Reducing current reversal time in electric motor control

• US 8,878,473 B2
• Filed: 06/02/2011
• Issued: 11/04/2014
• Est. Priority Date: 06/02/2011
• Status: Active Grant

• Current Assignee: National Technology & Engineering Solutions Of Sandia LLC (Honeywell International Inc.)
• Original Assignee: Sandia Corporation (Martin Marietta Corporation)
• Inventors: Bredemann, Michael V.
• Primary Examiner(s): DUDA, RINA I
• Application Number:
  US13/152,067
• Publication Number:
  US 20140103845A1
• Time in Patent Office: 1,251 Days
• Field of Search: 318/400.21, 318/400.22, 318/400.26, 318/400.29
• US Class Current: 318/400.21
• CPC Class Codes: H02P 6/15 Controlling commutation time

Abstract

The time required to reverse current flow in an electric motor is reduced by exploiting inductive current that persists in the motor when power is temporarily removed. Energy associated with this inductive current is used to initiate reverse current flow in the motor.

Claims

1. An apparatus for controlling current in a winding of an electric motor, the apparatus comprising:

a current switching structure including first and second nodes adapted for coupling the winding in series therebetween, a pair of power supply nodes configured to provide power supply current to an electric motor winding being driven by said current switching structure, and a current blocking device coupled between one of said first and second nodes and one of said power supply nodes, the current blocking device configured to ensure that freewheeling inductive current at the first and second nodes is not clamped to one of said power supply nodes;

a controller coupled to said current switching structure and configured to control said current switching structure when the winding is coupled between said first and second nodes, said controller configured for controlling said current switching structure to assume a first configuration that permits power supply current flow in a first direction from said first node through the winding to said second node, and for thereafter controlling said current switching structure to execute a first transition from said first configuration to a second configuration that permits power supply current flow in a second direction from said second node through the winding to said first node; and

an energy storage device coupled to said one of said first and second nodes and cooperable with an inductive current that persists in said first direction through the winding during a first interval of said first transition for one of storing energy and releasing energy during said first interval, said current blocking device blocking said inductive current from said one power supply node during said first interval, said energy storage device operable, during said first transition and after said first interval, for the other of storing and releasing energy to permit a further current flow in said second direction from said second node through the winding to said first node.

2. The apparatus of claim 1, wherein said controller is further configured for controlling said current switching structure to execute a second transition from said second configuration back to said first configuration, wherein said current switching structure includes a further current blocking device coupled between the other of said first and second nodes and the other of said power supply nodes, and wherein said apparatus includes a further energy storage device coupled to said other of said first and second nodes and cooperable with another inductive current that persists in said second direction through the winding during a second interval of said second transition for one of storing energy and releasing energy during said second interval, said further current blocking device blocking said another inductive current from said other power supply node during said second interval, said further energy storage device operable, during said second transition and after said second interval, for the other of storing energy and releasing energy to permit a further current flow in said first direction from said first node through the winding to said second node.

3. The apparatus of claim 2, wherein each said energy storage device includes a capacitor, and each said current blocking device includes one of a diode, a silicon-controlled rectifier, a bipolar junction transistor, and a field effect transistor.

4. The apparatus of claim 1, wherein said energy storage device includes a capacitor, said storing energy includes charging of said capacitor, and said releasing energy includes discharging of said capacitor.

5. The apparatus of claim 4, wherein said controller is configured to control said first transition such that said current switching structure assumes said second configuration before a voltage across said capacitor reaches a predetermined level.

6. The apparatus of claim 1, wherein said controller is configured to control said current switching structure to assume, during said first transition, first and second intermediate configurations that differ from one another and from said first and second configurations.

7. An apparatus for controlling current in an electric motor having a winding structure including a plurality of windings, the apparatus comprising:

a current switching structure including a first node adapted for coupling to the winding structure, a pair of power supply nodes configured to provide power supply current to an electric motor winding being driven by said current switching structure, and a current blocking device coupled between said first node and one of said power supply nodes, the current blocking device configured to ensure that freewheeling inductive current at the first node is not clamped to one of said power supply nodes;

a controller coupled to said current switching structure and configured to control said current switching structure when the winding structure is coupled to said first node, said controller configured for controlling said current switching structure to assume a first configuration that permits power supply current flow in a first direction between said first node and the winding structure, and for thereafter controlling said current switching structure to execute a first transition from said first configuration to a second configuration that permits power supply current flow in a second direction between said first node and the winding structure, wherein said second direction is opposite said first direction; and

an energy storage device coupled to said first node and cooperable with an inductive current that persists in said first direction between said first node and the winding structure during a first interval of said first transition for one of storing energy and releasing energy during said first interval, said current blocking device blocking said inductive current from said one power supply node during said first interval, said energy storage device further operable, during said first transition and after said first interval, for the other of storing and releasing energy to permit a further current flow in said second direction between said first node and the winding structure.

8. The apparatus of claim 7, wherein said energy storage device includes a capacitor that becomes one of fully charged and fully discharged during said first interval.

9. The apparatus of claim 7, wherein the motor winding structure is one of a Y-connected structure and a Δ

-connected structure.

10. The apparatus of claim 7, wherein said controller is further configured for controlling said current switching structure to execute a second transition from said second configuration back to said first configuration, wherein said current switching structure includes a further current blocking device coupled between said first node and the other of said power supply nodes, and wherein said energy storage device is cooperable with another inductive current that persists in said second direction between said first node and the winding structure during a second interval of said second transition for one of storing energy and releasing energy during said second interval, said further current blocking device blocking said another inductive current from said other power supply node during said second interval, said energy storage device operable, during said second transition and after said second interval, for the other of storing energy and releasing energy to permit a further current flow in said first direction between said first node and the winding structure.