US 3835333 A
A system for providing continuous operation of electrical appliances, lights, etc. comprising a primary load circuit and a secondary load circuit. Each of the load circuits having a source of power and a load. Monitor means is arranged between the primary and secondary load circuits which is responsive to the passage of current in the primary circuit to maintain the secondary circuit inoperative, and responsive to the cessation of current in the primary circuit to render said secondary circuit operative. Preferably the monitor means comprises a transformer and a solenoid relay.
Description (OCR text may contain errors)
United States Patent [1 1  3,835,333 Balan Sept. 10, 1974 4] REDUNDANT ELECTRICAL SYSTEM Primary Examiner-Herman J. l-lohauser  Inventor: Markandan Hari Balm, 3363 Attorney, Agent, or Firm-Wi1liam Anthony Drucker Sedgwick Ave., Bronx, NY. 10463  Filed: Mar. 19, 1973  ABSTRACT  Appl. No.: 342,847 A system for providing continuous operation of electrical appliances, lights, etc. comprising a primary load circuit and a secondary load circuit. Each of the load 2% i 307/ circuits having a source of power and a load. Monitor d 18 29 means is arranged between the primary and secondary 1 Re 0 earc load circuits which is responsive to the passage of cur- 56 R f Ct d rent in the primary circuit to maintain the secondary 1 e erences e circuit inoperative, and responsive to the cessation of UNITED STATES PATENTS current in the primary circuit to render said secondary 1,753,101 4/1930 Whittingham 307/66 circuit operative. Preferably the monitor means com- 1,882,472 10/ 1932 Beetein' 307/66 prises a transformer and a solenoid relay. 2,992,363 7/1961 Granquist 307/66 UX 4 Claims, 1 Drawing Figure c I q BACKGROUND OF INVENTIONv The present invention relates to redundant electrical load systems and in particular to electrical systems wherein a supplemental load is automatically activated on the expiry or breakdown of the'primary load.
There are many occasions when an electrical load constitutes the sole safety measure and the sole means for performing the desired work. For example, such areas as stairwells, highways, subway areas, are lit bya single system of lights, which when the bulbs burn out leave the area in total darkness. These areas are sometimes so inaccessible that the time required to locate and determine the existence of burned out lights is frequently so long that an accident, crime or other misfortune can occur during that period. There are also other instances wherein a single electric load system is used to perform the necessary work and which constitutes the sole source of safety with regardto the constant uninterrupted use. Such instances may include the operation of refrigeration systems, clock systems and the like wherein when the compressor, clock or other load device breaks down minor catastrophe may result. The breakdown of power to an electrical supply system is easily determined since power is generally supplied from a common source by a common utility whose interest it is to see that the power source is continuous. However, the breakdown at the load, that is the bulbs, the motor, the compressor, for example, is generally the function of the user himself. In large installations such as subways, apartment houses, cold storage and refrigeration units it is uneconomical to provide a constant manpower'to supervise and control the continuous operation of the load. Presently there is no way of knowing when the load itself is going: to burn out or break down and the supervisory manpowermay take several hours and sometimes days before the breakdown is located.
It is an object of the present invention to provide an electrical system wherein redundant or. supplemental systems are provided which are automatically activated upon the breakdown of the load of the primary or first system.
It is another object of the present. invention to provide a redundant electrical system which may be easily incorporated in present primary load systems without the need for sophisticated and costly equipment.
It is a further object of the present invention to provide a redundant electrical systemwhich may be applied to any electrical load be it the simple lighting system and/or the use of any one of the many electrical appliances currently available.
The prime object of the present invention is to provide means for the continuous, uninterrupted and reliable operation of an electrical load system. The present invention, by providing means for switching to standby equipment, when the primary equipment fails, introduces a revolutionary concept of safety, continuous operation, and economy to electrical systems and particularly to those sensitive systems such as lighting, refrigeration and the like.
The above objects and advantages, together with numerous others, will be found in the following'disclosure of the present invention.
SUMMARY OF INVENTION According to the present invention a redundant lighting system is provided comprising a primary load circuit having at least a source of power and a load such asthe aforementioned bulb or motor, to this primary system are added at least one secondary circuit also having a source of power and a load corresponding to that of the primary system. A monitoring unit is arranged between the first and secondary system and between each of the successive secondary systems in line. The monitoring device contains operable means responsive to the passage of current in the primary circuit, which means maintain the secondary circuit inoperative during the passage of such current but on the failure of such current in the primary circuit causes the secondary circuit to operate.
Preferably, the monitoring devices comprise simply a transformer and a solenoid relay having at least one pair of normally closed contacts. The primary winding of the transformer is arranged in series with a power source and load of primary circuit while the output or secondary winding of the transformer is arranged in series with solenoid to control the operation of the relay. The contacts of the relay are arranged in series with the source of power and of the load of the secondary or supplemental circuit. Thus, so long as power is maintained in the primary circuit a current is induced in the solenoid which maintains the relay contacts in open position against its normal bias, thus rendering the supplemental circuit inoperative. However, as soon as the current ceases to flow in the primary load circuit the no current is induced through the solenoid of the relay and thus the contacts close activating the supplemental second circuit so that its power source will operate its load device. Upon activation of the supplemental circuit its circuit becomes in effect a primary circuit producing the light or operating the electrical appliance and in turn becoming the primary circuit for any further supplemental circuit connected in cascading form therewith.
It is further advantageous to provide indicator means arranged in the circuit parallel to the load of the supplemental circuit which indicator may be placed at a remote position from the load of the supplemental circuit and which instantaneously upon the activation of the supplemental circuit also provides an indicating signal that this supplemental circuit has been activated. Thus, the indicator signal would advise not only the activation of the supplemental circuit but also of the breakdown of the primary circuit.
Full details of the present invention are given in the following description of the preferred embodiments and are shown in the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING In the drawing:
The FIGURE is a circuit diagram of a redundant lighting system having a primary circuit and at least two supplemental circuits cascading therefrom.
DESCRIPTION OF INVENTION As seen in the drawing, the system of the present invention provides a primary load or work circuit generally illustrated by the number 10, and two sequential but independently functioning secondary work circuits 20 and 30. The circuits are shown for illustration only,
spectively. However, it is to be clearly understood that the light may be replaced with any other electrical load such as a motor, compressor and electrical appliance or the like Each of the primary and secondary circuits is powered by a source of power 14 and 24 and respectively which-may be a conventional generator, house circuit delivering utility supply current, or any other source or combination. If desired and where practical the sources may be common for all of the secondary circuits as well as for the primary circuit.
The circuits are successively connected by monitoring devices which comprise a coupling transformer 16 and 26 and, a normally closed solenoid operated relay 18. Theprimary winding of the coupling transformer is as operating and controlling a light 12, 22, and-32 reconnected in series directly between the power source and the load of each of the circuits while the secondary or output winding of the coupling transformer is connected in series with the winding of the solenoid of the relay 18 Each relay has a primary contact A which is provided in series with the power source and the load of the sequentially arranged secondary circuit.
Each relay is a conventional solenoid operated relay having a spring loaded bias which maintains the contacts in normally closed position unless the solenoid is activated whereupon the contacts are maintained open for so long as the activation of the solenoid continues. In the embodiment shown each of the relays has a secondary contact B to which a pilot light is arranged in parallel with the load of the respective secondary circuit. The pilot light P may of course be placed at a remote position from the load as for example at a common control board which may be constantly and easily supervised. I While one primary and only one secondary circuit are shown, as many secondary circuits as may be desired can be strung together or cascaded. The duplication of the circuits including the couplingtransformers and the relay 18 will be obvious from the drawing and from the foregoing description.
In operation the primary circuit ,10 is made to function in the normal and conventional manner, that is, as if the load were unconnected to any secondary circuitry. For example, it can be assumed that the primary circuit is arranged to light a subway platform or passage and that the light source 12 must be constantly supplied with power and must be constantly allowed to remain lit. Simultaneously with the lighting of the light source 12 in the primary circuit an EMF is produced through the coupling transformer 16 which induces a current through its output coil which is passed on to the relay 18. The solenoid of the relay 18 is activated and maintains the contacts A and B (if used), open. The contacts remain open So long as the primary circuit is completed and the light 12 remains lit. The open contacts of the relay l8 maintain the secondary circtui 20 inoperative which will remain unfunctional so long as current passes through the primary circuit. Should the bulb 12 however break down, that is burn out, the primary circuit current is interrupted and instantaneously the induced current (EMF) in the output coil of the coupling transformer ceases and the solenoid of the relay 18 is deactivated releasingthe contacts. The contact A closes and instantaneously the circuit of the secondary circuitsystem is in full connection and power is delivered to the bulb 22 of the secondary circuit and the pilot light P is illuminated.
From the foregoing, it will be obvious that an instantaneous switching from the primary to the secondary circuits takes place as soon as the load fails or breaks down. This load is not dependent upon anything other than the continuous flow of current to the load. Furthermore, if a pilot is used the pilot light is simultaneously lit as soon as the load of the secondary circuit is placed into opposition. This provides an immediate and possibly remote indication that the primary load has broken down and that the secondary load is in use. This is particularly advantageous when the load for example is not readily visible or accessible to immediate supervision. It is to be noted that as soon as the secondary circuit comes into operation, the relay of the third circuit is actuated, opening the circuit of the third load and insuring therefor that only one load at one time is in operation. A further advantage of the present invention is-the fact that the redundant lighting system is reversable, that is, should the first or primary load for some reason be reactivated as by replacement of the bulb, an automatic deactivation of the secondary systems will take place. The replacement of the bulb in the primary system immediately places current through the coupling transformer 16 which reactivates the solenoid of the relay 18 opening the contacts A thus breaking the connection between the power and the load in the secondary source 20.
The parameters of any particular circuit and redundant system arrangement will depend of course on the load, source and conduits employed. It is most particularly dependent upon the value of the load impedance, which is the most critical factor. Since the load impedance is generally much higher than any other factor in this arrangement the introduction of the coupling transformer and relay presents only a minor change in the parameter of currently existing circuits. The monitor components, that is the coupling transformer and the relay will be chosen to introduce as little variance in the circuit as possible. This is so because the transformer output need produce an EMF sufficient only to activate the coil of the solenoid. No load need be carried through the output of the transformer or through the solenoid relay other than to overcome the bias of the spring of the relay. Transformers and relays of low impedance are quite conventional and commonly available. Transformers having a greater number of turns in the secondary winding than in the primary winding will insure a suitably low impedance while producing a sufficiently high EMF in the relay. A ratio of at least l0 to l is suitable.
From the foregoing, it will be seen that a successful redundant load system is provided wherein under normal operating conditions only the primary circuit is functioning and where an instantaneous switching over into the secondary systems is effected without any delay or the need to activate any supplemental power source or switching mechanism. In accordance with the present invention cotinuous operation of the load, that is, lighting or working of an electrical appliance is insured without major breakdown or catastrophe.
,Various changes and modifications may be made without departing from the scope of the present invention. The disclosure of the present invention should be taken .as illustrative only and not as limiting the scope of the invention.
What is claimed is:
1. A redundant electrical system for alternating current comprising a primary load circuit and a secondary load circuit, each of said circuits having a source of power and a load, and transformer and relay monitor means arranged between the primary and secondary load circuits, said monitor means being responsive to the passage of current in the primary circuit to maintain the secondary circuit inoperative, and responsive to the cessation of current in the primary circuit to render said secondary circuit operative, said monitoring means comprising a transformer and a solenoid relay; the primary winding of said transformer being connected in series with the power source and load of said primary circuit and the secondary winding of said transformer being in series with the solenoid of said relay, said relay having contacts in series with the power source and load of the secondary circuit.
2. The system according to claim 1 wherein said relay is spring loaded in normally closed position.
3. The system according to claim 1 wherein said monitoring means includes an indicator of the condition thereof.
4. The system according to claim 1 including a second contact in said relay and a pilot indicator connected thereto in parallel to the load of said second circuit, said indicator being operable on flow of current in said second circuit.