Patent ID: 8410736

Claim:
An electric motor, comprising: three phase windings, and a an inverter controllable device comprising: an inverter including three switch element groups connected in parallel, each switch element group including at least two switch elements connected in parallel, each switch element including an upper bridge-arm switch and a lower bridge-arm switch; a control panel for generating a pulse width modulation (PWM) waveform; and a drive panel for generating a drive voltage according to the PWM waveform to drive the upper bridge-arm switch and the lower bridge-arm switch of each switch element to connect or break separately, and to drive the upper bridge-arm switches in the same switch element group to connect or break synchronously and to drive the lower bridge-arm switches of the same switch element group to connect or break synchronously; wherein each phase winding of the three-phase windings is electrically connected with each junction point between the upper bridge-arm switch and the lower bridge-arm switch in the switch element group; and a d-axis voltage and a q-axis voltage of the motor is adjusted according to the following formula: when V<V N , UdGd=R*IdGd UqGd=R*IqGd; when V≧V N , UdGd=Lq*v*IqGd+R*IdGd UqGd= −( Ld*IdGd +ψ)* v+R*IqGd, where V represents a rotating speed of the electric motor, V N represents a predetermined rotating speed, UdGd represents the d-axis voltage, UqGd represents the q-axis voltage, R represents a resistance of the three-phase windings in the electric motor, IdGd represents a d-axis current, IqGq represents a q-axis current, Ld represents an inductance which a motor stator generates along the d-axis, Lq represents an inductance which the motor stator generates along the q-axis; and ψ represents a permanent magnet flux of the motor rotor.