Introduction• Liquid metal are conductors.• Based on the Fleming’s Left Hand Rule.• Current flowing vertically through the liquid metal experiences a force (F = I L x B)along the tube as shown.
Types of EM Pumps• Conduction pump - current is directly conducted into the fluid throughelectrodes. Two variants, A.C & D.C.• Induction pump - current in the conducting fluid is induced by a travelingmagnetic field.• Thermoelectric pump - current flowing through the liquid metal is deriveddirectly from the thermal power contained in the hot liquid-metal flow.D.C conduction pumpInduction pump Thermoelectric pump
ApplicationsTwo main applications:• Cooling of nuclear reactor.• Pouring and transportation of high temperature metals in foundry.Image of EM pump used in nuclear reactor Assembled EM pump for foundry(Courtesy CMI Novacast Inc.)(Courtesy Handbook of Nuclear Engineering byDaniel Gabriel.)
EM Pump from InsideThe electrical current is induced by transformeraction. The transformers primary coil T in Figureis connected to an AC single-phase powersource. The transformer pole pieces arearranged in the shape of a picture frame andserve as the carrier of magnetic flux. Thetransformer secondary winding S around thebottom leg of the picture frame is molten metaland is formed by channels in ceramic parts. Theshape forms a single turn shorted winding. Theturns ratio amplifies the electrical input currentto produce very high amperage I in the moltenmetal.Courtesy CMI Novacast Inc.
EM Pump from Inside (continued)A sectioned view of the electromagnetconstruction is added, which consists of a C-shaped pole piece and two excitation coils. Theopening in the C straddles the necked-downsection of the molten secondary turn, so themagnetic field H crossing the pole gap isperpendicular to the secondary current I,resulting in force Q to move metal through thepump.Courtesy CMI Novacast Inc.
EM Pump from Inside (continued)This is the complete pump. It is surrounded by orencapsulated in ceramic parts to protect it frommolten metal contact. Pump output Q is variedby controlling input power and can be regulatedfrom almost drop-wise flow up to full boredelivery.Courtesy CMI Novacast Inc.Low pressureside fill
Advantages & LimitationsAdvantages:• No moving parts, no vibrations or wear and tear.• No seals, no spills.• Less maintenance and more reliable.Limitations:• Power losses due to back EMF, Ohmic heating.• Limited uses since very few liquids are good conductors of electricity.