Harmonic motor, German Harmonic model, Harmonic price

Harmonic motor refers to a low-power single-phase asynchronous motor powered by a single-phase AC supply (AC220V). This type of motor typically has two-phase windings on the stator, and the rotor is of the standard squirrel-cage type. Different distributions of the two-phase windings on the stator and different power supply conditions can produce different starting and operating characteristics.

Harmonic motor working principle

Motor direct torque control method. This method analyzes the mathematical model of the AC motor in the stator coordinate system, emphasizing direct control of the motor torque under the condition of an approximately circular rotating magnetic field, eliminating complex calculations such as vector coordinate transformation. Its field orientation uses stator flux linkage, which can be observed by knowing only the stator resistance, making it less susceptible to changes in motor parameters compared to vector control. In recent years, direct torque control has been applied to the control of permanent magnet synchronous motors, and its control laws and key technologies are gradually being understood and mastered. Direct torque control has broad application prospects in fully digital, high-torque, fast-response AC servo systems. Nonlinear control: AC motors are strongly coupled, nonlinear, multivariable systems. Nonlinear control achieves dynamic decoupling and global linearization of the system through nonlinear state feedback and nonlinear transformation, decomposing the nonlinear, multivariable, strongly coupled AC motor system into two independent linear single-variable systems. The rotor flux linkage subsystem consists of two inertial links. The regulators for the two subsystems are designed separately according to linear control theory to achieve the expected performance indicators. However, the basis for feedback linearization of nonlinear systems is a motor model with known parameters and precise measurement or observation of the system. During operation, motor parameters change due to various factors, and the accuracy of flux linkage observation is difficult to verify, all of which affect the robustness of the system and may even cause performance degradation. However, this control method still needs further improvement. Adaptive control can continuously extract information about the model during system operation, gradually improving the model, and is a powerful means to overcome the influence of parameter changes. Adaptive methods applied to permanent magnet AC motor control include model reference adaptive control, parameter identification self-tuning control, and various newly developed nonlinear adaptive controls. However, all these methods have problems: (1) complex mathematical models and calculations complicate the control system; (2) identification and correction require a process, so for systems with rapid parameter changes, it is difficult to achieve good results because correction cannot keep up. Sliding mode variable structure control is a control strategy of variable structure control. Its fundamental difference from conventional control lies in the discontinuity of control, i.e., a switching characteristic that causes the system "structure" to change at any time. Its main feature is to purposefully make the system move along a designed "sliding mode" trajectory based on the deviation of the controlled variable and its derivative. This sliding mode can be designed and is independent of system parameters and disturbances, thus giving the system strong robustness. In addition, sliding mode variable structure control does not require any online identification, so it is easy to implement. Over the past 10 years, applying sliding mode variable structure control to AC drives has been a research hotspot for scholars domestically and internationally, and some effective results have been achieved. However, the inherent discontinuous switching characteristic of sliding mode variable structure control causes a "chattering" problem in the system. The main reasons are: (1) for actual sliding mode variable structure systems, the control force is always limited, resulting in limited system acceleration; (2) system inertia, time-space lag of switching switches, and errors in state detection, especially for computer sampling systems, form "quasi-sliding modes" when the sampling time is long. Therefore, "chattering" inevitably exists in actual systems and cannot be eliminated, which limits its application.

Harmonic motor structure

The motor consists of stator poles, rotor, brushes, housing, etc. Stator poles use permanent magnets (permanent steel), including materials such as ferrite, AlNiCo, and NdFeB. According to their structural form, they can be divided into cylindrical and tile types, among others. The rotor is generally made of laminated silicon steel sheets, with enameled wire wound between two slots of the rotor core (three slots mean three windings), and each joint is soldered to the metal segments of the commutator. Brushes are conductive components connecting the power supply to the rotor windings, possessing both conductivity and wear resistance. Permanent magnet motor brushes use single-metal strips, metal graphite brushes, or electrographite brushes. 2. Brushless DC motor: consists of a permanent magnet rotor, multi-pole winding stator, position sensors, etc. The characteristic of brushless DC motors is the absence of brushes; they use semiconductor switching devices (such as Hall elements) to achieve electronic commutation, replacing traditional contact commutators and brushes. It has advantages such as high reliability, no commutation sparks, and low mechanical noise. Position sensors commutate the current in the stator windings in a certain order according to changes in rotor position (i.e., detecting the position of rotor poles relative to stator windings, generating position sensor signals at determined positions, processing them through signal conversion circuits to control power switch circuits, and switching winding currents according to a certain logical relationship). There are three types of position sensors: magnetic, photoelectric, and electromagnetic. For brushless DC motors using magnetic position sensors, magnetic sensing devices (such as Hall elements, magnetic diodes, magnetic transistors, magnetic resistors, or dedicated integrated circuits) are installed on the stator assembly to detect changes in the magnetic field generated by the rotation of the permanent magnet rotor. Hall elements are commonly used in electric vehicles. For brushless DC motors using photoelectric position sensors, photoelectric sensing devices are configured at specific positions on the stator assembly, and a light-blocking plate is installed on the rotor, with the light source being an LED or a small bulb. When the rotor rotates, due to the action of the light-blocking plate, the photosensitive components on the stator will intermittently generate pulse signals at a certain frequency. For brushless DC motors using electromagnetic position sensors, electromagnetic sensor components (such as coupling transformers, proximity switches, LC resonant circuits, etc.) are installed on the stator assembly. When the position of the permanent magnet rotor changes, the electromagnetic effect causes the electromagnetic sensor to generate a high-frequency modulated signal (whose amplitude varies with rotor position). The operating voltage of the stator windings is provided by an electronic switch circuit controlled by the output of the position sensor.

Harmonic motor maintenance methods

When the no-load current of the motor exceeds the limit data, it indicates that the motor has failed. Reasons for high no-load current include large internal mechanical friction, partial short circuits in coils, and demagnetization of magnetic steel. We continue with relevant tests and inspection items to further determine the cause or location of the fault. When the no-load/load speed ratio of the motor is greater than 1.5, turn on the power, rotate the throttle, and let the motor run at high speed no-load for more than 10s. After the motor speed stabilizes, measure the maximum no-load speed N1 of the motor at this time. Under standard test conditions, after traveling a distance of more than 200m, start measuring the maximum load speed N2 of the motor. No-load/load speed ratio = N2 ÷ N1. When the no-load/load speed ratio of the motor is greater than 1.5, it indicates that the demagnetization of the motor's magnetic steel is quite severe, and the entire set of magnetic steel inside the motor should be replaced. In actual electric vehicle maintenance, the entire motor is generally replaced. The direct cause of motor heating is high current. The relationship between motor current I, motor input electromotive force E1, motor rotational induced electromotive force (also called back EMF) E2, and motor coil resistance R is: I = (E1-E2) ÷ R. An increase in I indicates that R has decreased or E2 has reduced. A decrease in R is generally caused by coil short circuits or open circuits, while a reduction in E2 is generally caused by magnetic steel demagnetization or coil short circuits/open circuits. In the practice of whole-vehicle electric vehicle maintenance, the method for handling motor heating faults is generally to replace the motor. Whether high-speed or low-speed, motors should not exhibit mechanical collisions or discontinuous, irregular mechanical noise during loaded operation. Different types of motors can be repaired using different methods. The reasons for short driving range and weak motor power (commonly known as lack of power) are relatively complex. However, after excluding the above 4 types of motor faults, generally speaking, the fault of short whole-vehicle driving range is not caused by the motor, but is related to battery capacity attenuation, charger inability to fully charge, controller parameter drift (PWM signal not reaching 100%), etc. Phase loss in brushless motors is generally caused by damage to the Hall elements of the brushless motor. We can determine which Hall element has failed by measuring the resistance of the Hall element output leads relative to the Hall ground and Hall power leads using the comparison method. To ensure the precision of motor commutation position, it is generally recommended to replace all three Hall elements simultaneously. Before replacing Hall elements, it is necessary to clarify whether the motor's phase electrical angle is 120° or 60°. Generally, for 60° phase angle motors, the three Hall elements are placed in parallel. For 120° phase angle motors, the middle Hall element of the three is placed in a flipped 180° position.

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