US2787219A - Alternating current electromotive liquid metal pump - Google Patents

Description

April 2, 17957 R. c. WERNER 2387219 ALTERNATING CURRENT sLEcTRoMoTIvE LIQUID METAL PUMP Filed Dec. 7, 1954 4 Sheets-Sheet 2 ROBERT CWERNER INVENTOR.

HIS A TORNEY April z, 1957 R. c. WERNER 2,787,219

ALTERNATING cuRRENT ELEcTRoMoTIvE LIQUID METAL PUMP Filed Dec. 7, 1954 4 snee'ts-shee: s

ROBERT C. WERNER INVENToR.

April 2, 1957 R. c. WERNER 2,787,219

ALTERNATING CURRENT ELECTROMOTIVE LIQUID METAL PUMP Filed Dec. 7, 1.954 4 Sheets-Sheet 4 -FLOW ROBERT -C.WERNER l IN V EN TOR.

BY HIS TORNEY ALTERNATING CURRENT ELECTROMOTIVE LIQUID METAL PUMP Robert C. Werner, Lancaster Township, Butler County,

Pa., assignor to Mine Safety Appliance Company, Pittsburgh, Pa., a corporation of Pennsylvania Application December 7, 1954, Serial No. 473,525

2 Claims. (Cl. 103-1) This invention relates to new and useful improvements in pumps for liquid metals and more particularly to a new and improved alternating current electromotive pump. This invention further relates to electromotive liquid metal pumps of the type in which the liquid metal is forced to flow through a conduit by the electromotive reaction between an electric current passing through the liquid metal perpendicular to the direction of flow of the liquid metal and intersecting a magnetic field extending perpendicular to both the electric current and the direction of flow of the liquid metal.

In recent years a need has developed for an electromagnetic pump capable of efiiciently moving an electrically conducting liquid metal such as sodium or an alloy of sodium and potassium. The advantage of pumps of this type resides in the fact that no moving parts are involved and also that the liquid metal which is moved by the pump can be confined in a closed system without requiring complicated packings, valves, and the like. The basic principle upon which the electromotive liquid metal pump is based was enunciated by Faraday more than 100 years ago. Since that time there have been numerous applications of this principle to the movement of liquid metals. Some of these applications have involved the movement of a column of mercury in a metering device or in measurement of pressure, while other applications have involved the mixing of molten metals in furnaces and the pumping of liquid metals to die casting machinery and the circulation of liquid metals for heat exchange purposes. The efficiency of electromotive liquid metal pumps has been so much less than that of conventional displacement type pumps that considerable eforts have been made to improve the pumping efficiency.

It is therefore one object of this invention to provide a new and improved alternating current type electromotive liquid metal pump of increased efIiciency and more compact design. p

Another object of this invention is to provide a new and improved electromotive liquid metal pump which is constructed in a manner to reduce substantally the external electric losses in the pump.

Another object of this invention is to provide a new and improved electromotive liquid metal pump in which the electromotive force is applied to the liquid metal at two separate points along the conduit and thus producing an increased pumping efliciency.

Other objects will become apparent from time to time throughout the specification and claims as herenafter related.

This invention comprises the new and improved construction and combination of parts, which will be described more fully herenafter and the novelty of which will be particularly pointed out and distinctly claimed.

In the accompanying drawings, to be taken as part of this specification, there is clearly and fully illustrated a preferred embodiment of this invention, in which drawings,

`fited tates Patent F ,787,2l9 Patented Apr. 2, 1957 Figure 1 is a Perspective view or isometric projection of this new and improved electromotive pump,

Figure 2 is a sectional view taken on a vertical plane extending through the line 2-2 of Fig. 1,

Figure 3 is a view in longitudinal section taken on a Vertical plane extending through the line 3-3 of Fig. l, and

Figure 4 is a horizontal section taken on a horizontal plane extending through the line 4-4 of Fig. 1.

Referring to the drawngs by numerals of reference and more particularly to Fig. 1 there is shown a pump assembly 1. The pump 1 includes a hollow conduit 2 which is shown `as a square or rectangular shaped conduit but which could be if desred a conduit of circular cross section having a portion of square or rectangular cross section. For elficient operation of this pump the conduit 2 must be of a non-magnetic material such as copper, a copper alloy, or stainless steel. Secured to the conduit 2 and extending from opposite sides thereof in the horizontal plane are a pair of laminated copper conductors or bus bars 3 and 4 respectively. The copper bus bars 3 and 4 are preferably welded or brazed to the conduit 2 at the front and rear pumping sections 5 and 6 respectively. The bus bars 3 and 4 form the secondary loops for a pair of current transformers 7 and 8 respectively and are connected in series. The current transformers 7 and 8 each have laminated iron magnetic cores 9 and 10 and are provided with primary coil windings 11 and 12 respectively. The primary coils 11 and 12 of the current transformers 7 and 8 are connected so that the current in the secondary circuit circulates through the bus bars 3 and 4 and crosses the pumping section 5 and 6 by passing through the liquid metal which is being circulated through the conduit 2.

The pump is also provided with a magnetic circuit which comprises a pair of laminated iron magnetic cores 13 and 14 which lie in a Vertical plane relative to the plane of the current transformer secondary coils 3 and 4. The magnetic cores are of a laminated construction and form horeshoe shaped magnets which are secured to the conduit 2 on opposite sides thereof at the front and rear pumping sections 5 and 6 respectively. The magnetic cores 13 and 14 are energizable to produce a magnetic flux crossing the pumping Sections 5 and 6 respectively (as shown in Fig. 3) perpendicular to the direction of flow of the electric current in the `transformer secondary circuit. The upper magnetic core 13 is provided with a pair of magnetic field coils 15 and 16 respectively. The lower magnetic core is provided with a similar pair of field coils 17 and 18 respectively. The magnetic field coils 15, 16, 17 and 18 are connected in an electric circuit such that when energized the flow of magnetic fiux through the magnetic cores 13 and 14 and across the pumping Sections 5 and 6 will be in series as a con-tinuous loop.

Operation In operation this pump functions according to the left hand rule of physics which determines the direction of thrust of an electric motor. In this pump an electric current is impressed across a conductor (the liquid metal in the conduit 2) perpendicular to a magnetic field which also cuts across the conductor. The intersection of the electric current and the magnetic field causes the conductor to move in the direction indicated by the left hand rule. In this pump the liquid metal in the conduit 2 is the conductor and therefore moves as if it were the rotor of an electric motor. When the current transformer coils 11 and 12, and the magnetic field coils 15, 16, 17 and 18 are energized an alternating current will circulate through the secondary conductors 3 and 4 and a continually reversing magnetic field will circulate through the magnetic cores 13 and 14. When the current transformers are being energized the electric current will alternate back and forth in a complete circuit through the conductors 3 and 4 and cross the pumping sections and 6 as indicated in Fig. 4. At a given instant the current in the conductors 3 and 4 will be moving in the direction indicated by the arrow on the conductor 4 in Fig. 1. Onehalf cycle later the current will be flowing in the opposite direction. The magnetic circuit which consists of the magnetic cores 13 and 14 and the energizing coils therefor is operable to produce a magnetic field which circulates through the magnetic cores 13 and 14 and across the pumping seetions 5 and 6 as indicated in Fig. 3. At the same instant that the electric current is moving in the direction indicated by the arrow on conductor 4 in Fig. l the magnetic flux in the magnetic circuit is circulating in the direction indicated by the directional arrow on the magnetic core member 13 in Fig. 1. The force which is produced by the intersection of the magnetic field and the electric current in the pumping Sections 5 and 6 will cause the liquid metal in the conduit 2 to move in the direction of fiow indicated by the directional arrow adjacent the conduit 2 in Fig. 1. When the current flowing through the transformer secondary conductors 3 and 4 is flowing in the opposite direction from that indicated by the directional arrow in Fig. 1 the change in current in the magnet field coils will have caused the magnetic flux to reverse its direction and flow in a direction opposite to the directional arrow on the magnetic core member 13 in Fig. 1. When the current and the magnetic field are both reversed in direction the electromotive thrust on the liquid metal in the conduit 2 remains in the same direction as indicated by the directional arrow. This arrangement of the magnetic circuit and the intersecting electrical circuit causes an electromotive thrust to be applied to the liquid metal in the conduit 2 as a series of impulses having a frequency equal to two times the frequency of the alternating current used to energize the transformer and magnetic field coils.

In this pump there are several distinct advantages which arise from the arrangement which is used to produce a pumping impulse at two spaced points along the conduit 2. In this pump construction the arrangement of two current transformers balanced in output and having their secondary conductors 3 and 4 connected additively across two separate pumping sections 5 and 6 results in a larger current flow across the liquid metal in the conduit 2 at each of the pumping Sections 5 and 6 and reduces the electrical losses due to shorting of the electric current through the liquid metal. In a similar manner the arrangement of two magnetic armatures above and below the conduit 2 which produce a magnetic circuit having a larger quantity of magnetic flux passing directly across the pumping Sections 5 and 6 and more nearly at right angles to the electric current crossing those pumping Sections results in more efficient operation of the pump. In this pump construction use is made of the electric current and magnetic flux at two separate points in the electric and magnetic circuit thus making a more efiicient use of the electrical energy applied to the pump. It should also be noted in connection with this type of pump that the reversal of electrical connections for either the magnetic field coils or the primary coils of the current transformers will result in a reversal of the direction of flow of the electric current in the transformer secondary conductors 3 and 4 relative to the flow of the magnetic flux in the magnetic cores 13 and 14 and thus will result in a reversal of flow of the liquid metal in the conduit 2. This reversal of flow can be accomplished therefore by a reversing switch in the circuit of either the magnetic field coil or the current transformers.

Altthough there has been described herein only one embodiment of this invention it will be obvious to those skilled in the art that other embodiments of this invention are possible without departing from the scope and intent of coverage thereof and that within the scope of the claims appended hereto this invention may be practiced otherwise than as specifically described.

Having thus described my invention and the manner in which it is to be performed what I desire to claim and secure by Letters Patent of the United States is:

1. In an electromotive liquid metal pump a conduit for a liquid metal, a pair of current transformers having secondary windings electrically connected to said conduit at two points spaced along said conduit, said secondary windings being connected in series across said conduit at said spaced points to produce a single electric circuit passing perpendicularly through said conduit and the liquid metal therein, whereby there is substantially no short circuiting of said secondary windings lengthwise of the conduit through the liquid metal between said points, magnetic circuit means connected to said conduit to produce a single magnetic circuit having magnetic fiux passing perpendicularly through said conduit and the liquid metal therein and intersecting the electric current perpendicularly thereto at said spaced points on said conduit, and said magnetic fiux and electric current intersecting said spaced points on said conduit to apply separate electromotive impulses to the liquid metal therein.

2. In an electromotive liquid metal pump, a conduit of non-magnetic material for conducting a liquid metal, a pair of current transformers positioned adjacent said conduit, said transformers each having a U-shaped laminated bus bar as the secondary winding thereof lying in a plane and having the open ends aligned and secured to opposite sides of said conduit, said transformers each having a laminated iron core and a primary winding therefor, said primary windings being connected to energize said secondary windings in series and thus to transmit an electric current across said conduit and the liquid metal therein at two spaced points along said conduit, the potential difference through the liquid metal between said two points being substantially zero, a pair of laminated iron magnetic core members secured to opposite sides of said conduit and extending in a plane peipendicular to the plane of said secondary windings, said core members being U-shaped and having their open ends aligned with the ends of said secondary windings, field coils surrounding said magnetic core members and connected to produce a series magnetic flux circuit upon energization, and said field coils and said current transformers being operable upon energization With alternating current of the same frequency to impress an alternating current and an alternating magnetic field across said two spaced points on said conduit and thereby applying an electromotive thrust at said two points at a frequency equal to two times the frequency of the alternating current.

References Cited in the file of this patent UNITED STATES PATENTS 1,792,449 Spencer Feb. 10, 1931 2,386,369 Thompson Oct. 9, 1945 2,612,l09 Wakefield Sept. 30, 1952 2,686,474 Pulley Aug. 17, 1954

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