US2740934A - Electromagnetic converter - Google Patents

Description

April 3, 1956 F. KESSELRING ELECTROMAGNETIC CONVERTER Filed Oct. 3, 1951 2 Sheets-Sheet 2 IN V EN TOR.

United States Patent ELECTROMAGNETIC CONVERTER Fritz Kesselring, Zollikon-Zurich, Switzerland, assignor t0 FKG Fritz Kesselring Geratebau AG, Bachtobel-Wemfelden, Thurgau, Switzerland, a corporation of Switzerland Application Qctober 3, 1951, Serial No. 249,594

Claims priority, application Switzerland Gctober 7, 1950 2 Claims. (Cl. 321-48) My present invention is a continuation-in-part of application Serial No. 237,721, filed July 20, 1951, and relates to an electromagnetic switch. More particularly my present invention relates to an electromagnetic switch or converter, supplying a rectified current, which utilizes a magnetic contactor having a plurality of windings.

It is necessary when switching currents at the rate of 60 cycles per second that the current switched be of relatively low value. If the switched current is greater than one-half an ampere, the contacts melt, become welded, and are torn apart when opened. It is evident that this action soon destroys the contacts, rendering the switch inoperative.

Heretofore in the prior art various tube rectifiers or mechanical motor-driven rectifiers were utilized. The tubes, however, introduce substantial resistance into the conducting circuit which in some situations is highly deleterious and the mechanical rectifier commutates prohibitive currents.

Magnetic switches have considerable ohmic losses as the winding requires many turns to effect a satisfactory closing of the contacts. The dimensions of the magnetic switches and resulting manufacturing costs, due to the problem of effecting a satisfactory closing are in addition unsatisfactory; the dimensions are large in order to provide strengthened lines of force and the costs are great due to the many heavy turns on the winding and due to the large dimensions.

My invention attempts to overcome these difiiculties by providing a circuit containing a magnetic switch with an auxiliary winding which is energized only to aid in the opening and closing. The energization of the auxiliary winding adds to the total lines of force effecting satisfactory opening and closing operations. These compensating lines of force aid the lines of force supplied by a considerably smaller main winding during the portions of the operating cycle when it is desirable for the magnetic switch to effect a change of circuit conditions.

It is then an important object of the present invention to provide a novel electromagnetic switch efi'ecting satisfactory closing and opening of the contacts.

Another important object of the present invention is the provision of a novel switching circuit having substantially no arcing across the contacts.

Another important object of the present invention is to provide a step in the current at substantially a zero value when the contacts are closed.

Another important object of the present invention is the provision of an electromagnetic switch having an additional force aiding the closing winding.

Still another important object of my invention is the provision of a rectifier having a rectifying tube which is operative when the magnetic switch is turned on or 011.

Still another important object of my present invention is the provision of a novel rectifying circuit providing a current step when the contacts are opened.

Further objects and advantages will become evident 2,740,934 Patented Apr. 3, 1956 M upon consideration of the description in conjunction with the figures wherein- Figure 1 is a circuit diagram showing a novel auxiliary winding of my present invention.

Figure 2 is a circuit diagram showing a novel auxiliary winding of my present invention.

Figure 3 is a circuit diagram of a modification of my present invention.

Figure 4 is a circuit diagram of a modification of my present invention.

Referring now to Figure 1, there is shown the circuit of an electromagnetic switch having an auxiliary coil 117 to aid in the closing of the armature 111. The auxiliary coil 117 is wound on the pole 109 of the magnetic switch 107.

The magnetic switch 107 has a second pole 108, an air gap 110, and a main winding 116. The main winding 116 makes contact with the winding 117 and with the pole 109 at point 130.

The poles 108 and 109 are constructed so as to be highly conductive and also magnetizable. The main winding 116 of the magnetic switch 107 is in series with primary winding 103 of the saturable core 102 and the alternating current source 101. In order to decrease the magetizing current flowing in winding 103 or" saturable core 102, a pre-excitation circuit such as the circuit comprising the inductor 105 and D. C. source 106 may be used to supply magnetizing current to winding 104 in a manner well known in the art. The current path proceeds through the primary 103, the main winding 116, through the pole 109, thence through a rectifier and finally through pole 108 and the load 123 back to the source 101. The saturable core 102 saturates at very small values of current and hence almost immediately produces a step in the rising current.

The magnetization of the core 102 produces a positive voltage on the grid 121 of the triode 118 from the tap 122 on the primary 103. The triode 113 is a gas filled triode, whose cathode is connected to the end 126 of the primary 103. The triode 118 receives its plate potential from the direct current source 106 which is applied across a capacitor 119 through a resistor 120. The capacitor 119 is connected across the triode 118 through the coils 116 and 117 described above. The positive pulse on the grid 121 of the triode 118 caused by the change in magnetization of the core 102 ignites the triode 118 causing current flow through the coils 116 and 117.

The auxiliary coil 117 is wound so that current through its windings produce lines of force in the same direction as the lines of force due to the main winding 116. The current through the windings 116 and 117 caused by the firing of the tube 118 is in the same direction as the current in the main winding.

Thus, while the current in the main winding due to the alternating current source 101 is still in the portion of the cycle that is in step, the armature 111 biased by the springs 112 seated in the insulators 113 and 114 is brought down into contact position. The potential from the alternating current source continues to rise so that at the conclusion of the step and the lines of force due to the auxiliary winding, sulficient current flows and flux is induced by the main winding 116 so that the armature remains seated in position.

The capacitor 119 discharges through the tube circuit upon firing by a positive pulse on the grid 121. When the capacitor 119 is discharged the tube circuit ceases to conduct.

Immediately after the capacitor 119 discharges it commences to store energy again from the direct current source 106.

As the current continues to rise through the main winding the-contact acrossthe' poles S and 109 is seated more and more firmly in position.

When the current descends to substantially zero amperes the excitation due to the main winding 116 is not sufficient to maintain the prismatic armature 111 in position and so spring 112 opens the contacts. The tube 118 does not fire on the negative step as a negative pulse appears on the grid 121 inhibiting the firing.

Figure 2 shows a modification of the present invention having the auxiliary winding 149 wound on the pole 142 of the magnetic switch 1140. Magnetic switch 1% is in series with the primary coil 134-, the alternating current source 131 and the load 152. When the alternating current source 131 introduces a rising current, the saturable core 133 of the saturable unit 132 produces a step in the current due to the reversal of magnetization. A voltage or pulse is induced across the taps 135 and 136 of the coil 134. The pulse produced essentially provides the positive plate potential for a gas diode 137 connected from the bus 133 of a direct current source to the tap 135 described above.

The direct current source supplies a plate potential across the diode 137 in the same direction of the pulse which is insutficient to cause the firing of the tube 137. The addition, however, of the voltage due to the change in magnetization of the core 133 produces a sufficient total plate potential to cause the tube 137 to fire.

When the gas tube 137 fires, the direct current buses 138 and 139 have a closed path through resistor the auxiliary winding 14-9 and the portion of the Winding of the coil 134 between the taps 135 and 136. The current from the alternating current source 131 flows through the main Winding 148, the rectifier 151, and thence through the load 152. The additional lines of force produced by the auxiliary winding 149 upon the firing of the diode 137 are of sufiicient strength to cause the move ment of the prismatic armature 144 which is biased on the spring 145 between the insulators 146 and 147. The electromagnetic switch 140 has, in addition to the above components, another pole 141 and an air gap 143.

This procedure is then similar to the one described above in reference to Figure l as the prismatic armature 144 is caused to move when a relatively negligible amount of current is flowing through the main winding 148.

Once the armature 144 is seated in position the still rising current through the main winding 14% continues to increase the pressure of the contacts. With a decreasing current a negative pulse is placed on the plate 153 of the tube 137 which further inhibits the firing. Less copper is needed in the main Winding 148 as the auxiliary current flows only through the auxiliary winding 149.

The modification of the present invention as shown in Figure 3 discloses a circuit containing an electromagnetic switch 172 where the opening of the contacts due to the movement of the prismatic armature 178 is caused by magnetic means and a direct current source is unnecessary for supplying the auxiliary current. When the alternating current source 161 initiates a rising current, it flows through the winding 164 on the saturable core 162, the main winding 175 of the electromagnetic switch 172, the rectifier 184 connected in parallel across the contacts, and the load 185. The voltage induced across the winding 164 due to the change in magnetization of the core 162 produces a current pulse through the main winding 175, the auxiliary winding 176 and the rectifier 168. The strengthened lines of force through the poles 174 and 173 of the electromagnetic switch 172 close the contacts by attracting the prismatic armature 178. The lines of force produced by the induced voltage across the taps 165 and 166 of the coil 164 are prolonged'by the discharge of capacitor 171. l

The capacitor 171 is connected in parallel across the coils 175 and 176 and is charged with the voltage induced across the taps 165 and 166.

A secondary winding 167 is wound on, the core 162 d having an air gap 163, and its function will be hereinafter described.

As the current from the alternating current source 161 continues to rise after the step, the lines of force due to the main winding are strengthened, causing the pressure on the contacts to be increased. When the current decreases to a relatively Zero value a voltage is induced in the coils 16d and 167 due to the reverse magnetization of the core 162. The voltage induced across the taps and 166 causes no current flow due to the blocking effect of the rectifier 168. The voltage, however, across the coil 167 causes a current flow through the rectifier 169 to the opening coil 183. The opening coil 183 is wound on the pole 1811 which in conjunction with the pole 181 forms the sides of the opening magnet 179. The opening magnet 179 has, in addition, a permanent magnet 182 aiding the efiect of the opening coil 183.

The magnet 182 does not have sufiicient strength to cause the opening of the contacts by moving the prismatic armature 173. When, however, the permanent magnet 182 is aided by the action of the voltage across the coil 183 the armature 178 is moved to the open position. The combined effect then of the permanent magnet 112 and the decreasing current step in the saturable core 162 cause the armature 178 to be attracted to the switching-oh? position and lifted from the poles 173 and 174.

Upon the cessation of the secondary voltage across the coil 167, which is essentially the cessation of the step, the armature 17% remains in the switched off position due to the sufficient attraction of the permanent magnet 182. The magnet 1%2 then has sufficient strength to maintain it in position once it is moved.

When the current from the alternating current source 161 is reversed to rise again the operation in the circuit proceeds as described above, with the addition that a current pulse from the winding 167 flows through the variable resistor 170, bridging the rectifier 169.

The current flows through the switch-oil coil 183 in the reverse direction, thus weakening the attracting force of the permanent magnet 132. This sharp decrease in the attracting force causes the armature 178 to fall into the contact position even without the attractive action of the magnetic switch 172.

The acceleration of the movement of the armature 178 is caused in the switching-on period by the effect of the winding 176 and in the switching-off period by the effect of the winding 183.

The permanent magnet 182 only secures the armature 178 in the off position in the absence of the current in the coil 183.

In the modification of the present invention as shown in Figure 4 a circuit is designed especially for high current values. The main current path from the alternating current source is through the line and the bars 2105 and 2% bridged by the armature 207, thence to the load 213 and back again to the alternating current source 190. The change of magnetization in the saturable core 191 is produced by the current carried through the conductor 195, or in other words, the core 191 and associated windings is built in the form of a starting current transformer.

The magnetic switch 2119 has the poles 2191 and 202 situated on each side of the armature 207. Essentially, the magnetic switch 200 is similar to the magnetic switches described in reference to Figure 5, with the addition of a second permanent magnet 21 3, the function of which is hereinafter described.

The operation of the equipment as shown in Figure 4 is essentially the same as the operation of the circuit as described in Figure 3. The addition of the permanent magnet 2113 assures the closed position of the armature 207 until the current passes through zero at the switch .ing-ofi period. During the opening contact period a pulse is initiated by the winding 192 on the core 191 which flows through the resistor 198, by-passing the rectifier 196 to the auxiliary win-ding 204 on the pole 2012, described above. The efiect of the pulse in the auxiliary winding quickly offsets the holding action of the permanent magnet 203 and releases the armature 207.

When a rising current is initiated by the alternating current source 190 a pulse appears on the windings 192 and 193 of the core 191 which is premagnetized from the direct current source 215 through the coils 194 and 214. The pulse on the winding 192 causes a closing of the contacts through energization of the coil 204 and the pulse on the winding 193 offsets the efiect of the holding permanent magnet 210. The pulse from the coil 193 flows through the rectifier 197 by-passed by a resistor 199 to the opening coil 211. The coil 211 is wound on the pole 209 which together with the pole 203 essentially forms the opening magnet. The pulse through the coil 211 offsets the holding action of the permanent magnet 210 allowing the armature to fall to its closed position.

The current from the alternating current source flowing through the line 195 and rectifier 212 is shorted through the bar 205, the armature 207 and the bar 206.

The current transformer arrangement as shown in Figure 4 may be used without the additional switch-off arrangement. The opening of the contacts may be achieved in a manner similar to that described in Figures 1 and 2.

When the electromagnetic switch systems of the present invention are utilized in applications that require a very rapid switching system of times of or less seconds it is applicable to use the relay coil for the saturated choke coil as shown in Figures 3 through 6. When, however, the switching time is to be longer, at 3X10- seconds for example, then the switching-on step is generally too long,

resulting in a high inductive voltage drop. In such a case an additional saturated choke coil may be used having a shorter intermediate step time.

In the foregoing I have described my invention solely in connection with specific embodiments thereof. Since many variations and modifications of my invention will now be obvious to those skilled in the art, I prefer to be bound not by the specific disclosures herein contained but only by the appended claims.

I claim:

1. An electromagnetic converter for providing a unidirectional current from an alternating current source to a load comprising a commutating reactor and an electromagnetic switch; said commutating reactor comprising a main winding wound on a magnetic core which saturates at relatively low values of current; said electromagnetic switch comprising a magnetic core, a closing winding, a holding winding, said closing winding and said holding winding being wound on said electromagnetic switch magnetic core; contact means including an armature mounted with respect to said magnetic core; said armature being movable to efi'ect contact engagement and disengagement; a rectified connected in parallel with said contact means; said main winding of said commutating reactor connected directly in series with said holding winding of said electromagnetic switch, said parallel combination of said contact means and said rectifier, said load and said alternating current source to form a load circuit for said electromagnetic converter; a gas filled tube having a plate, grid, and cathode; a direct current source to provide plate potential to said gas filled tube; a capacitor; said plate or" said gas filled tube connected through said capacitor to one end of said closing winding; said plate, cathode, capacitor and closing winding forming a closed series connection; said grid of said gas filled tube connected to a center tap of said commutating reactor main winding; said cathode of said gas filled tube connected to one end of said commutating reactor main winding; said main winding providing a positive potential on the grid of said gas filled tube when said commutating reactor is unsaturated immediately prior to the movement of said armature to engaged position; said positive grid potential and said plate potential of said gas filled tube from said direct current source resulting in the firing of said gas filled tube to thereby cause a current pulse to flow through said clos- Eng winding.

2. An electromagnetic rectifier for providing a unidirectional current from an alternating current source to a load comprising a commutating reactor and an electromagnetic switch; said commutating reactor comprising a main winding wound on a magnetic core which saturates at relatively low values of current; said electromagnetic switch comprising a magnetic core, a closing winding, a holding Winding, said closing winding and said holding winding being wound on said electromagnetic switch core; contact means including an armature mounted with respect to said magnetic core; said armature being movable to effect contact engagement and disengagement; a bypass circuit means including unidirectional current conducting means being connected in parallel with said contact means; a gaseous triode comprising an emitter, a receiver, and a control element; said control element electrically connected to a tap on said main winding; a capacitor and means for charging said capacitor; said emitter, receiver, capacitor and closing winding forming a closed series connection; said emitter of said gaseous triode connected to one end of said main Winding; said alternating current source and said load connected in series with said main winding, said holding winding, and said contact means of said electromagnetic switch to thereby form a load circuit for said electromagnetic rectifier; said commutating reactor supplying a pulse to said control element of said gaseous triode prior to the movement to engaged position of said armature; said pulse causing the firing of said gaseous triode to thereby energize the closing winding of said electromagnetic switch.

References Cited in the file of this patent UNlTED STATES PATENTS 1,265,354 Mershon May 7, 1918 2,094,361 Lee Sept. 28, 1937 2,293,296 Jonas Aug. 18, 1942 2,465,682 Goldstein 1. Mar. 29, 1949 2,502,932 Diebold Apr. 4, 1950 FOREIGN PATENTS 905,953 France Dec. 19, 1945 613,540 Great Britain Nov. 30, 1948 113,439 Sweden Mar. 13, 1945

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