The voltage is also called the potential difference, which is the difference between the two potentials from the high potential to the low potential. Usually called voltage.
Expressed by the letter U, the unit is volts, denoted by the letter V.
Where: 1V=1000mV=1000,000μV 1mV=1000μV
The voltage is also divided into AC and DC, which are represented by ACV and DC V respectively.
DC voltage should be noted when measuring, there are +, - points.
2. Resistance:
The resistance encountered by the current flowing in the object is called resistance, expressed in R. The unit: ohm is represented by the letter Ω.
Among them, 1MΩ=1000KΩ=1000,000Ω
1KΩ=1000Ω
There are many types of resistors, such as carbon resistors, carbon film resistors, and wirewound resistors. Formally there are fixed resistors, variable resistors and potentiometers.
Temperature coefficient of resistance: When the current flows through the resistor, the temperature rises, and the resistance value changes. The ratio of the resistance value to the original resistance is called the temperature coefficient of the resistor. For the resistance of metal materials, the resistance increases with the increase of temperature, which is a positive temperature coefficient; for stone grinding and carbon, the resistance decreases with the increase of temperature, which is a negative temperature coefficient. The smaller the temperature coefficient, the more stable the resistance.
The temperature sensor of an air conditioner is also a kind of resistor, called a thermistor, whose resistance decreases as the temperature increases.
The rated power is divided into 1/8, 1/4, 1/2, 1, 2, 3, 5, 10, 20W and other specifications.
When measuring the resistance with a pointer multimeter, be careful to select the appropriate gear position, and the shift must be zero.
3. Capacitor:
The combination of two conductors separated by an insulator is called a capacitor. Expressed by the letter C, the unit is Farah, denoted by F.
Among them, 1F=1000000μF=106μF=1012μF
The main indicators are capacitance and withstand voltage, such as 2.5μF/450V.
There are mica capacitors, ceramic capacitors, electrolytic capacitors and paper capacitors.
Generally, ceramic capacitors are used in high-frequency circuits, and the starting capacitors of motors are mainly electrolytic capacitors.
When measuring the capacitance, put the multimeter pen probe directly on the two terminals of the capacitor, and the digital meter can directly read the capacity of the capacitor. When measuring with the pointer meter, use the multimeter's resistance file and set the resistance file to the maximum range. If the pointer deflection angle is large, then gradually return to the initial position (∞ position), indicating that the capacitor is good. If the position is not returned, the resistance of the meter head is the leakage resistance. Generally, the leakage resistance of the capacitor is very large, usually tens to hundreds of megaohms. Measure the large capacitance of 0.01μ or more, and use the multimeter RX10K file. As long as the head pointer swings little or does not jump, it can be judged that the capacitor has been opened.
The capacitance of the capacitor is different, and the angle at which the pointer is deflected is also different.
4. Transformer:
The transformer consists of a coil and a core that are used to change the voltage. The transformer is mainly used in the air conditioning control circuit, and the function is to reduce the voltage of the AC power supply to a certain value and then send it to the rectifier circuit.
Working principle: The current passing through the primary coil will induce a corresponding potential on the secondary coil. The level of the induced potential is related to the number of turns of the primary and secondary coils. If the number of turns of the secondary coil of the transformer (number of turns) Less than the primary, it is a step-down transformer, and vice versa.
The formula is:
Primary voltage (U1) / secondary voltage (U2) = primary turns / secondary turns
The transformer can only change the voltage and cannot increase the power.
The transformer generally has a thermal fuse inserted in the primary coil. When the transformer coil temperature is too high, it can be protected by a fuse. However, after the fuse is blown, it cannot be recovered, and the replacement of the fuse is lack of operability. Therefore, the method of replacing the transformer is generally used, which causes great waste.
At present, the company's research institute is conducting experimental work on recoverable temperature protection devices and is ready to use them on some products.
5. Inductance:
The inductance is a physical quantity that measures the size of the self-inductive flux of the coil. It is represented by the letter L, and the unit is Henry, which is represented by the letter H.
Among them, 1H=103mH=106μH
The inductance is divided into mutual inductance and self-inductance.
(1) Mutual inductance: The electromagnetic induction between two coils is called mutual inductance. Such as current transformers.
(2) Self-inductance: The electromagnetic induction caused by the current change through the coil itself is called self-inductance.
6. AC contactor:
An AC contactor is an automatic controller that uses electromagnetic force to turn the circuit on and off.
The structure of the AC contactor is mainly composed of an electromagnetic system (iron core, coil) and contacts. The coil has a core fixed, and when the switch coil is energized, the core coil generates electromagnetic attraction, so that the moving iron core is sucked. At the same time, the moving iron core drives the three moving contacts to move downwards to contact the three static contacts, so that the power source can be sent from the input end of the contactor to the output end of the contactor.
The circuit of the AC contactor is divided into two parts: the main circuit and the control circuit. Usually, the load power supply circuit is called the main circuit, and the coil on/off control circuit is called the control circuit. The main circuit includes power supply circuits such as motors and electric heaters, and the control circuit has circuits such as overvoltage, overcurrent, undervoltage, overtemperature protection, and pressure protection.
When using an AC contactor, the current level should be selected according to the principle that its current is not less than the load rating. For example, the rated current of the motor is 8.6A, and a 10A AC contactor should be used.
7. Thermal relay: (TH type overcurrent relay)
A thermal relay is a protective relay that operates with a current effect and is mainly used for overload protection of a motor.
The thermal relay consists of a bimetal, a heating element, an action mechanism, and a contact system. The bimetal is made of two pieces of metal with a large difference in expansion coefficient. In use, the heating element is connected in series with the motor power supply and the contacts are connected in series in the contactor coil control circuit. When the motor is overloaded, the current is large, so that the bimetal is bent by heat. Through the action mechanism, the movable contact and the static contact are disconnected, the contactor coil is de-energized, and the motor is disconnected from the power source, thereby protecting.
This relay consists of a manual adjustment knob that allows you to select the desired current value. Fast break contact points are automatically reset and manually reset.
When selecting, according to the rated current of the motor, select the rated current of the thermal relay. If the rated current of KFR-72LW/D is 7.2A, select 10A thermal relay and adjust the current value to 7.2A.
8. Motor:
Fans for air conditioners include centrifugal fans, axial fans, and cross-flow fans. The speed of the motor generally has three levels: high, medium and low. The air supply has strong, medium and weak points.
Fan motors typically use a single capacitive sensing type.
Capacitive induction motors have two windings, the start winding and the running winding. The two windings are spatially different by 90 degrees. A large-capacity capacitor is connected in series on the starting winding. When the running winding and the starting winding pass through a single alternating current, the current in the starting winding is advanced by 90 degrees from the current of the running winding due to the action of the capacitor, reaching the maximum first. value. Two identical pulsed magnetic fields are formed in time and space, so that a rotating magnetic field is generated in the air gap between the stator and the rotor. Under the action of the rotating magnetic field, an induced current is generated in the rotor of the motor, and the current interacts with the rotating magnetic field. The electromagnetic field torque causes the motor to rotate.
The fan motor used in the Xinfei air conditioner is a single-phase AC asynchronous motor. However, according to the actual use requirements, the speed is adjustable and the speed is not adjustable. The outdoor fan motor of the air conditioner is a single-speed motor, and its rotation speed is not adjustable. While the indoor motor is in use, because the user has different speed requirements, and also needs to meet other functions of the air conditioner, the indoor fan motor can be adjusted in speed.
The indoor motor is divided into a tap motor and a PG motor according to the way of its speed regulation.
The tapping motor generally has three taps, which can form three speeds. These motors are used in our company's cabinet products.
A PG motor is a motor with a Hall element. The Hall element is mounted inside the motor. Normally, the Hall element outputs one or several pulse signals every revolution. When the fan motor speed is high, the output pulse signal frequency is high; when the fan motor speed is low, the output pulse signal frequency is low. The output pulse signal is collected by the single-chip microcomputer, and then the operating voltage of the PG motor is adjusted by adjusting the conduction angle of the thyristor, and the wind speed is automatically controlled.
Both the tap motor and the PG motor have advantages and disadvantages: the tap motor control method is simple, but the motor needs to increase the winding tap, the process is complicated, and the control part needs three relays to control three speeds, using many parts and high cost; and the PG motor The control speed is accurate, but the motor needs to increase the Hall element, and the control part also needs to increase the pulse detection circuit and the zero-crossing detection circuit, and the control is complicated.
In view of the advantages and disadvantages of the tapping motor and the PG motor, some manufacturers currently adopt an open-loop control scheme that controls the motor speed through the thyristor voltage regulation: that is, according to the experimental results of the whole machine, it is determined that the air conditioner has high, medium and low winds. Control the conduction angle of silicon, write to the microcontroller to directly adjust the control voltage of the fan motor, so as to achieve the purpose of speed regulation. Since this method reduces the number of circuits of the Hall element and the control system, this method can reduce the cost, but the accuracy of the speed control is not high.
Most of our company's on-board air conditioners use PG motors.
9. Three-phase motor:
Cabinet air conditioners with large cooling capacity often use three-phase motors, mainly compressors, which are generally more than three air conditioners. The advantage of using three-phase power is high efficiency, large starting torque, and can be started directly. If single-phase 220V power supply is used, the air conditioner will start to be difficult to operate when the voltage is low, and it will not work properly.
The three-phase motor only draws three power lines to the outside, and the power supply voltage between the phases is 380V. The windings of the three-phase motor are connected by a triangle and a star. In the above figure, (a) is a star connection and (b) is a delta connection.
Three-phase motors have high starting torque, high efficiency and power factor, so there is no need to use capacitors and start relays, but because the power is generally large, they are usually powered by AC contactors.
When the air conditioner reports a phase failure, it is generally a phase loss or phase inversion of the three-phase power. First check whether the three-phase power has electricity. If the phase is missing, there is a phase failure or the internal line of the power line is broken. Electric, just change any two connected wires.
If the KFR-120LW/D06 air conditioner appears "E7", the occurrence of "E0" in the KFR-72LW/D is a phase problem.
electric
Electrical main circuit diagram
10. Stepper motor:
The stepping motor is a control system execution component with high running precision and good control characteristics. It works in a pulsed manner, and each time one or several pulses are received, the rotor of the motor moves one position and the distance traveled can be small.
The difference between a stepper motor and a normal motor is that the stepper motor receives the control of the pulse signal. Stepper motor* An electronic switching device called a ring distributor that turns the field windings into DC power in sequence through a power amplifier. Since the field windings are arranged in a certain regularity in space, a rotating magnetic field with a step change is formed in the space after the turn-on and the DC power source are turned on, so that the rotor rotates stepwise, and as the pulse frequency increases, the rotation speed It will increase.
The more commonly used stepping motors include reactive stepping motors, permanent magnet stepping motors, hybrid stepping motors, and single-phase stepping motors. The rotor of the reactive stepping motor is made of soft magnetic material, and the multi-phase excitation winding is arranged on the stator, and the torque is generated by the change of the magnetic permeability. At this stage, reactive stepper motors get the most applications.
Stepper motor features:
(1) The system control inertia is good and the speed is fast;
(2) The output pulse is accurate;
(3) Strong real-time performance;
(4) Good anti-electromagnetic characteristics and strong anti-interference ability.
The fan drive motor on the air-conditioner hangs and the closed wind guide drive motor on the cabinet are all stepper motors.
11. Relay:
A relay is an actuator of the control circuit and consists of a coil, a set or sets of reeds with contacts. According to the use, it can be divided into AC relay and DC relay.
The relay is indicated by the letter K. The contacts of the relay are divided by moving and stationary contacts. The figure below shows the relay in the circuit type, where (B) consists of two pairs of moving and stationary contacts.
The working principle of the relay is: when the relay is energized, the iron core is magnetized to generate a sufficient electromagnetic force, the armature is sucked and the reed is driven to close the movable contact and the static contact; when the coil is de-energized, the electromagnetic attraction disappears. Reeds bring the armature back
The original position separates the moving contact from the stationary contact. As long as the circuit to be controlled is connected to the contact, it can be controlled by the relay.
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