US3441829A

US3441829A - Emergency stand-by electric service apparatus

Info

Publication number: US3441829A
Application number: US717471A
Authority: US
Inventors: Frederick G Perkins; Carl Edward Minick
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-03-25
Filing date: 1968-03-25
Publication date: 1969-04-29
Anticipated expiration: 1986-04-29

Description

April 29, 1969 F. G. PErKlNs T AL 7 3,441,829

EMERGENCY STANDBY ELECTRIC SERVICE APPARATUS Original Filed Dec. 16, 1965 Sheet of 2 \f ::Z;g1

J0 ooooopnnn 1 .2w I llllllll INVENTOR Rafi/4K6 flaw r5 6M1 sad/4001mm r15 9& BY yw j ATTORNEY EMERGENCY STAND-BY ELECTRIC SERVICE APPARATUS Original Filed Dec. 16, 1965 Sheet 5 of 2 gii'g INVENTOR BY M ATTORNEY United States Patent US. Cl. 320-40 Claims ABSTRACT OF THE DISCLOSURE A battery charging arrangement has a transformer-rectifier for producing direct current connected by two conductors to a battery for charging it; in one of the conductors is an SRC and a control circuit for the SRC which includes a valve responsive to the voltage of the battery to render the SRC conductive when the battery voltage drops so as to recharge the battery, and a Zener diode in parallel with the control valve of the circuit to regulate the voltage at which the second valve becomes operative; a light is so connected as to connect it to the battery if the alternating current fails.

This application is a continuation of application No. 584,002 filed Oct. 3, 1966 now abandoned and application No. 330,825 filed Dec. 16, 1963 now abandoned.

This invention relates to emergency electrical systems, and more particularly to emergency lighting and alarm systems.

An object of the invention is to provide a novel and improved emergency lighting and alarm system which may be readily installed in buildings and other structures as an adjunct to the normal lighting service to provide emergency facilities upon failure of said service.

Another object of the invention is to provide an improved emergency or stand-by apparatus as above set forth, which is extremely reliable and foolproof in its operation.

A further object of the invention is to provide an improved stand-by lighting and alarm apparatus in accordance with the above, which is relatively simple in construction, inexpensive to fabricate and economical to maintain.

A still further object of the invention is to provide an improved stand-by apparatus in accordance with the foregoing, which is trouble-free in operation and requires little or no servicing, or replacement of parts throughout an extended period of use.

Still another object of the invention is to provide an improved stand-by emergency lighting system which will set off an alarm in the event of failure of the power source thereof, and which will also provide an indication of fuse failure in the stand-by circuits.

A feature of the invention resides in the provision of a novel auxiliary power supply and control unit, which may be placed in a convenient location in the building, as determined by the available space.

A still further object of the present invention is to provide an improved auxiliary lighting or stand-by apparatus adapted to supply a multiplicity of stand-by circuits, wherein automatic energization of any one or several of said circuits is provided for automatically in response to failure of one or several of the regular service circuits.

A further feature of the invention is to provide an emergency lighting and alarm system which has no moving parts whatsoever, in as much as all operations are performed in conjunction with various solid state semiconductor devices. This is accomplished in both the battery charging and in the automatic connection of emergency electrical load.

A particular feature of the invention is the use of a Schmitt trigger circuit in conjunction with a Zener diode regulator to establish a fixed reference voltage at the emitter of the control transistor of the trigger circuit so that in battery charging, a precise switching voltage to a different charging rate can be achieved, and with a resulting lower voltage the hysteresis of the trigger circuit prevents the oscillating switching of the transistors of the trigger circuit.

Further objects and advantages of the invention will appear more fully from the following description, particularly when take in conjunction with the accompanying drawings, which form a part thereof.

In the drawings:

FIG. 1 shows diagrammatically a circuit embodying the invention;

FIG. 2 shows part of a modified circuit; and

FIG. 3 shows a part of a further modification.

Referring to FIG. 1, the primary purpose of the invention as herein disclosed is to provide for the lighting of emergency lights 2 in the event of failure of the current in a conventional AC system 4 by means of a battery 6, and to provide for recharging of this battery automatically whenever its charge drops below a predetermined value.

The circuit as shown has a pilot light 8 connected to the main circuit, as well as the primary winding of a transformer 10. A midpoint of this secondary winding is connected to line 12, while the ends of the secondary winding are connected by rectifiers D to line 14. Line 12 is connected to the positive terminal of the battery while line 114 is connected to the negative terminal through silicon-controlled rectifier 16, and, in parallel with it, resistance R and rectifier D these being joined at a common point 11.

Resistances R and R are connected in series to line 12 and to the collector of transistor Q The emitter of this transistor is connected through switch S and resistance R; to point b. The base of transistor Q is connected to a midpoint of resistance R connected between

lines

12 and 14. Zener diode Z is connected in a line running from a point between resistances R and R to line 14.

The resistance R, is connected at a point between resistance R and the collector of transistor Q to the base of transistor Q The collector of transistor Q is connected through a resistance R; to line 12, and its emitter is connected through resistance R to resistance R The base of transistor Q, is connected between resistance R and the collector of transistor Q Its emitter is connected through resistance R to the line 12, and its collector through the resistance R to the SRC gate 16.

The base of transistor Q, is connected to a point be tween resistance R and the emitter of transistor Q and its emitter is connected to the line 12. Its collector is connected through pilot light P to line 14.

The lamps 2 are connected at the side of the negative pole of battery b and at the other side of the collectors of transistors Q and Q The emitter of transistor Q is connected to the positive side of battery 6 and its base is connected to the emitter of transistor Q The base of transistor Q is connected to the collector of transistor Q The emitter of this transistor is connected to line 12 while its base is connected to line 12 through resistance R and through resistance R of rectifier D D connected across the secondary of transformer 10.

During normal operation, as will be explained hereinafter, the battery 6 is kept at full charge. During this operation, the main line current at 4 is continuous, so that transformer 10 is energized. Through rectifier D D transistor Q is biased across resistance R and is conductive from line 12 to line 14. Q and Q are not conducting because Q is effectively shorted by Q and R The lights are therefore not lighted. A condensor C is provided to filter the Q bias.

If the power fails, transformer 10 is no longer energized and Q is no longer conductive. Q and Q are then biased through their emitter-bases through R causing them to conduct and thus energize the emergency lights 2. To obtain an on-off bias to Q a negative source is obtained directly from the alternatign current source via independent rectification.

When normal power is restored, Q is again caused to conduct and the lights are cut off.

This lighting of the lights has caused a drain on battery 6. Assuming that the battery has been discharged to a substantial extent, then the following takes place when the power is restored and the emergency lights go off.

Current flows from voltage level a to b via: R R R Q base-emitter, R and R With transistor Q conducting, additional current paths are created. A second path forms through R, to Q where it joins with the first path. This causes Q to conduct and permits current to flow through: (a) Q, emitter-base to Q emitter-collector, R and SCR gate and (b) Q emitter-collector and pilot light P The path through R and Z establishes a definite voltage at junction b regardless of what the charging voltage is. This definite voltage is important as a reference for Q By means of these paths, the SCR is constantly being fired and thus conducting, which shorts out R and allows a higher current to flow through the battery. Resistors R R and R are for biasing and thus control the voltages and consequent currents to Q base, Q base, and SCR gate to the desired values, respectively. Resistors R R R and R are primarily to limit current. Also R and R being in series with R are part of the bias control of Q When the battery charging having progressed to predetermined point where the battery should now be transferred, as indicated by the charging voltage, to a low charge current rate, the voltage across R has reached a value such that voltage at junction a is at the desired value as to cause Q to conduct. Upon Q conducting, a path R R Q collector-emitter, and R is established. Since the resistance between junctions c and d via Q is negligible, compared to path through R Q and R Q is effectively shorted out and ceases to conduct.

With Q non-conducting, Q loses its bias and turns oflf. This in turn causes: (a) Q; to shut off, extinguishing pilot light P and (b) removes the SCR gate voltage and shuts off the SCR.

Current must now pass through R only, and thus is reduced to a much lower value or trickle rate which may be adjusted to desired value by varying the resistance R Immediately upon switching to lower trickle charge rate, there is an immediate drop to a lower charging voltage across the battery (and R Q continues to conduct while the remainder of the transistors and the SCR remain off or non-conducting. This ability to resist changing back to the high charge condition (Q on and Q off) is due to the inherent nature or characteristic of the circuit used, in conjunction with associated resistors, and is referred to as circuit hysteresis. Although the voltage to Q base has been slightly reduced and is below its original required firing voltages, it still continues to conduct. It will continue to conduct unless the voltage drops to a value below that required to turn on Q This drop below the turnoff voltage will occur only when the battery has discharged below the predetermined value because of charging failure and battery self discharge, or discharging of the battery into the load or emergency lights.

A power failure will cause the emergency lights to be energized and the charger shut off.

Cit

The immediate drain from the battery for the lights, removes the surface voltage from the battery and thus the voltage at junction a is less than the conducting voltage of Q which causes it to shut off. Q then resumes conducting. However, because there is no charging current present, there is no current flow through Q and Q Accordingly the SCR and pilot light, P remain off.

The Zener diode, Z, has a fixed permanent voltage dropV Because of this, it frequently used as a voltage regulator. Thus when Q is conducting there is a definite and fixed voltage at every point between and through Q path. At point d, there is a voltage of This voltage is also the same at e. Thus the emitter of Q, at point 3, is always at the definite voltage of Now assume the pot R has been adjusted so that it will have a null or zero point at a certain battery voltage equal to +0.3 v., or assume E=3.0 volts, then the zero point would be 3.3 v. (The +0.3 v. is the normal voltage increment required to turn on the transistor.)

Naturally as a battery is charged, it will start at less than this null voltage. As it becomes charged, the voltage at point 1 approaches the null point. Then at the null point Q fires.

Without Zener Z to regulate and thus establish the fixed voltage of at d and e, these points too would increase somewhat as battery voltage rises. Thus it would be nearly impossible to obtain 0.3 v. increment for the null point to occur. At least a definite switching voltage would not be possible without a definite fixed voltage E at the emitter of Q Once Q turns on, Q is shut off due to to much less resistance being in the Q circuit and greatly reducing the current available for the base-emitter or Q the great majority of current passes collector-emitter of Q While the battery charging voltage will be reduced below the original turning-on voltage, the fact that Q stays on and Q remains off is due to the hysteresis. Assuming that the battery was partially drained while the transistors were in this position (battery drain such as inadequate trickle charge), when the battery had dropped to a certain voltage at the end of the hysteresis limit, then Q would come on and shut off Q FIG. 2 shows a modification using a transistor rather than an SCR. Other than the portion shown, it is identical with FIG. 1.

The base of transistor Q is connected to the collector of Q its emitter to line 12, and its collector to the bases of transistors Q and Q and through resistors R to the collectors of these transistors. The resistance R is connected in parallel with transistors Q and Q,.

It the battery has been discharged and is to be recharged at a high rate, current flows from voltage levels a to b via: R R Q base-emitter, R and R With transistor Q conducting, additional current paths are created. A second path is formed through R to Q where it joins with the first path. This causes Q to conduct and permits current to flow through Q; to and through pilot light P Q, is not conducting because Q has placed an effective short between Q base and emitter. Thus the base current for Q from battery-through R is shunted through Q collector-emitter.

The path through R and Z establishes a definite voltage at junction 11 regardless of what the charging voltage is. This definite voltage is important as a reference for Q Q is biased via R from is collector and thus permitting Q; to conduct. With Q conducting, R is shorted out and allows a much higher charging current to flow through the battery. Resistors R R7 and R are primarily for biasing their respective transistors, while the remaining resistors are primarily to limit current flow.

When battery charging having progressed to a predetermined point where the battery should now be transferred to the low charge current rate, the voltage across R has reached a value such voltage at junction a is at a desired value so as to cause Q to conduct. Upon Q conducting, a path R R Q collector-emitter, and R is established. Since the resistance between junction c and d via Q is negligible, compared to the path through R Q and R Q is effectively shorted out and ceases to conduct.

With Q non-conducting, Q loses its bias and turns 01f. This in turn causes: (a) Q; to shut off, extinguishing pilot light P Q is biased via R and turns on to conduct current to and through R Under this situation the base voltage of Q, is reversed. With Q losing its bias, it shuts off and would shut off Q6, except for bias via R Current is now reduced to a much lower value for trickle rate which may be adjusted to any desired value by varying the resistance of R The larger the resistance, the lower the changing rate upon switching to a lower charging rate, Q and Q continue to continue to conduct while the reamainder of transistors remain off or nonconducting.

If a power failure causes the load to be energized and the charger shut off, the lower battery voltage after use causes Q to revert to its non-conducting state while Q returns to conducting state when normal power is restored and charging resumes.

Inasmuch as the SCR and transistors act purely as solid-state relays or remote switches, a relay of suitabie design could be used in place of these items. In models built using a relay, a current sensitive relay was used- 0.35 watts, 400 ohms. Such a relay usually has low power contacts and thus in some instances it would be used to trigger another relay which would have heavier contacts required for higher currents. As shown in the drawing, FIG. 3, the pilot light is connected at the junction of the diode and contacts G instead of an additional transistor stage previously used, as Q; in the SCR circuit.

The switching On and Oil of the transistors is the same as in the previous figures, the only difierence being that Q feeds the sensitive relay coil G instead of the SCR gate with its voltage dropping resistor. Obviously the pilot light is on only when the relay contacts are closed since there can be no reverse current flow through the diode.

To manually place the battery on high charge rate regardless of battery voltage, opening of S in the emitter circuit of Q prevents the Q circuit from effectively shorting out Q circuit, and thus Q remains conducting for high charge regardless of battery voltage.

Temperature compensation of the battery voltage at which the circuit should switch from high to low charge may be achieved by inserting a thenmistor in the sensing circuit. By selecting the correct thermistor, compensation for an increase in temperature by switching at a lower battery voltage is achieved.

The use of a breaker as a current limiting device which will automatically reset itself when the current overload has been removed is preferably to normal fusing and manual reset breakers.

In circuits exceeding the approximately 70 volts necessary to ignite a neon light bulb, such a light bulb with suitable current limiting resistor may be used to shunt a current limiting device to indicate and signal an alarm when the current limiting device is open and non-conducting.

While we have described herein some embodiments of our invention, we wish it to be understood that we do not intend to limit ourselves thereby except within the scope of the claims hereto or hereinafter appended.

What is claimed is:

1. In a battery charging arrangement having two conductors for connection to the terminals of a battery and a direct current source, first valve means in one of said conductors, a control circuit for said first valve means connected between said conductors and including means responsive to the reduction of the voltage of the battery below a predetermined amount to render said first valve means conductive, said control circuit further including a second valve means operative when conducting to render said voltage-responsive means inoperative, whereby said first valve means in rendered non-conductive, said circuit having a substantial impedance, and voltage-dependent valve means connected across said conductors in parallel with said second valve means to regulate the voltage at which said second valve means becomes operative.

2. In combination with an arrangement as claimed in claim 1, a source of direct current and a battery connected to said conductors, a load, and means, responsive to the failure of the direct current source, to connect said load to said battery.

3. In an arrangement as claimed in claim 1, a relatively high resistance connected in parallel with said first valve means.

4. In a battery charging arrangement having two conductors for connection to the terminals of a battery and a direct current source, first valve means in one of said conductors, a Schmitt trigger circuit connected between said conductors and including means responsive to the reduction of the voltage of the battery below a predetermined amount to render said first valve means conductive, said circuit including a second valve means operative when conducting to render said voltage-responsive means inoperative, whereby said first valve means is rendered non-conductive, and a voltage-dependent Zener diode connected across said conductors in parallel with said second valve :means to regulate the voltage at which said second valve means becomes operative.

5. In an arrangement as claimed in claim 4, a relatively high resistence connected in parallel with said first valve means.

References Cited UNITED STATES PATENTS 3,018,432 1/ 1962 Palmer.

3,123,759 3/1964 Grey 32040 3,160,805 12/1964 Lawson 320--39 3,281,638 10/1966 Crawford 32040 3,281,639 10/1966 Potter et a1. 32039 X 3,310,729 3/1967 Burgess et al. 323-22 X JOHN F. COUCH, Primary Examiner.

STANLEY WEINBERG, Assistant Examiner.

U.S. Cl. X.R. 32322, 38