US2260810A - Control system - Google Patents

Description

CONTROL SYSTEM Filed March '7, 1940 Inventor"; Ber'Jarnir-i W. Jones,

His ttorneg Patented Oct. 28, 1941 CONTROL SYSTEM Benjamin W. Jones, Schenectady, N. Y., assiznor to General Electric Company, a corporation of New York 7 Application March 7, 1940, Serial No. 322,786

Claims. (01. 175-475) My invention relates to control systems, more particularly to systems for operating electromagnetic switches and has for its object a simple and reliable system of this character.

In carrying out my invention, I provide a magnetic iron core for the operating coil of the main load switch which core is made of a material having relatively high m-agnetic flux retentivity whereby it retains a relativelygreat amount of residual magnetism'aiter the energizing coil is deenergized, this residual magnetic eiiect being great enough to hold the switch closed.

For the control of the energizing winding of the main switch, I provide a two-way single pole control switch which, when thrown in one direction, connects the coil for energiza'tion in parallel with the main switch and in series with the load whereby the coil is short circuited when the main switch is closed, and the main switch is held closed by the residual magnetism of the core. To open the main switch, the control switch is thrown to its other position whereby the coil is connected for energization through the main switch and in parallel with the load and is deenergized when the switch opens.

For a-more complete understanding of my shown, by means of a helical spring 25.

invention, reference-should be had to the ac- A companying drawing, Fig. 1 of which is adiagrammatic representation of a control system embodying my invention; while Fig. 2 is an elevation view of a preferred form of switch.

I have shown my invention in one form as applied to the opening and closing of a main switch Hi to control a load circuit H energizing,

as shown, a plurality of electric lamps 12. The

- switch 18 is normally biased to its open circuit position as by a spring or, as shown in Fig. 1, by gravity. It is moved to its closed position by means of a suitable coil l3. When closed, the switch it connects the lamps l2 across suitable supply mains II and I5 which may be energized either with alternating or direct current.

The coil I3 is provided with a magnet iron core l8 having sufdcient magnetic retentivity to hold its armature in its attracted position and thereby hold the switch i0 closed for an indefinite period 0! time after the'coil II has been deenergized. I

For example, the core may be made of a-materlal containing three (3) per cent or-more o'i chromium by weight, the remainder being iron.

For the purpose of the-coil I8 is connected to the point I! which is between the switch I I and the load, shown as electric lamps l2. The other end of the coil is connected to a two-way single pole control switch l8. When this switch is thrown toward the left hand, as seen in the drawing, it connects the coil [3 across or in parallel with the open switch l0 so that the coil i3 is thereby connected across the mains l4 and IS in series with the load 12. The coil l3 thereupon closes the switch It! and the switch in closing short circuits the coil I3, the switch being held closed by the residual ma netism in the core of the coil 13.

For the purpose of opening the main switch ID, the switch arm I8 is thrown to its right hand position whichconnects the coil l3 in series with s. suitable resistance IS in parallel with the lamps switch Hi to open. When the switch Ill opens,

the coil I3. is deenergized for the reason that it is connected in series withthe switch I0.

In the preferred form of electromagnetic switch l0 shown in Fig. 2, the pivotally mounted armatiire 20 is biased to the open circuit position The armature 20 and the stationary core member 22 are made of a suitable material, mainly iron, which retains a suflicient amount of residual magnetism to hold the armature, in its attracted position after the coil 23 has been energized to pick up the armature 20 and then deenergized. This is a desirable means of holding the switch closed for an indefinite period against the force applied by the spring 2!. It requires no additional energy and has no resultant noise.

Because of the fact that the armature 20 is released by neutralizing the residual magnetism in the; magnetic structure of which it forms a part, instead of having a low value of residual magnetism insufllcient, to retain the armature when the circuit of the coil is opened, no air gap is provided between the armature and the core member 22. Moreover, the absence of the air gap gives the residual magnetism an advantage in holding the armature in its attracted position.

In order to provide for wear of the engaging contact surfaces of the switch I0, the movable contact of the switch which is operated by the armature is resiliently secured to the armature so that the switch 10 is closed before the arms.-

energizing it, one side of ,ture has reached its final sealed in or attracted position. By reason of the short circuiting of the coil is or 23 by the closure of the switch, however, the coil maintains the magnetic fiux in the core structure a high value for a substantial period of time y Qason of the seli inductance of the coil. This maintenance of the flux by the short circuited coil is sufilcient in time to provide for the armature to be pulled to its final attracted position. The magnetic flux thereupon decreases to its residual value.

For example, in the arrangementof Fig. l, the movable contact 21, shown as a bridging contact, is slidably mounted on the rod 2'5 connected to the movable armature 2B. The contact is resiliently pressed against a stop on the end of the rod 25 by means of a helical spring 21 surroundmg the rod. Thus, after the movable contact engages the stationary contacts and the switch is closed, the spring 27 is compressed by continued movement of the armature 26 to its attracted position. In the arrangement of Fig. 2, the contact arm 28 carrying the movable contact can be flexible to provide a similar eflfect.

It w ll be understood that the control switch 18 ma be operated in any suitable manner. For example, it may be operated as a limit switch or it may be operated in response to variable quanti ties such as light, temperature, pressure, liquid level, etc. also load i2, indicated as electric lamps, may be any suitable load such as an electric motor. The switch 18, of course, may also be operated manually, as shown in Fig. l, for example, in the turning on and off of street lamps, indicated by the lamps l2.

It will be observed that when the control switch 55 is closed, it is immediately thereafter either short circuited by the switch I!) or its circuit is opened by the switch 10 so that the switch it? is thereafter opened with ,no voltage across its contacts.

In view of the fact that the coil 13 is energized only momentarily, it can be of inexpensive construction and be wound with a relatively small copper conductor which would m overheated if continuously energized from the supply circuit.

When operating with alternating current on the supply main l4 and I5, if the switch l should close at about the zero point on the current wave, the residual magnetism may not be strong enough to hold the switch closed. In such case, the switch 58 opens and its coil 13 is immediately reenergized whereupon the switch closes again. Qbviously the switch cannot be noisy when operating on A. C. except for the momentary periods when the coil is connected to the supply mains.

when the supply mains l4 and 36 are supplied with dir ct current, it will be observed that the control switch l8 when thrown to its right-hand position reversely energizes the coil 23 and consequently the residual magnetism is neutralized. The resistance 59 allows the correct amount of current to demagnetize the core, i. e. reduce its residual magnetism to a low value insumcient to hold the armature in its attracted posit r.

When the supply mains are energized 'ith alternating current, I have found that ener izetion of the coil l3 at a low value through an impedance, as shown the resistance l9, very effectively reduces after a few cycles of the current the residual magnetism in the core to a low value insufficient to hold the armature in itsattracted position against its bias to its unattracted position. The armature then moves to its unattracted position opening the switch it. In'iact, the switch Ill opens practically instantaneously after the closing of the control switch I8 to demagnetize the coil.

It will be understood that when alternating current is used to demagnetize the core, the demagnetizing current must be smaller than the current required to pick up the armature or to hold the armature in its attracted position. In other words, the alternating current must beso weal: that the out-of-phase flux produced by the shading coil on the core is too small to hold the armature in its attracted position. One half of each. current wave of the demagnetizing current produces a flux in the core in opposition to the residual magnetism in the core while the other half of the wave tends to remagnetize the core. However, the residual magnetism is reduced each cycle more than it is built up because of the fact that more energy is required to magnetize a core than to demagnetive it. As a result, the core is dernagnetlzed by successive cycles of the demagnetizing current.

Preferably the resistance I9 is one having a positive temperature coefliclent of resistance when A. C. power is used and is selected so that it heats after a few cycles of current to a temperature at which its resistance is 8 or 20 times its cold resistance value. A suitable tungsten lamp is a very satisfactory resistance of this type. This increasing resistance by reducing the current approaches the effect obtained by gradually reducing the voltage on the coil. This effectively reduces the residual magnetism in the core to a low value insufiicient to hold the armature in its attracted position.

While I have shown a particular embodiment of my inventiomit will be understood, of course, that I do not wish to be limited thereto, since many modifications may be made and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope or my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a switch biased to its open circuit position, a cell for operating said switch to its closed circuit position, a magnet iron core structure for said coil having sufficient residual magnetism after said coil is deenerglzed to hold said switch closed, and a control switch movable to connect said coil across said switch for energization of said coil to close said switch whereby said coil is short clrcuited by said switch.

2. In combination, a switch biased to its open circuit position, a coil for operating said switch to its closed circuit position, a magnet iron core structure f\ r said coil having sufflcient residual magnetism after said coil is deenergized to hold said switch closed, and a control switch movable to one of two positions to connect said coil across said switch for energization of said coil to close said switch whereupon said coil is short circuited by said switch, said control switch being movable to its other position to connect said'coil in series with said switch for demagnetization of said core and opening 01' said switch.

3. In combination, a switch biased to its open circuit position, a coil for operating said switch to its closed circuit position, a magnet iron core structure for said coil having suflicient residual magnetism after said coil is deenergized to hold said switch closed, an impedance, and a control switch movable to one of two positions to cont nect said coll across said switch for energlzation of said coil to close said switch whereupon said coil is short clrcuited by said switch, said control switch being movable to its other position to connect said coil in series with said switch and said impedance for demagnetization of said core and opening 01' said switch.

4. The combination with an electric translatlg device, of a switch biased to its open posion in circuit with said device, a coil for oprating said switch to its closed circuit position, mnections for energizing said coil in series with iid translating device in parallel with said witch to close saidswitch whereby said transiting device is energized and said coil is short lrcuited, a magnet iron core structure for said oil having sufiicient residual magnetism after aid coil is deenergized to hold said switch closed, vnd connections for energizing said coil in par- .llel with said translating device to demagnetize aid core whereupon said switch opens in accordince with its bias and opens the circuits of said translating device and said coil.

5. The combination with an electric translatng device, of a switch biased to its open posi- 2101')- in circuit with said device, a coil for operating said switch to its closed circuit position, :onnections for energizing said coil in series with said translating device and in parallel with said switch to close said switch whereby said translating device is energized and said coil is short circuited, a magnet iron core structurefor said coil having suflicient residual magnetism after said coil is deenergized to hold said switch closed, an impedance, and connections for energizing said coil in parallel with said translating device through said impedance to demagnetize said core whereupon said switch opens in accordance'with.

its bias and opens the circuits of said translating device and said coil.

6. The combination with a switch, of a mag-' net core structure, a movable armature for said core structure, a spring connection between said armature and said switch providing for closure of said switch before said armature has reached its attracted position after which said spring yields to provide for movement of said armature to its attracted position, means biasing said armature to its unattracted position thereby to bias said switch to its open position, a coil on said core structur for operating said armature to move said switch to its closed circuit position, electrical connections for energizing said coil in parallel with said switch to close said switch whereby said coil is short circuited by said switch, said short circuited coil maintaining a high value of flux in said core structure for comof flux in said core structure for completion of the movement of said armature to its attracted position and said core structure having suflicient said impedance to demagnetize said core pletion of the movement of said armature to its attracted position and said ing sufllcient residual magnetism thereafter to hold said armature in its attracted position.

'7. The combination with a switch, of a magnet core structure, a movable armature for said core structure, a spring connection between said armature and said switch providing for closure of said switch before said armature has reached its attracted position after which said spring yields to provide for movement of said armature to its attracted position, means biasing said armature to its unattracted position thereby to bias said switch to its open position, a coil on said core structure for operatingsaid armature to move said switch to its closed circuit position, electrical connections for energizing said coil in parallel with said switch to close said switch whereby said coil is short circuited by said switch, said short circuited coil maintaining a high value core structure havresidual magnetism thereafter to hold said armature in its attracted position, an impedance, and connections energizing said coil through said impedance to demagnetize said core whereupon said armature moves to its unattracted position in accordance with its bias and opens said switch.

8. The combination with an electric translating device of a switch connected in circuit with said device, a magnet core structure, a movable armature for said core structure, a spring connection between said armature and said switch providing for closure of said switch before said armature has reached its attracted position after which said spring is compressed to provide for movement of said armature to its attracted position, means biasing said armature to its unattracted position thereby to bias said switch to its-open position, a coil on said core structure for operating said armature to move said switch to its closed circuit position, electrical connections for energizing said coil in series with said translating device and in parallel with said switch to close said switch whereby said translating device is energized and said coil is short circuited by said switch, [said short circuited coil maintaining a high value of flux in said core structure for completion of the, movement of said armature to its attracted position and said core structure having sufficient residual magnetism thereafter to hold said armature in its attracted position, an impedance, and connections for energizing said coil in parallel with said translating device through upon said armature moves to its unattracted position in accordance with its bias and opens the circuit of said translating device and said coil.

9. The combination with an electric translating device of a switch biased to an open circuit position in circuit with said device, a coil for operating said switch to a closed circuit position, connections for energizing said coil to close said switch and energize said translating device, means responsive to the closure .of said switch for deenergizing said coil, a magnetic core. structure for said coil having sufflcient magnetic retentivity to hold said switch closed ergized, and connections for energizing said coil in parallel with said translating device so as to cause said core structure to release said switch.

10. The combination with an electric-translating device of a switch biased to an open circuit position in circuit with said device, a coil for operating said switch to a connections for energizing said coil to close said switch and energize said translating device, means responsive to the closure of said switch for desaid core structure to release said switch wherein accordance with its upon said switch opens device and said bias to deenergize said translating coil.

BENJAMIN W. JONES.

after said coil is deen-' closed circuit position,

Images