch and the cost of the coil control electronics.
Relays often use the circuit of
Additionally, the disclosed voltage sensing circuits 20,50,60,90,110 and relay systems 140,240,340 can employ a current sensor 400 (shown in phantom line drawing in
Suitable unique current and voltage thresholds can be employed to establish functional health limits for load current and voltage based upon insulation and/or contamination across the separable contacts.
Non-limiting examples of current sensors, such as 400, include Hall effect sensors for DC applications; current transformers for AC load imbalance and ground fault detection; and shunts on, for example, a 270 VDC contactor with corresponding thermal measurement for linear compensation. Current sensors can be placed, for example and without limitation, on terminals or lugs, around conductors, or within contactor buss bars (e.g., Hall effect: shunt).
The disclosed concept can be employed in connection with the following features: (1) determination of contactor “open/close” state and communication of the same to remote systems, such as 156 of
Relay separable contacts, such as 10, usually start with a contact voltage drop (CVD) of about 50 mV to about 60 mV between A1 and A2 when fully closed at rated current. Typical relay specifications allow a change of CVD over life to about 100 mV, 125 mV or 150 mV. Loading on the separable contacts during use is usually about 50% of rating up to about 100% continuous; this concerns how relays or contactors are designed into systems and how they are typically loaded with current as compared to the maximum device rating. A relatively lower contact force corresponds to a relatively higher CVD. The load terminal voltage is essentially zero when the contacts are open. By monitoring the relay timing, when the A1-A2 voltage changes state to the CVD, resulting from the X1-X2 voltage, the voltage for pick-up and drop out and the relay timing can be determined. The ability to compare the A1-A2 voltage versus the X1-X2 voltage and timing allows the relay manufacturer to optimize the coil size, permits determining when to transfer from the pick-up coil to the hold coil, and permits determining the contact open or closed status.
As a result, a mechanical switch and/or a resistor-capacitor circuit are not needed for timing from the X1-X2 input to the state change of the relay separable contacts. The mechanical link from the main separable contacts to the auxiliary switch is one of various error-prone adjustments along with switching from the pull-in coil to the hold (or “release”) coil. For example, the mechanical switch is usually spring actuated, which provides another force that the coil must “overcome”. Because of the lack of “precision” across broad environmental and voltage constraints, the “hold” timing is much broader than it “needs” to be and the coil has to be able to withstand the longer times.
In the disclosed concept, “coil control” electronics or timing circuits are used instead of mechanical adjustments. Mechanical wear would indicate/create a need for a relatively higher pick-up voltage to close the relay. As a result, a threshold can be set for when the pick-up voltage change is outside an acceptable range or trending to show wear.
Similarly, the drop-out voltage can be monitored. If more friction occurs, then this can be observed since the relay will hold closed at a relatively lower voltage. Also, the relay timing will change. As a result, a threshold can be set for when the drop-out voltage change is outside an acceptable range or trending to show wear.
While the example terminal voltage sensing circuits of
In addition to determining wear by monitoring changes in operational voltages over a relay's life, changes in timing of the logic signals may also be used as indication of mechanism wear. For example, if the time period between detection of voltage application to the coil control terminals X1,X2 and the detection of appropriate voltages at relay terminals A1,A2 indicating contact closure increases, then this may be indicative of jamming or drag in the relay mechanism. A suitable predetermined maximum duration for this period may be determined for allowable relay performance, beyond which the relay may need to be inspected, serviced or replaced.
A thermistor or other suitable temperature sensor can be added to account for temperature effects. For example, the resistance of copper changes with temperature. The thermistor measures the temperature of the copper as an input to provide a linear signal when measuring current for over-current protection.
While specific embodiments of the disclosed concept have been described in detail, 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.
This application claims the benefit of U.S. Patent Application Ser. No. 61/609,532, filed Mar. 12, 2012, which is incorporated by reference herein.
Filing Document | Filing Date | Country | Kind |
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PCT/US2013/020770 | 1/9/2013 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2013/137971 | 9/19/2013 | WO | A |
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Number | Date | Country | |
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61609532 | Mar 2012 | US |