US3106673A

US3106673A - Regulating device for electric generators

Info

Publication number: US3106673A
Application number: US73703A
Authority: US
Inventors: Domann Helmut
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1959-12-11
Filing date: 1960-12-05
Publication date: 1963-10-08
Anticipated expiration: 1980-10-08
Also published as: GB964503A; JPS372277B1; US3210645A; DE1128006B

Description

Oct. 8, 1963 H. DOMANN REGULATING DEVICE FOR ELECTRIC GENERATORS Filed Dec. #76.

States atent Ohice 3,106,673 Patented Oct. 8, 1963 ELECTRIC The present invention concerns a regulator arrangement for low-voltage generators which may be driven at greatly varying speeds. This applies particularly to the lighting generators of motor vehicles.

Regulator arrangements of the type set forth are known which comprise a transistor connected in the exciter circuit of the generator, the collector of the transistor being connected with one end of the exciter winding of the generator, the base of the transistor being connected with the operable contacts of an electromagnetic relay the energizing coil whereof is connected so as to be passed by a current varying in proportion with the varying output voltages of the generator. In such conventional regulator arrangements the contacts of the electromagnetic relay controlled by the output voltage which is to be regulated, are moved to open position whenever the output voltage of the generator is about to exceed a pre determined normal value. Therefore, the relay contacts are located in a line connecting the base of the transistor with that one of the output terminals of the generator which is also connected with the collector of the transistor.

It has been found that an arrangement of this particular type easily causes contact troubles because at the moment when the cooperating contacts are separated a very considerable voltage may appear therebetween. Moreover, it is rather difficult in such an arrangement to provide for a rapid transition between energized and de-energized condition of the relay so as to assure a sufficiently high frequency of the switching operation of the relay.

It is therefore a main object of the present invention to provide for a regulator arrangement which avoids the above mentioned difficulties.

It is another object of the invention to provide a regulator arrangement of the general type set forth in which the wattage to be handled at the contacts of the voltagedependent relay is greatly reduced as compared with the corresponding condition in conventional arrangements.

It is still another object of the invention to provide for a regulator arrangement of the type mentioned in which a high switching frequency of the relay is assured irrespective of the actual inductance of the exciter winding of the generator so that a uniform type of regulator may be utilized in connection with generators of diiferent capacities.

It is still another object of this invention to provide for a regulator arrangement of above type which permits also the incorporation of a tell-tale lamp indicating whether a battery connected in the output circuit of the generator is being changed or not, the particular lamp being supposed to be extinguished when the output voltage of the generator reaches the actual voltage available at the terminals of the battery so that with such voltage or a higher voltage the generator is capable to charge the battery.

With above objects in view, a regulator arrangement for a low-voltage generator operable at varying speeds and having an output circuit and an exciter circuit, comprises, according to the invention, in combination, transistor means having an emitter electrode and a collector electrode connected in series with the exciter circuit of the generator, and having a base electrode connected with of a motor vehicle,

with the exciter winding 15 thereby to the negative terminal of the generator output circuit so transistor conductive; an

a the emitter-base circuit of said transistor means and including normally open contact means; and control means for said contact means, operatively connected with said generator output circuit for changing said contact means from open to closed condition and for thereby rendering said transistor means non-conductive whenever the generator output voltage exceeds a predetermined value.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing, in which:

lFlG. l is a circuit diagram of a lighting plant of a motor vehicle, including a regulator arrangement according to the invention;

FIG. 2 is a graph illustrating the regulating procedure;

FIG. 3 is a graph showing the currentvoltage characteristic of a non-linear conductor element provided in the circuit of FIG. 1; and

FIG. 4 is a graph illustrating the voltage-current characteristic of a generator controlled by the regulator arrangement according to the invention.

FIG. 1 illustrates by way of example the lighting plant not shown. The plant comprises a three-phase alternating current generator 10 which has three stator windings 11, 12 and 13 and an exciter winding 15 carried by a rotary armature not shown. Also the means for driving the rotor are not shown. Each of the stator windings 11, 1-2 and 13 is connected, respectively with one of three pairs of rectifiers 16 in a well known manner. The rectifier arrangement is connected between ground and a positive output line 18 which leads across a low-resistance resistor 19 to the positive terminal of a battery 20. The actual regulator arrangement according to the invention is shown within the dotted line frame R. A switch 23 is provided in the line 22 conmeeting the terminal 33a with the positive terminal of the battery 20. By operating the switch 23 not only the regulator arrangement but also all those components or devices of the vehicle which are to be operated electrically and which are symbolized by the block 25, e.g., the ignition system, signaling means etc., can be supplied with electrical energy.

The actual regulator arrangement R comprises, first of all, a power transistor 30 of the p-n-p-type. The emitter electrode thereof is connected by a line 31 with the'positive connection 22 mentioned above. The emitter-collector circuit of the transistor 30 is connected in series of the generator 10, the other end of the winding 15 being connected to ground and battery 20. The collector of the transistor 30 is additionally connected with a silicon diode 32 the input electrode whereof is also connected with ground through the terminal 33 of the regulator arrangement R. As will be explained further below, the diode 32 is designed to protect the transistor 30 against excessive voltages which are to be expected to appear when during the regulation procedure described below the transistor is changed briefly from its conductive condition to its non-conductive condition.

According to the invention a pair of normally open cooperating contacts is connected in parallel with the emitter-base circuit of the transistor 30. These contacts form part of an electromagnetic relay which has an energizable coil 35 connected between the

terminals

33 and 33a so as to be passed by a current J which depends upon the rectified output voltage of the generator 10 and which is usually proportional thereto. The above-mentioned pair of contacts of the relay consists of a switch arm 36 operated by the armature, not shown, of the coil 35, and of a stationary contact 37. The switch arm 36 is connected with the line 31 While the contact 37 is connected with the base electrode of the transistor 30. The contact 37 and thus also the base electrode of the transistor is connected across a fixed resistor 38 with the movable tap of a potentiometer 40 one end of which is connected to the above mentioned coil 35 of the relay while the other end is also connected to the grounded terminal 33. For reasons stated further below, a second stationary contact 42 is provided for cooperation with the switch arm 35. However, the distance between the

relay contacts

42 and 37 as well as the distance between the not shown armature and the iron core of the relay, not shown, are so chosen in relation to the action of a return spring, not shown, controlling the relay armature, that the switch arm 36 may be disengaged from the contact 42 whenever the rectified output voltage of the generator exceeds the battery voltage which amounts to about 12.6 volts when the battery 2t is operating under load; however under the just mentioned condition the switch arm 36 would not yet move sutliciently to engage the stationary contact 37 but would be held in an inbetween position between the two

stationary contacts

37 and 42 as long as the generator output voltage remains below a predetermined normal value of about 14 volts which is the desired voltage to be determined by the action of the regulator arrangement.

The second stationary contact 42 is connected by a line 43 via terminal 33b with a tell-tale lamp 45, the other terminal whereof is connected to ground. This lamp 45 is intended to light up when the switch 23 is closed while the output voltage of the generator is still below the battery voltage which depends upon the degree of its being discharged or charged. However, the tell-tale lamp 45 is to be extinguished whenever a load current I flows from the rectifiers 16 via line 18 to the battery 20, said load current constituting the charging current for the battery.

For the purpose of protecting the rectifier arrangement 16 and the stator windings 11, i2 and 13 of the generator against overload a current limiting arrangement is provided which causes a considerable reduction of the output voltage of the generator whenever the load currentl flowing through the line 18 and through the resistor 19 exceeds a predetermined maximum value. The current limiting arrangement comprises a second coil portion 47 of the above described relay which second coil portion 47 acts on the armature, not shown, and on the switch arm 36 in the same manner as the above-described voltage controlled main coil 35. As can be seen, the second coil 47 is arranged in an auxiliary circuit including a germanium semi-conductor 48 arranged in parallel with the resistor 19.

The operation of the above described regulator arrangement will be best understood by starting with the consideration that, e.g., upon starting of the engine, the generator 10, having been at a standstill, is first caused to start rotation of its rotor under the action .of a driving motor not shown in the drawing. Since for starting the just-mentioned motor the switch 23 has to be moved to closed position, a strong exciter current 1., can be supplied to the exciter winding 15 of the generator through the lines 22 and 31 and through the emitter-collector circuit of the transistor 30 which under the prevailing conditions is in conductive condition. The just mentioned strong exciter current J causes a rapid build-up of a direct current field rotating with the rotating armature of the generator. Consequently voltages are produced in the stator windings 11, 12 and 13 which increase the more rapid the higher is the rotary speed of the generator.

FIG. 2 illustrates in graph form the increase of the rectified output voltage U A of the generator appearing between the positive output line 18 and ground, in relation to time it. As long as the output voltage U remains smaller than the battery voltage U marked in FIG. 2 as amounting to 12.6 volts, the current 1 flowing through the voltage responsive coil 35 of the relay is not yet able to lift the switch arm 36 from its cooperating contact 42 with which it is held normally in engagement by spring means not shown. Therefore, the tell-tale lamp 45 is supplied with electric energy from the battery 20 via line 43, contact 42, switch arm 36, line 22 and closed switch 23. Thus the light of lamp 45 indicates that the generator output is not yet able to charge the battery or, in other words, the battery is discharging. When, however, the generator output voltage U at the time A has risen enough to exceed the battery voltage U then the current I, increasing in proportion with, or any way depending upon, the voltage U sufiices to lift the switch arm 36 from the contact 42 so that the lamp 45 is extinguished and thus indicates that the battery is now being charged. However, the transistor 30 still remains in conductive condition because the switch arm 36 is for the moment in an intermediate position in which it contacts neither the contact 42 nor the contact 37. The transistor 30 is rendered non-conductive only when the generator output voltage U A reaches, at the moment marked t a predetermined value U for normal operation, e.g., 14 volts. At this voltage the current I, suffices for moving the switch arm 36 into engagement with the stationary contact 37 whereby the emitter-base circuit of the transistor 30 is shunted, or, in other words, the potential of the base electrode of the transistor 30 is raised to such an extent that the transistor cannot remain conductive any longer. Thus, as is also shown in FIG. 2, the current I drops steeply to a value close to zero and the exciter current 1 drops accordingly. This drop of the exciter current results in a corresponding collapse of the magnetic field produced by the winding 15, and the resulting self-induced current is permitted to flow through the secondary circuit containing ground, terminal 33, rectifier diode 32, terminal 33 and winding 15. Simultaneously with the collapse of the magnetic field of the exciter winding 15 also the output voltage U of the generator drops. Due to the specific arrangement of the contacts of the relay and the parameters of the relay the desired effect is assured, namely, the effect that upon a small drop of the generator output voltage U A the switch arm 36 disengages itself from the main operative contact 37 whereby the transistor 30 is returned to its original, normal conductive condition. Upon this slight drop of output voltage the transistor current I is started again as can be seen in FIG. 2. Thereby the magnetic field of the exciter winding 15 is rapidly returned to its previous value so that the whole cycle, just described, repeats periodically as indicated by FIG. 2, without, however, the switch arm 36 being able to return into engagement with the second contact 42.

Since during conductivity of the transistor 30* the potential diiterence between its emitter and base amounts to only about .3 to .5 volt, evidently the wattage to be handled between the

contact members

36, 37 during the switching operations is kept at an extremely low value, particularly also because the resistor 38 connected in circuit with the base electrode of the transistor and with the contact 37 can be chosen so as to have a comparatively large resistance. It can be seen also that in addition the particular arrangement of the second relay contact 42 results in a reliable control of the tell-tale lamp 45 without requiring for the control of this lamp a separate relay as is customary in known arrangements.

A further remarkable advantage of the arrangement described above consists in the fact that the frequency of the regulatory voltage changes eifected by the switching movements of the

contact members

36 and 37, does not depend upon the speed of the build-up and collapse, respectively, of the magnetic field in the generator. As can be seen, as soon as the switch arm 36 engages the stationary contact 37 a current is able tofiow through this pair of contacts which is slightly greater than the base current flowing during conductivity of the transistor through the resistor 38 and through the emitter-base circuit of the transistor. This slight increase of current produces across that portion of the potentiometer 40 which is located between the grounded terminal 33 and the movable tap 39 a voltage drop Which causes the current J flowing through the relay coil 35 to decrease slightly. As soon as the magnetic field produced by the coil 35 has followed this decrease of current, the switch -arm 36 already disengages itself again from the contact 37. Thus, a vibratory or oscillatory operation of the switch arm 36 is created which results in a very accurate voltage regulation and entails the further advantage that the regulator arrangement can be used for generators of diflferent capacities. Moreover, the adjustability of the movable tap 39 of the potentiometer 40 makes it possible in an easy manner to adjust the frequency of the regulatory voltage changes to the requirements of different generator sizes or types.

The current limiting arrangement mentioned further above and comprising the resistor 19, the second relay coil 47 and the germanium semi-conductor 48 is designed to cancel out the above-described voltage regulation as soon as the line '22. is connected with current consuming devices 25 which have so low a resistance that, if the output voltage U of the generator were left unchanged, a load current 1;, would result which might overload thegenerator 10. In the arrangement as shown the load current J produces across the resistor 19 a voltage drop U which, as it increases, produces the flow of a control current J across the second relay winding or coil 47. The parameters of this auxiliary circuit may be chosen for instance so that a suitable control current I is caused to fiow when the voltage U exceeds a value of about .25 volt. This will depend greatly upon the characteristic of the semi-conductor 48. The graph of FIG. 3 illustrates a typical characteristic of a semiconductor rectifier 4 8 which displays at a potential difierence U of .25 volt between the electrodes of the semiconductor a very distinct break. A germanium semiconductor of this type contains a high percentage of copper atoms in an alloyed zone produced by addition of indium in an n-germanium disc, and this type of semiconductor is particularly well suited for the purpose in question because they not only display a very sharp break in their current-voltage characteristic, but are capable of reaching this break already at very low values of the potential difference U existing between their electrodes.

For the purpose of illustration, the graph FIG. 4 shows the voltage-current characteristic of a direct current generator having a capacity of 400 watt cooperating with a 12 volt battery. A curve 50 indicating 400 watt output is shown. The characteristic indicating the regulation of the output voltage U in relation to increasing load currents I shows that the regulator arrangement above described causes the regulated voltage U of the generator to drop steeply as soon as the load current I increases beyond 27 amperes. The product of 14 volts with 27 amperes is close to 400 watts. The sharp break in the characteristic shown in FIG. 4 is desirable because in this manner the capacity of the generator can be utilized most effectively and economically.

It will be understood that each of the elements described above or two or more together, may also find a useful application in other types of regulator arrangements for generators differing from the types described above.

While the invention has been illustrated and described as embodied in regulator arrangement for low-voltage generator operable at varying speeds, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed and desired to be secured by Letters Patent is:

1. Regulator arrangement for a low-voltage generator operable at varying speeds and having an output circuit and an exciter circuit, said arrangement comprising, in combination, transistor means having an emitter electrode and a collector electrode connected in series with the exciter circuit of the generator, and having a base electrode connected with the generator output circuit so as to normally render said transistor conductive; relay means having coil means and a first control resistor connected in series therewith, the resulting series combination being connected with the generator output circuit for being energized by a predetermined current depending upon the varying output voltage of the generator and controlled by said first control resistor, and normally open contact means operable by energization of said coil means by said predetermined current and connected in parallel with the emitter-base circuit of said transistor means so as to render said transistor means non-conductive when said contact means are changed to closed position upon energization of said coil means depending upon a predetermined value of said generator output voltage, a second control resistor being connected between said base electrode and a junction point within said seriescombination for determining the potential of said base electrode required for rendering said transistor means conductive.

2. An arrangement as claimed in claim 1, wherein said first control resistor is a potentiometer having a movable tap, and wherein said tap is said junction point connected to said second control resistor.

3. An arrangement as claimed in claim 1, wherein said relay means include a tell-tale lamp and wherein said contact means comprise a movable contact member connected to said emitter electrode and operable by energization of said coil means, and a first and a second stationary contact alternatively engageable by said contact member, said first stationary contact being connected to said base electrode and adapted to be engaged by said movable contact members only when said coil means are energized by a predetermined minimum value, said second stationary contact being connected with said tell-tale lamp and adapted to remain engaged by said movable contact member and to keep thereby said lamp energized until said coil means are energized by a current exceeding a second predetermined amount still below said predetermined value.

4. An arrangement as claimed in claim 1, wherein said relay means include second coil means for operating saidcontact means, control means operatively connected with said generator output circuit for delivering a control voltage therefrom in proportion to a load current flowing in said output circuit, and circuit means connecting said second coil means and said control means, and including non-linear conductor means for causing energization of said second coil means when said control voltage exceeds a predetermined value, whereby said normally open contact means are changed to closed position by energization of said second coil means and said transistor means are rendered non-conductive whenever the load current in said output circuit causes said control voltage to exceed said predetermined value thereof.

5. An arrangement as claimed in claim 3, wherein said relay means include second coil means for operating said contact means, control means operatively connected with said generator output circuit for delivering a control voltage therefrom in proportion to a load current flowing in said output circuit, and circuit means connecting said second coil means and said control means, and including non-linear conductor means for causing energization of said second coil means when said control voltage exceeds a predetermined value, whereby said normally open contact means are changed to closed position by energization of said second coil means and said transistor means are rendered non-conductive whenever the load current in said output circuit causes said control voltage to exceed said predetermined value thereof.

References (lited in the file of this patent UNITED STATES PATENTS FOREIGN PATENTS Austria May 25,