Electromagnet control circuit
AssigneeSquare D Company
InventorJohn P. Cooper
Life of this patent
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Abstract
A circuit for controlling operation of an electromagnet includes a source of voltage connectable to the electromagnet to produce current flow in one direction and develop a magnetic force therein. A dissipating circuit is connectable to the electromagnet to form a closed loop and has impedance means for dissipating stored energy with gate means between the closed loop and the source producing current flow from the source through the closed loop when the residual potential drops to the potential of source and produce reverse current flow through the magnet. The circuit also has a reverse current limiting means in parallel with the impedance means and includes a manually variable resistor to adjust the limit of reverse current flow.
Claims12
Circuitry for controlling the operation of an electromagnet coupled to a source of voltage, said source having a predetermined potential for producing current flow through said electromagnet, said circuitry comprising a first circuit connectable to said source for producing current flow in one direction and develop a magnetic field in said electromagnet, a second circuit connectable to form a closed loop with said electromagnet and having impedance means for dissipating stored energy in said electromagnet, gate means between said source and said second circuit for connecting said source to said second circuit when the level of stored energy drops to the level of potential of said source to continue dissipation of stored energy, and to initiate a current flow in a relatively reverse direction through said magnet when the residual potential drops below a predetermined value, and a means of terminating the flow of reverse current after it has risen to a second predetermined value.
A circuit for controlling the operation of an electromagnet, comprising first and second conductors connected to a voltage source for producing current flow, a lifting circuit between said conductors having normally open contact means closeable to produce current flow in one direction through said magnet and develop potential in said electromagnet for a lifting operation, a second circuit connectable to said electromagnet to form a closed loop with said electromagnet to dissipate residual potential in said electromagnet when said contact means are opened with means for isolating said second circuit until the residual potential drops to the level of potential across said conductors, said second circuit including series connected fixed impedance means for dissipating said residual potential and for reversing current flow through said electromagnet and manually variable impedance means in parallel with at least one of said fixed impedance means, said manually variable impedance means defining the level of reverse potential through said electromagnet.
A method of controlling the operation of an electromagnet comprising the steps of connecting a source of voltage to said electromagnet to produce current flow in one direction and develop a potential therein, disconnecting said source from said electromagnet and connecting a dissipating circuit to said electromagnet to continue current flow in said one direction and reduce the residual potential and voltage in said electromagnet, connecting said source to said dissipating circuit when the potential of said source equals the potential of said dissipating circuit to maintain the voltage across said electromagnet at an elevated value and continue reduction of said residual potential, reversing the current flow through said magnet when the residual potential therein drops to a predetermined value, and disconnecting said source from said dissipating circuit and electromagnet when the current flow in the reverse direction reaches a predetermined value.
Dependencies are inferred from the claim text.