Method for controlling start-up phase of permanent magnet synchronous motor

#Pursuant to 35 U.S.C. § 119 and the Paris Convention Treaty, this application claims foreign priority to Chinese Patent Application No. 201910389348.7 filed May 10, 2019, the contents of which, including any intervening amendments thereto, are incorporated herein by reference. Inquiries from the public to applicants or assignees concerning this document or the related applications should be directed to: Matthias Scholl P. C., Attn.: Dr. Matthias Scholl Esq., 245 First Street, 18th Floor, Cambridge, Mass. 02142.

#The disclosure relates to a method for controlling the start-up phase of a permanent magnet synchronous motor.

#Conventionally, the control method of a sensorless permanent magnet synchronous motor includes a constant torque control mode, a constant speed control mode and a constant air volume control mode.

#FIG. 1 is a block diagram of a constant torque control of a sensorless permanent magnet synchronous motor in the prior art.

#FIG. 2 is a principle diagram of the vector control of a sensorless permanent magnet synchronous motor.

#FIG. 3 is a perspective view of a permanent magnet synchronous motor according to one embodiment of the disclosure.

#As shown in FIG. 3, FIG. 4 and FIG. 5, there provided is a three-phase permanent magnet synchronous motor comprising a motor unit 1 and a motor controller 2. The motor unit 1 comprises a stator assembly 12, a rotor assembly 13 and a housing assembly 11; the stator assembly 12 is mounted on the housing assembly 11; the rotor assembly 13 is nested in or outside the stator assembly 12; the motor controller 2 comprises a control box 22 and a control circuit board 21 mounted therein; the control circuit board 21 comprises a power circuit, a microprocessor, a bus voltage sensing circuit, and an inverter; the power supply circuit supplied power to each part of the circuit. The DC bus voltage Uabc is input to the microprocessor by the bus voltage detection circuit; the microprocessor controlled the inverter which controls the on and off of the coil windings in each phase of the stator assembly 12.

#As shown in FIG. 6 and FIG. 7, suppose that the line current sensing circuit of the three-phase permanent magnet brushless DC motor input the phase currents ia, ib, and ic to the microprocessor. Then the DC bus voltage Vbus is output from one end of the capacitor C1 after the AC INPUT passed through the full-wave rectification circuit consisting of diodes D7, D8, D9, and D10, wherein the DC bus voltage Vbus is related to the input AC voltage. Six PWM signals (P1, P2, P3, P4, P5, P6) are calculated by a microprocessor and then input into an inverter through six electronic switch tubes (Q1, Q2, Q3, Q4, Q5, Q6) on the inverter, respectively.

#As shown in FIG. 2, the basic working principle of a permanent magnet synchronous motor based on sensorless vector control is briefly described as follows: the permanent magnet synchronous motor is regarded as the interaction effects of rotating magnetic field between a stator and a rotor. There are two coordinate systems in the figure, one is a rotating coordinate system—DQ coordinate system, the other is a stationary coordinate system—ABC coordinate system (which can be converted into a coordinate system where α and β are perpendicular to each other). The rotor rotated at a rotational speed wr under the action of the excitation current if, and the stator rotated at a rotational speed ws under the action of the excitation current is, the resultant vector of the stator in the figure is S; according to the formula of electromagnetic torque: Te=P0·φf×iq  (1) where P0 is a pole pair (constant) of the motor, ψf is a flux linkage generated under the action of the field current if. Based on the rotor is a permanent magnet rotor, when if=0 and ψf is a constant, the formula of electromagnetic torque became: Te=K×iq  (2) where K is a constant, and the electromagnetic torque Te of the permanent magnet synchronous motor is only determined by the q-axis current.