US2940034A - Automatic voltage regulator - Google Patents

Description

June 1 TUNEiKICHI KUSHIGEMACHI ET AL 2,940,034

AUTOMATIC VOLTAGE REGULATOR Filed Jan. 16, 1957 3 Sheets-Sheet 1 v D H w I B x m 8 1 1 2fm J. K, I X M 2 1. M m R I x 1 n A s 0 i n T 9 T w L B i s g p P1 4 M 7M June 1960 TUNEKICHI KUSHIGEMACHI ET AL 2,940,034

AUTOMATIC VOLTAGE REGULATOR Filed Jan. 16, 1957 3 Sheets-Sheet 2 J1me 1960 TUNEKICHI KUSHIGEMACHI E L 2,940,034

AUTOMATIC VOLTAGE REGULATOR 3 Sheets-Sheet 3 Filed Jan. 16, 1957 United States Patent 6 AUTOMATIC VOLTAGE REGULATOR Tunekichi Kushigemachi and Yoshiyuki 'Watanabe, Tokyo-t0, Japan, assignors to Katsurogawa Denki Kabushiki-Kaisha, Tokyo-to, Japan Filed Jan. 16, 1957, Ser. No. 634,550

1 Claim. (Cl. 32311) This invention relates to an automatic voltage regulator capable of carrying out automatic regulation of an electrical voltage so as to maintain said voltage at a substantially constant value by means of rapid compensation of variation of said voltage.

An essential object of this invention is to obtain an improved voltage regulator having only the advantageous characteristics without accompanying disadvantages of the usual mechanical voltage regulator such as induction regulator, slidable regulator and the like or of the usual electrical voltage regulator such as magnetic amplifier, ferro-resonance type regulator and the like.

The mechanical voltage regulator as described above has advantageous characteristics that it does not disturb wave form of the output voltage, it is scarcely affected by frequency variation, and its regulation is not astatic, but has disadvantages that regulation settling takes relatively long time, for instance, about 3 seconds at the shortest, because the regulation is carried out by a voltage relay through a driving motor and a speed reduction device, said time being seconds in normal condition and about 40 seconds in the case of induction regulator.

On the other hand, the electrical voltage regulator as described already has an advantage that settling time of regulation is very short, for instance, shorter than about 0.2 second, but has disadvantages that it is liable to disturb wave form of the output voltage and to be affected by frequency and aging, and its efficiency is relatively low.

The voltage regulator of this invention, as will be minutely described hereinafter has only the advantages of the usual voltage regulators without accompanying the disadvantages as described above. That is to say, the voltage regulator of this invention has advantages that settling time of regulation is almost equal to that of the electrical voltage regulator, influences caused by wave form and frequency are very little, construction and manufacture thereof are very simple and cheap, durable.

Said objects and other objects of this invention have and it is very 7 been accomplished by an improved automatic voltage regulator which comprises a voltage adjustor, an electric motor having a rotor applied with a torque corresponding to variation of the output voltage to be regulated at a constant value, a compensating device coupled with the shaft of said rotor and capable of generating a counter torque directed in reverse to that of the torque of said rotor, and a brush supported so as to automatically slide along the sliding surface of said adjuster in accordance with difference between the above-mentioned two kinds of torques so as to regulate said output voltage.

The principle of the voltage regulator as described above can be embodied in the following three systems.

(a) First system which comprises a slidable type transformer, an electric motor, core of the former and stator of the latter being made of a common iron core and the rotor of said motor being applied with a torque which varies in accordance with voltage variation of the pri- Fatented June 7, 1960 mary circuit, a spring supported so as to generate a counter-torque against the torque of said rotor, and a brush which is coupled with the shaft of said rotor and can he slid along the coil of the above-mentioned transformer.

The voltage regulator according to this system consists of a combined mechanism composed of three elements, that is, a slidable main transformer of usual voltage regulator type, a driving motor and a voltage relay for detecting the variable output voltage. In other words, the voltage regulator of this system acts as transformer, driving motor and voltage relay so that it is very simple in its construction, easy in its manufacture, very cheap in its cost and the settling time of regulation is very short.

(b) The second system, in which a spring is attached to the rotor shaft of a commutator motor, said motor be ing made so as to apply a torque to each of the rotor of said motor and the spring, said both kinds of torques being directed in reverse each other, a direct current superposed with a ripple current is applied to said motor, and a brush directly coupled with the rotor shaft of the motor is made to slide automatically along the contact surface of a slidable transformer so as to maintain the output voltage of said transformer at a predetermined value. According to this system, since the driving motor is a commutator motor, starting torque of the regulator is very large, whereby operation error due to frictions at the bearings and the other parts and voltage deflection of the output voltage are remarkably reduced. Moreover, since a direct current voltage is applied to the motor, unfavourable influences and noise caused by frequency can be reduced, and moreover since said direct current contains a suitably superposed ripple current, the rotor accepts a minor vibration, whereby starting is made very easy, so that operation error and voltage deflection are remarkably reduced and bearings of high quality are made unnecessary.

(=c) The third system which is almost same with the second system except only that the spring in the second system is substituted with an electrical motor having a constant torque.

In this system, two commutator motors are connected to a common shaft and these motors are, respectively, applied with a constant current and a variable voltage, both torques of said motors being made reverse each other.

The third system has various advantages which are almost same with those of the second system. In the second system, regulation is astatic and coincidence of the torque characteristic of the spring with that of the motor is necessary, but in the third system, regulation is not astatic and the above-mentioned coincidence is'not necessary.

The novel features which are believed to be characteristics of the present invention are set forth with particularity in the appended claim, but the present invention, both as to its construction and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, in which the same members are indicated by the same marks and in which:

Fig. 1(a) is a schematic plan view of an example of this invention.

Fig. l(b) is a side view of the example in Fig. 1(a).

Fig. 2 is a schematic connection diagram of the example in Figs. 1(a) and l(b).

Fig. 3 is a schematic connection diagram being equal to the diagram in Fig. 2, except reverse connection of the primary and secondary terminals.

Fig. 4(a) is a schematic side view of another example of this invention.

Fig. 4(b) is a plan view along the line IV(b)IV(b) in Fig. 4(a).

- Fig. 5. is a schematic connection diagram of the example'in Figs. 4(a) and 4(b).

Fig. 6 is a schematic connection diagram of a further example of this invention. ,Fig. 7 is a schematicconnection diagram of'a still further example of this invention.

Referring to Figs. 1(a), 1(b) and 2, the voltage regulator comprises a single phase commutator motor M having a rotor AM, a commutator C, carbon brushes CB,

a stator core W, and a transformer coil SC wound around said core W, said coil SC and core W forming an autotransformer. I V The output voltage of the transformer co'il SC is made to be regulated by sliding of a carbon brush B along the coil SC, said brush sliding being efiectuated by a brushholder EH which in turn is attached to the shaft S of the rotor AM.

When a primary voltage PV is applied to the primary terminals-p and p secondary voltage or output voltage SV is obtained at the secondary terminals s and s and a torque occurs in the commutator motor M by mutual action between the magnetic flux due to the rotor current of said motor and the magnetic flux due to the exciting current in the coil SC, said torque being made to vary in proportion to the primary voltage PV. According to this invention, said electrical torque is made to balance with a mechanical torque of a spiral spring MS which is attached to the shaft of the motor M.

Accordingly, when the torque characteristic of the rotor AM, said characteristic corresponding to the rotor position, is adjusted so as to be coincident with that of the spiral spring M8, the secondary voltage will be automatically maintained at a constant value without rela tion to variation of the primary voltage. The mechanism shown in Figs. 1(a), 1(b) and 2 is provided with a motor frame X, springs AS for absorbing vibration, a variable resistor VR for adjusting torque of the motor andstoppers ST for stopping the brush holder BH at its both limits.

In; the embodiment of this invention, it may be possible to use a rotor of squirrel cage type, but it is unsuitable for practical use because of low starting torque thereof. On the contray, it has been found, according to our experimental results, that when a rotor of commutator type isused, regulation torque is 3 kg. per cm. in the case of an automatic voltage regulator of 300 va. and deflection of output voltage is less than about :2% inthe case of. use of usual bearings of oilless metal type. Accordingly, operation error due to friction is almost negligible. ,Of course, since there is an air gap in the magnetic circuit of the stator, some decrease of power factor is unavoidable. However, its efficiency is remarkably higher than that of any pure electrical regulator and settling time of regulation is very short, for example, settling time of the secondary voltage SV is less than 0.2 second in the case of 50% variation of the primary voltage.

The voltage regulator illustrated in Figs. 1(a), 1(b) and 2 may be modified so as to be exchanged condition of the primary and secondary sides with same operation and effects, as shown in Fig. 3.

An example of the second system of this invention is shown in Figs. 4(a), 4(b) and 5, in which the voltage regulator comprises a commutator type single phase motor M, said motor comprising a rotor AM, a commutator C, a field coil F and carbon brushes CB being in contact with said commutator C, a brush holder BH supported by the shaft S of the rotor AM, a slidable type main transformer MT having a transformer coil SC, a

"5 attached to the shaft S and which operates to produce a counter-torque against the electrical torque of the motor M, a frame X for supporting the above-mentioned members, rectifier bridge devices K and K adjustable resistors R and R for the compensation of temperature coefficient, and auxiliary transformers T and T In the voltage regulator illustrated in Figs. 4(a), 4(b) and 5, when a primary alternating current voltage PV is applied to the primary terminals p and p a secondary voltage SV appears at the secondary terminals s and s in this case, the direct currents'rectified at the rectifier devices K and K pass, respectively, through the rotor AM and the field coil F of the motor M, so that motor torque varies in accordance with variation of the primary voltage PV. Accordingly, when the torque characteristic of the motor M and the counter-torque characteristic of the spring SP are suitably adjusted, the secondary voltage SV can be maintained at a constant value due to automatic shifting of the brush holder BH.

in the above regulator, if an alternating current voltage is directly applied to the motor M, miscellaneous noise is liable to occur and the secondary voltage S! varies in proportion to frequency variation because of inverse relation of the motor torque to frequency variation.

The above-mentioned unfavorable effect due to frequency variation can be avoided by applying direct currents obtained by the rectifier devices K and K respectively, to the rotor and field stator, as shown in Fig. 5.

However, since both the magnetic flux generated at thestator by the rectified field current and the current passing through the rotor are almost constant and contains scarcely pulsating component, bearing friction of the motor during rotation of the rotor is only the static friction. On the other hand, since there is some unbalance in the air gap between the stator and rotor, unbal anceof the attraction force between the rotor and stator occurs and the rotor is attracted towards the portion in which air gap is reduced, whereby frictional resistances of the bearings and deflection of the output voltage is increased.

For avoiding the above-mentioned disadvantages, according to this invention, an auxiliary transformer T 2 is connected in series to the rotorcircuit of the motor M as shown in Fig. 5 or to its field circuit, whereby a direct current superposed with a ripple current ismade to pass through said circuit. Accordingly, when the amplitude of said ripple current is selected so as to give no effect to the operation character, but to give a slight vibration to the rotor of the motor M, the rotor'shaft can be maintained in a floating condition, whereby the static friction is converted into movable friction. On the other hand, the brush B supportedv by the brush holder EH accepts minor vibration, so that the static friction of said brush becomes movable friction. As its results; rotary frictional resistance being an important factor for voltage regulator reduces and deflection of output voltage reduces remarkably.

Actual experiment of the illustration in Figs. 4(a), 4(b) and 5: i 1

When the number of segments of the commutator and torque of the rotor are, respectively, selected as 48 and 3 kg. /cm., deflection of the output voltage is above about i8% in the case of exciting current having no superposed ripple current. However, when an exciting current superposed with a ripple current by an auxiliary transformer T is used, deflection of the output voltage can be reduced within'about i2% and particularly within about il% in the case of increase of the commu tator segments.

Examples of the third system of this invention are shown in Figs. 6 and 7, in which two commutator motors M and M having a common shaft are used instead of use of the spring SP in the illustration in Figs. 4(a), 4(b) and 5.

The motor M comprising a rotor AM; and a field coil F is supplied with a constant current from the output line voltage E of an A.C. generator ACG through a transformer T a rectifier device K and a constant current device KCV such as ballast tube so as to make rotor torque of the motor M in constant, said generator being provided with a field coil F, supplied with an exciting current from exciting terminals B, through a field resistor FR. The other motor M comprising a rotor AM, and a field coil F, is supplied with the circuit voltage from the line voltage B; through a transformer T and the rectifier device K. Connections of the motors M and M, are selected so that both the torques of the rotor AM, and AM, may become reverse each other. According to such construction, both the rotors AM, and AM, are brought in balanced stationary states in case both the torques of the rotors AM, and AM, become equal, that is, in case the secondary voltage is controlled to a rated value.

Accordingly, when, as shown in Fig. 6, the brush for adjusting the resistance of the field resistor FR in the field coil F, of the AC. generator ACG is directly coupled with the motor shaft S so that the rotors AM, and AM, may be brought in balanced states in the case of a predetermined desirable value of the output line voltage B, and said balanced states may be broken in the case of variation of the voltage E, from the predetermined desirable value, the line voltage B, will be automatically maintained at the predetermined constant value. In the above-mentioned unbalanced condition, any one of the rotors AM, and AM, is driven towards any one direction so as to adjust the resistor FR.

Upon restoration of the voltage E to the predetermined value, the rotors stop. According to said system, the voltage E, can be always maintained at a constant value.

Of course, the predetermined value of the voltage E, can be desirably adjusted by adjusting the variable resistors R and R, which are, respectively, connected in series to the rotors AM, and AM,.

The voltage regulator illustrated in Fig. 7, in which primary voltage PV is applied to primary terminals p and p, and secondary voltage SV is taken out from secondary terminals s and s is almost same with the illustration in Fig. 6 except that a slidable type transformer MT is used as line voltage regulator instead of use of the field resistor PR in Fig. 6.

According to this invention, as will be clearly understood from the above-mentioned description in conjunction with the drawings, the brush is directly driven by the shaft of the motor without use of intermediate voltage relay and speed reduction device, so that the regulator of this invention has various advantages that automatic adjustment of the output voltage is very speedy just like any electrical voltage regulator, voltage regulation does not disturb the wave form of the output voltage and is not affected by frequency variation, and the device becomes simple in the construction, easy in the manufacture and cheap in the cost.

While we have described particular embodiments of our invention, it will, of course, be understood that we do not wish to be limited thereto, since many modifications may be made and we, therefore, contemplate by the appended claim to cover all such modifications as fall within the true spirit and scope of our invention.

We claim:

A voltage regulating system comprising, a first corn mutator motor having a stator and a rotor, a second commutator motor having a stator and a rotor, a shaft connecting said rotors, a source of alternating current having a variable voltage, means including circuits connected to said source applying unidirectional potential to one of said motors whereby the motor develops a torque in one direction, means including circuits connected to said source applying unidirectional potential to the other of said motors whereby it develops a torque in an opposite direction, voltage adjusting means for varying the potential of said source, and means actuated by said shaft for alternating said voltage adjusting means in response to the rotated position of said shaft.

References Cited in the file of this patent UNITED STATES PATENTS 1,841,082 Biggs Ian. 12, 1932 2,253,947 Blume et al. Aug. 26, 1941 FOREIGN PATENTS 310399 Great Britain Apr. 25, 1929

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