Permanent Magnet Synchronous Motor Solution for High-speed Mixer

1. Market basics

With the improvement of living standards, people's awareness of health preservation has become stronger and stronger. The blender with rich recipes and health functions, as a kitchen appliance that replaces the blender, has become a star product on the market in the last year.

2. Market demand or improvement point

The current mixer motors on the market generally use AC series motors. The AC series motors are composed of rotor iron core, stator excitation winding, rotor working winding, commutator and carbon brush. The rotor winding is wound around the rotor iron Above the core, the stator winding is wound on the stator iron core, and the rotation of the motor is realized by the contact between the carbon brush and the commutator to change the energization sequence of the winding to realize the rotation of the motor. In this way, the motor is subject to the working principle, the motor efficiency is low, the load speed is seriously decelerated compared to the no-load speed, and constant speed and constant torque control cannot be performed. When encountering fluctuating loads, the speed and output torque fluctuate. , and the output torque is low at low speed. In addition, when such motors rotate, there is mechanical friction between the carbon brushes and the commutator, resulting in very loud noise and a large amount of dust generated by the friction of the carbon brushes, which may contaminate food.

3. Our high-speed mixer motor solution

The structure of the motor is composed of stator iron core, rotor iron core, winding, insulating frame, permanent magnet, front/rear end cover, balance block, fan blade, terminal board, bearing, motor lead wire, etc. The stator and rotor cores are made of laminated silicon steel sheets, and the permanent magnets are made of rare earth permanent magnets. The winding is wound on the stator core, and the number of stator winding elements is a multiple of 3. The permanent magnets are embedded in the rotor core, with an even number of pairs of poles, and the magnetic poles facing the rotor surface are arranged in sequence N and S. The rotor iron core is provided with an inner groove for placing the permanent magnets, and the surface of the rotor iron core is designed as a bread-shaped protrusion to reduce the cogging torque. Balance blocks are respectively set on both ends of the rotor core for dynamic balancing by de-weighting method. The front and rear covers are connected by screws, and the stator core is fixed. The front cover is attached to the customer's mixer. A plastic insulating skeleton is arranged between the stator iron core and the windings, and the two skeletons are inserted into each other to completely wrap the stator iron core to prevent poor insulation. A wiring PCB board is arranged on the end face of the motor winding, so as to connect the motor lead wire and the winding phase wire. A centrifugal fan blade for heat dissipation is arranged at the tail of the motor rotor.

The driver part is composed of high-voltage AC-DC conversion circuit, EMC circuit, low-voltage sampling and control circuit, power circuit and so on. Among them, low-voltage sampling and signal feedback all adopt signal isolation, and the main control chip in the control circuit adopts high-performance DSP chip, which has the advantages of floating-point operation and fast operation, and has considerable advantages in high-end motor control. The power device adopts 600V 30A integrated IGBT module, which is small in size and large in power.

In order to realize constant speed, constant torque control, low speed and high torque and no Hall control, the software algorithm plans to combine the magnetic field vector control technology and the latest international high frequency injection method control technology to accurately provide the DQ axis inductance of the motor. , phase resistance, back EMF constant and other parameters to achieve accurate Hall-free control of the motor.

The rotation of the motor is realized by the driver to control the energization sequence of the windings. There is no mechanical friction. The sensorless FOC control is performed by the high-performance driver, and the rare earth permanent magnet is used to solve the high noise of the AC series motor. A series of shortcomings such as speed drop, torque fluctuation, low speed powerlessness, toner pollution, low efficiency, large volume, and low power density can greatly improve the customer experience of the mixer and allow customers to expand more menu functions.

4. The future optimization direction and achievable goals of specific application solutions

4.1 key technology

Through advanced algorithms such as field-oriented control, direct torque control and high-frequency injection method, constant speed, constant power, low speed and high torque, low noise, high efficiency, green environmental protection, and long service life are realized.

4.2 Innovation

• The torque is constant, the speed is constant and multi-speed adjustable, and the speed of the stirring motor is not as serious as that of the series motor, and the stirring effect is very good.

• The motor has a large torque at low speed and can easily break hard substances.

• Low noise, there is no mechanical friction between the mechanical carbon brush and the commutator, so the noise is greatly reduced

• High efficiency, the motor efficiency of the brushless motor can reach 85%, and there is a relatively wide efficiency range. The AC series motor is only 30%~60%

• Green and environmental protection, the series motor produces dust pollution due to carbon brush wear, which is not environmentally friendly, while the permanent magnet synchronous motor does not have carbon brushes and there is no dust pollution

• Long life, the life of the series motor is only a few hundred to one thousand hours due to the easy wear and tear of the carbon brush, while the life of the permanent magnet synchronous motor is at least 5000 hours.