The air conditioner motor is one of the most important components of the air conditioner. Without the motor, the air conditioner loses its meaning.
Air-conditioning motors mainly include compressors, fan motors (axial fans and cross-flow fans), and swinging air supply blades (stepping motors and synchronous motors). In order to understand the working principle of air-conditioning motors in more detail, we classify and explain them in detail!
01
Principle of compressor motor
1. Single-phase asynchronous motor
Single-phase compressors for air conditioners have two windings, namely the starting winding and the running winding (main winding), and three terminals, which are the common terminal, the starting terminal and the running terminal, which are generally driven by capacitor operation and implement constant speed control.
During the process of starting the motor to the normal operation, the auxiliary winding circuit is always connected with a capacitor in series, so that the electrical appliance has good running performance, high efficiency and power factor, and works reliably.
2. Three-phase asynchronous motor
Its structure is similar to that of a single-phase motor. The difference is that the stator of a three-phase motor is composed of three sets of completely symmetrical windings. These three windings are embedded in the stator core slots and are staggered by 120° electrical angle in spatial distribution.
The three windings can be connected in a Y shape or a △ shape. When three-phase symmetrical currents are passed into the stator windings (that is, the three-phase currents differ by 120° in terms of time and phase), the The air gap between the rotors generates a rotating magnetic field, which causes the rotor to generate electromagnetic torque due to electromagnetic induction.
The three-phase asynchronous motor has a simple structure and excellent performance. The torque, efficiency and power factor are higher than those of the single-phase asynchronous motor. Therefore, air conditioners with higher power, such as cabinet air conditioner compressors, mostly use three-phase asynchronous motors.
3. Frequency conversion motor
As long as the power frequency of the asynchronous motor is changed, different motor speeds can be obtained.
Variable frequency speed regulation can not only achieve smooth speed regulation, but also has a wide speed regulation range, high efficiency, fast response, small starting current, little impact on the power grid, and good comfort performance. It is an energy-saving ideal speed regulation method.
In particular, heat pump air conditioners can control the amount of heat generated by the heat pump through variable frequency speed regulation, which is not limited by the outdoor temperature, thus greatly improving its heating capacity.
The working process of the frequency converter: the frequency converter generally adopts the indirect frequency conversion (AC-DC-AC) method, which is composed of two processes: rectification and inversion.
The power frequency (50Hz) grid current is sent to the rectifier module (such as a diode rectifier bridge) after preprocessing such as power supply filtering, and the rectified DC power is directly input to the inverter module (such as the IPM module using IGBT as the basic component).
The inverter module converts the direct current into alternating current of different frequencies under the action of the driving signal of the CPU chip, and supplies the compressor to work.
Working principle of IPM inverter module: IPM module uses IGBT (Insulated Gate Bipolar Transistor) as a switching element.
The six drive signals sent by the CPU (that is, as the IGBT base signal) respectively control the on-off of the six IGBT switches of the three-phase inverter circuit.
In each cycle, the on-off of each IGBT is controlled in turn according to a certain order every 60°, so as to obtain a three-phase alternating current of a certain frequency at the output end of the inverter circuit.
By controlling the length of the on-off time of the IGBT switch (that is, controlling the pulse width of the positive half cycle and the negative half cycle of each phase), alternating currents of different frequencies can be obtained at the output terminals of the three phases.
02
The principle of fan motor
The motor used for the fan of the air conditioner is generally a single-phase asynchronous motor, which adopts the PSC wiring method.
According to the needs of use, the speed of the fan motor can be adjusted. The speed adjustment methods include: stator winding tapped speed regulation, thyristor speed regulation, etc.
1. Tap type speed regulation
By changing the number of turns of the motor stator winding, the working voltage on the main winding is changed, so as to achieve the purpose of changing the magnetic flux and adjusting the speed. The stator winding of the PSC motor with tap speed regulation is composed of three parts: the main winding, the auxiliary winding and the middle winding (speed regulating winding).
2. SCR speed regulation
Thyristor, also known as thyristor, has two types: one-way thyristor and two-way thyristor. One-way thyristor has characteristics. When the thyristor is subjected to a forward anode voltage, a forward voltage is applied to the gate and there is a certain gate current. , the element is turned on.
When the tube is turned on, the gate will lose its function. When the thyristor is turned on, only when its positive anode voltage decreases to a certain value or the anode voltage becomes negative, the tube is turned off.
Triac characteristics, when the tube is on, when the voltage drops below the minimum voltage to maintain conduction or becomes reversed, the tube is cut off, and can be turned on again until the next trigger signal (pulse signal) arrives.
Solid State Relay: Solid State Relay is abbreviated as SSR, which is a non-contact semiconductor relay using a bidirectional thyristor.
When a trigger signal is applied at the input, the photo-thyristor controls the load on and off.
In the speed regulation of the fan motor of the air conditioner, the high and low levels output by the single-chip microcomputer are used as the trigger signal of the solid state relay, and the zero-crossing point of the power frequency sinusoidal current is detected through the auxiliary circuit, and the timing is controlled by the program, and then the load is turned on at a certain time. the current.
When the power supply current crosses the zero point, the thyristor is automatically turned off, so that the load can obtain the required effective voltage. If this voltage is supplied to the motor, the motor winding voltage can be changed to obtain the corresponding speed.
03
Principles of motors used in other air conditioners
1. Stepper motor
A stepping motor is an executive element that converts electrical pulse signals into linear displacement or angular displacement, that is, when a pulse signal is applied to the motor, the motor moves one step.
The rotor is a cylindrical two-pole permanent magnet rotor made of permanent magnets. The inner circle of the stator and the outer circle of the rotor have a certain eccentricity, so the air gap is uneven, and the air gap is the smallest, that is, the magnetic resistance is the smallest.
A concentrated winding is set in the stator armature, and electric pulse signals are added to both ends of the winding by a special power supply. When the stator winding is not energized, there is a magnetic flux generated by the permanent magnet rotor in the magnetic circuit of the motor.
This flux will tend to the axis of the rotor poles towards the position in the magnetic circuit where the reluctance is minimal.
When the power supply adds a pulse to the motor winding, the polarities of the two magnetic poles of the stator and the two magnetic poles of the rotor repel, and the rotor rotates counterclockwise about 180° in the direction of the arrow n until the stator magnetic pole and the rotor magnetic pole are opposite.
2. Permanent magnet synchronous motor
The micro-motor used in the air-conditioning outlet grill swing blade device is a permanent magnet synchronous claw-pole self-starting synchronous motor.
The driving voltage of the motor is ~220V/50Hz, and its stator consists of a cup-shaped casing, an annular single-phase coil and claw pole pieces; the rotor is a ferrite ring with high coercivity.
The claw poles are evenly distributed along the circumference, and the number of claw pole pairs (magnetic pole pairs) is determined by the required synchronous speed. The swing motor has many claw pole pairs, low speed, large torque, small output power, simple structure and no fixed steering.
The master switch is usually installed on the control panel of the air conditioner. It is the power switch to connect the compressor, fan and other executive equipment, and also the selector switch to switch the running state of the air conditioner.
