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Three level pulse width modulated inverter for an electric vehicle

  • US 5,517,401 A
  • Filed: 12/12/1994
  • Issued: 05/14/1996
  • Est. Priority Date: 02/07/1992
  • Status: Expired due to Fees
First Claim
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1. An inverter for an electric vehicle which converts a DC voltage supplied from a main battery having a voltage V0 to an AC voltage to be supplied to a motor, said inverter comprising:

  • a voltage divider connectable to the main battery and having three output terminals including a first terminal, a second terminal and a middle terminal, said voltage divider producing a voltage of V0 /2 across the first terminal and the middle terminal, and a voltage V0 /2 across the second terminal and the middle terminal;

    a first upper arm including a first switching device and a second switching device;

    a first lower arm including a third switching device and a fourth switching device, said first, second, third and fourth switching devices being connected in series, and a connecting point of said second and third switching devices being connected to a U-phase output line;

    a second upper arm including a fifth switching device and a sixth switching device;

    a second lower arm including a seventh switching device and an eighth switching device, said fifth, sixth, seventh and eighth switching device being connected in series, and a connecting point of said sixth and seventh switching devices being connected to a V-phase output line;

    a third upper arm including a ninth switching device and a tenth switching element;

    a third lower arm including a eleventh switching device and a twelfth switching device, said ninth, tenth, eleventh and twelfth switching device being connected in series, and a connecting point of said tenth and eleventh switching devices being connected to a W-phase output line;

    a first diode connected between the middle terminal of said voltage divider and a connecting point of said first and second switching devices;

    a second diode connected between the middle terminal of said voltage divider and a connecting point of said third and fourth switching devices;

    a third diode connected between the middle terminal of said voltage divider and a connecting point of said fifth and sixth switching devices;

    a fourth diode connected between the middle terminal of said voltage divider and a connecting point of said seventh and eighth switching devices;

    a fifth diode connected between the middle terminal of said voltage divider and a connecting point of said ninth and tenth switching devices;

    a sixth diode connected between the middle terminal of said voltage divider and a connecting point of said eleventh and twelfth switching devices;

    detecting means for detecting a voltage across two output lines of said inverter; and

    control means for pulse width modulation control switching of said first to twelfth switching devices for selectively controlling the line-to-line voltages of said inverter for a two-level mode or a three-level mode of operation, said line-to-line voltage being ±

    V0 /2 and 0 in said two-level mode, and being ±

    V0, +V0 /2 and 0 in said three-level mode, said control means being responsive to said detecting means for controlling said inverter to be in the two-level mode of operation when the line-to-line voltage detected by said detecting means is lower than a predetermined reference voltage, and to be in the three-level mode when the line-to-line voltage detected by said detecting means is higher than the predetermined reference voltage.

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