【 Weak current College 】 AC frequency more online and DC inverter multi online works

1 the ability to adapt to the load cannot automatically adapt to load changes automatically adapt to changes in load
2 temperature control precision on/off control, temperature fluctuation range up to 2 ° c, low temperature fluctuation, high-frequency control range 1 ° c
3 start the performance start current is greater than the rated current of soft start, a small start-up current
4 energy saving on/off control, does not automatically to save power, save energy, low-maintenance of 30%
5 low voltage operation performance 180V following difficult to operate low-150V or normal operation
6 refrigeration, heating slow fast
7 hot cold ratio is less than 120% more than 140%
8 low-temperature heating effect 0 ° C to the following effect on poor-10 ° C when is still good
9 defrosting performance accurately and quickly, just half the time of conventional air conditioning
10 dehumidifying performance timing on/off control, dehumidification, apathetic low-frequency operation, not only in dehumidify, health desiccant cooling
11 full-load operation without this feature automatically to run high-frequency strong
12 protection features simple comprehensive
13 simple automatic control performance really obscure, neural network

Inverter air conditioner control features

1. the ability to adapt to the load

Conventional air conditioning refrigeration capacity with the outdoor temperature rise and fall, but the room heat load with the outdoor temperature rise and rise, so that, in the outdoor temperature is higher, the need for air conditioning to the bedroom output more cooling capacity, conventional air-conditioning are often insufficient cooling capacity, comfort, while in the outdoor temperature is low, the need for air conditioning to the bedroom output smaller conventional air-conditioning cooling capacity, often refrigeration capacity of sebum, wasted power. While the inverter air conditioner by compressor speed changes, you can achieve the cooling capacity with the outdoor temperature rise and rise, decline and fall, which implements the refrigerating capacity and room automatic matching of the heat load, improved comfort, saving electricity.

Inverter air conditioner conditioning refrigeration capacity of principle:

Certain conditions, cooling capacity and proportional to the refrigerant mass flow
That is, Q = q.m
Type, Q-cooling capacity
Q — the amount of refrigerant unit quality refrigeration
M-refrigerant mass flow
Certain conditions, the refrigerant mass flow and compressor speed as a function, in direct proportion to the
That is, m = f (N)
-F-refrigerant mass flow and compressor speed as a function of the different structure of this relation different compressor
N — compressor speed
Integrated two-type, you can adjust the compressor speed for air conditioning refrigeration capacity adjustment, this is the DC or AC inverter air conditioner frequency principle of energy regulation.

2. temperature adjustment method

To refrigeration State, for example, to set the temperature press stop, the indoor temperature is higher than the set temperature 1 degree, compressor reopen. Inverter air conditioner temperature adjustment method, the room temperature decrease 0.5 degrees, operation frequency is reduced to a file, on the contrary, the room temperature rise 0.5 degrees, each running a frequency increase, that is, the higher the temperature, the operating frequency increases, so that rapid cooling, air conditioning in room temperature is to set the temperature, the operating frequency, the cooling capacity is also provided, to maintain the set temperature at room temperature, low temperature fluctuation, small nearby.

3. start, running performance

Conventional air conditioning to fixed-frequency starting, constant speed operation. Inverter air conditioner running low frequency start and frequency.

4. energyefficiency

Conventional air conditioning on/off control, compressor switch frequently, less power consumption. -Frequency inverter air conditioning automatically to maintain constant temperature, avoiding compressor basic frequently opened than conventional air conditioning power saving 30%.

5. low voltage operation performance

Conventional air conditioning in voltage lower than 180V or so, the compressor will not boot, and inverter air conditioner in the voltage is low, the reduced frequency start and reduce the load on startup, the minimum starting voltage can be up to 150V.

6. hot-cold than

Conventional air-conditioning refrigeration, heating compressor speed, only through the system matching to improve thermal cooling limitations than that. Inverter air conditioner compressor speed ratio when heat and refrigeration, so when a high number of hot and cold ratio of up to 140%. (Heating Max operating frequency is often higher than the maximum operating frequency of refrigeration high 20Hz left-right)

7. low-temperature heating effect

Conventional air conditioning compressor speed constant, 0 ° C following compressor power is very low, in fact no heating effects; inverter air conditioner to high-frequency operation at low temperature, heating is conventional air-conditioning of 3, 4 times.

8. full-load operation

Conventional air conditioning compressor only one speed, it is not possible to achieve strong at full load; inverter air conditioner in person for a long time, just on time or indoor and outdoor temperature difference is large, you can achieve high strength.

9. the protection function

Conventional air conditioning each current protection are required to stop the compressor; inverter air conditioner whenever an protection are running at the right frequency to be buffered, non-stop protection can be achieved without affecting the user's use.

2. the frequency of the basic principles of air conditioning circuit

Inverter air conditioners based compressor is using AC or DC motor can be divided into AC variable frequency and DC inverter.

1. AC inverter air conditioner

(1) basic principle

Asynchronous motor torque is a stator flux and rotor current interaction. Stator winding through the current rotating magnetic field, while the rotor windings inside the electromotive force, induction, which produced the induced current, the current and the interaction of the stator rotating magnetic field, it produces a magnetic field force. But in fact, for asynchronous motor, rotating magneticField of speed (usually referred to as synchronous speed) n0 and n1 is the rotor speed difference, the difference between the ratio of the synchronous speed, we call it the slip, s, i.e.

Type, f-current frequency
P-motor pole
So the rotor speeds available under-representation n1
Top-style, as long as the change in the power supply frequency induction motor, motor speed will be changed, the AC frequency conversion air conditioning is based on this basic principle to run.
Asynchronous Motors at run time, the EMF E1:
Type, k-motor winding coefficient;
N1 – each phase stator winding turns
Φ — each polar vortex

Because of the pressure drop on the stator resistance is very small and can be ignored, so that we can get by on-the-flux Φ and proportional to the U1/f. For flux Φ, we usually want to stay close to saturation values, if the further increasing the flux Φ, will make the motor core saturation, causing the motor through a lot of exciting current to increase motor copper loss and severe iron loss, due to the winding when overheating damage to the motor. The decrease in flux Φ, core has not been fully utilized, allowing the output torque. In this way, by unknown, at-must remain constant, that is, Φ to maintain U1/f constant, change the frequency f of the motor voltage U1 must at the same time changes, i.e. frequency at the same time also to PSA. This method of regulating speed we call VVVF (VairbleVoltageVaribeFrequency) and known as V/F Inverter control. Now inverter air conditioner control methods are basically use this method to implement frequency.

(3) implementation of V/F frequency controlled method

Pulse width modulation (PWM): output voltage within each half cycle, the output voltage waveform into several pulse wave, due to the average value of output voltage and pulse duty cycle (pulse width divided by pulse cycle known as duty) is proportional, adjust the frequency, not to change the size of the pulse voltage amplitude, but changing the pulse duty cycle, you can achieve the effect of frequency variable also. This method is called PWM (PuleWidthModulation) modulation, PWM modulation can directly in inverter complete voltage and frequency of changes at the same time, the control circuit is relatively simple.

Because of the PWM output voltage waveform and current waveforms are non-sinusoidal wave, has many higher harmonic components, which allows input to motor energy cannot be fully chosen, increased wear and tear. In order to make the output waveform is close to the sine wave, proposed a sine-wave PWM (SPWM).

The so-called SPWM modulation, simply, is a pulse-width modulation, pulse sequence when the duty, in accordance with the rules of a sine wave, i.e., when the change of sine amplitude value is the maximum width of the pulse is also the most, when sine amplitude value is the minimum value, the pulse width is the minimum (as shown in the figure below). Thus, output to the motor pulse sequence can make load current higher harmonic components greatly reduced, thereby improving the efficiency of the motor. SPWM waveform characteristics can be summed up as "constant-amplitude not fixed-width, two narrow Middle width".

(4) specific circuit
For inverter air conditioner of circuits, its interior machine parts and similar to conventional air conditioning, one more than conventional air conditioning distribution circuit. Its main part is concentrated in the outdoor portion of outdoor electronic control with the main control board, power supply circuit, variable frequency drive module. While the core of outdoor frequency variable circuit £ concentrated mainly in the following two aspects:

1) variable frequency drive module

This section refers to the complete DC to AC inverter procedure used to drive inverter compressor operation of the inverter and around the circuit. Inverter air conditioner on the usual six IGBT driver circuit consisting of upper and lower overhead. In practice, the use of IPM (IntelligentPowerModule) module plus the surrounding circuit (such as switching power supply circuit). IPM is an intelligent power module, it will IGBT, together with its driver circuits and multiple protection circuit is packaged in the same module, thus simplifying the design, improving the overall system reliability. Now inverter air conditioner frequently used IPM has Japan's Mitsubishi's PM series and new electric element of Japan TM series (built-in switching power supply circuit).

2) outdoor control chip

As technology advances, the inverter air conditioner control will provide intelligent, integrated, reliable technology direction, and control of core--chips also will become more and more advanced. The main outdoor chip is the complete range of operations, generate SPWM waveform, realization of compressor V/F curve control and provides a variety of protection, etc. Inverter air conditioner use outdoor control chips there are many, such as NEC, Motorola, Mitsubishi, etc. Because the air conditioning technology, fuzzy control technology continues to improve, and that there is a performance better, more powerful control chip — DSP. DSP is DigitalSignalProcessor is short for digital signal processors, compared with General MCU, DSP in computing speed, signal processing, motor control, greater advantages, is the future direction of development.

2. DC inverter air conditioner basic principle and structure

DC inverter air conditioner which is the key to using the BLDC motor as compressors, its control circuit and AC frequency conversion controller, Basic.

(1) DC inverter air conditioner's basic principles

DC inverter concepts

We are using the BLDC motor as the air conditioner compressor is called the "DC inverter air conditioner" conceptually is not exact, because we all know that DC is no frequency, there is no changeFrequency, but people have formed the habit of using the BLDC compressor for air conditioner is called DC inverter air conditioner.

Brushless DC motor

Brushless DC motor with AC motors or brush DC motor maximum difference is that the rotor is made from the rare-earth permanent magnetic materials, stator winding adopts margin set, simply speaking, it is a normal DC motor by permanent magnet rotor stator composed into the General needs of DC motor commutator and brush with the power of the stator coil winding rotor becomes. In this way, you can dispense with the need for General DC motors, and the brush properties of the speed control of DC motor, so the motor called brushless DC motor. Brushless DC motor which overcomes the traditional DC motor deficiencies, such as electromagnetic interference, noise, poor spark reliability, short service life, and have the AC motor does not have some advantages, such as running efficiency, speed of the performance is good, no Eddy current losses. Therefore, DC inverter air conditioner relative and Exchange inverter air conditioner, have more energy.

Rotor position detection

As a result of brushless DC motors at run time, you must immediately detect the location of the permanent magnet rotor, thus make the corresponding drive control for driving motor commutation, can guarantee the motor to run smoothly. Realization of brushless DC motor position detection there are typically two ways, one is the use of motor internal position sensor (usually a Hall element) of the signal; the second is to detect out-of-phase brushless DC motor, the use-phase of the sampled signal values obtained. Brushless DC motor has two phase coil power, any one phase is not receiving power. General cannot power on coil induction voltage measured, often remaining one phase as the rotor position detection signal cable, capture the induced voltage, through specially designed electronic control circuit switching, in turn, to impose a square-wave voltage stator coils; as the latter method dispense position sensors, DC inverter air conditioner compressor using the latter method for motor commutation.

DC inverter air conditioner and AC inverter air conditioner EFI difference

AC variable frequency inverter air conditioning in accordance with SPWM modulation method module, repulsive by triode, to power up-phase coil at the compressor, the compressor is a three-phase AC compressors.

DC inverter air conditioner frequency module every time on second transistor (A + and A-not breakover, B +, B-not breakover, C +, C-not on), two phase coil flux to DC, driven rotor spins another phase coil not power on, but the induced voltage, depending on the size of the induced voltage to determine the position of the rotor, thus controlling winding power on sequence. DC inverter AC variable frequency more than one location detection circuit.

DC inverter air conditioner can be divided into two categories, one category is only compressors using the BLDC motor; the second is not only compressors, also includes indoor and outdoor air blower fans are brushless DC motor, and refrigerant regulation by capillary into electronic expansion valve, this is the full DC inverter air conditioner.

III. frequency of the basic principles of air conditioning circuit

Overview:

Indoor circuit is basically the same as with normal air, only increase and machine communication circuit, through the signal line "S", according to certain rules of communication and outdoor machine communication, signal lines through the "S" to + 24V electrical signals.

The outdoor circuit is generally divided into three parts: outdoor main control board, outdoor power supply circuit, IPM frequency module components. Power circuit complete AC filter, protection, Rectifier, power factor adjustment, stable frequency modules provide DC power source. The main control board implementation of temperature, current, voltage, compressor overload protection, the protection of the detection module; press, fan control; to communicate with the indoor unit; calculation of six-phase drive signal, control inverter module. Inverter module components enter 310V DC voltage, and accept the main control board control signal, the power for the operation of the compressor provides.

1. a communication circuit

Traffic rule: from the host (indoor unit) send signals to the outdoor unit is in receipt of outdoor unit status signal processed 50 milliseconds after the same Deputy machine etc receive host (indoor unit) send signals processed 50 milliseconds after communication to indoor unit as primary, and normal host after waiting to receive the sent, such as 500 milliseconds have yet to receive the signal is then sent the current command, if the 1 minute (DC inverter is 1 minute, 2 minutes for AC variable frequency) does not receive each other's answer (or response error), then the error alarm; at the same time send information command to outdoor to outdoor machine to machine, the outdoor unit is not receiving a signal to the indoor unit, you have been waiting for, do not send a signal that the communication sequence as follows:

Circuit analysis

Because of the air-conditioner and the outdoor unit of distance farther, so two-chip communications (+ 5V signal) cannot be directly connected, the intermediate driver circuit must be increased to enhance the communication signal (to + 24V), resistance to outside interference.

Diode D1, resistor R1, R2, R47, capacitor C3, C4, Zener diode CW1 composition power circuit communication circuits, AC via D1 half wave rectifier, R1, R2-limiting R47 resistor split after the Zener diode CW1 will output voltage stability in 24V, C3, C4 filtering, as communication loop provides stable 24V voltage, the entire communication loop circulation around for 3mA.

Optical coupling IC1 and IC2, PC1, PC2, from isolation to prevent the distribution on the loop current, high voltage series into the chip inside, damaged chip, R3, R18, R21, R22 resistor current limiting, stable 24V voltage into the loop current 3mA, R23, R42 resistance, protect optical coupling, D2, D5 prevent reverse N, S.

When the communication is sent and outdoor reception room, outdoor TXD reset high powerSend a ping, outdoor optical coupling PC2 always breakover, to send a high level of indoor TXD "1", indoor send optical coupling IC2 breakover, communication loop closure, receiving Photocoupler IC1, PC1 breakover, outdoor RXD receive high level "1"; if low level indoor TXD send "0", indoor send optical coupling IC2, communication loop disconnect, receiving Photocoupler IC1, PC1, outdoor RXD receive low level "0", enabling communication signals from indoor to outdoor transmission. Similarly, analysis of communication signals from outside to inside of the transfer process.

2. AC power supply filtering and protection

The main function is to absorb the power grid all kinds of interference and inhibit electric controller itself on the power grid of electromagnetic crosstalk and over-voltage protection and lightning protection.

FS1-delay fuse, can prevent electronic control for a long time overcurrent or short circuit, at the same time, but also in the input voltage is too high, and with the protection of subsequent circuit ZMR1 against impact and millions of damage.

AS1, ZMR2 comprise lightning protection circuit.

C1, C4, C5, T1, C2 composition effective electromagnetic interference filters, the filter that has a two-way role can absorb power grid on electric controller, can prevent the harmonic electric controller itself into the power grid.

3. the part of the high-voltage DC power supply frequency converters

The part of the function is rectifier AC input filtering to 300V or high-voltage DC supply variable frequency drive part as the primary source of energy. And will have the current waveform distortion correction reduces the high time filtering (in odd-) on the power grid. And improves the power factor.

PTC1, consisting latency-instant RL3 current circuit to prevent the initial power-on capacitance of excessive current impact, so as not to insert the power plug, the spark plug and socket, if normal indoor and outdoor machine communication, delay of 3-5 seconds hand, RL3 pick-up.

Rectifier bridge heap DB1 AC rectifier to DC, the device may have a circuit breaker failures and short circuit, open circuit caused by the phenomenon is compressor starts, turning a stops producing under-voltage protection, short circuit can cause phenomenon is the user's insurance blowing or load shifting protector.

C81-C83 main filter capacitor, the capacitor is likely too breakdown, electrolyte dry and ambient temperature is too high may be susceptible to damage. Damage in two situations: failure (including circuit breaker) and short circuit, which features the same heap with Bridge, and circuit bridge pile of short circuit.

DB2, C26, L1 group success factor correction circuit, this portion of DB2 for the key points of failure, the device is fixed to the heat, the lead profile when the phenomenon with DB1 circuit, short circuit can be replaced, there is no obvious performance, only electrical interference, NetEase does not affect the use of frequency conversion air conditioning.

4. the inverter module

P, n-terminal access 300V high voltage DC, CZ Terminal from the main control board Department to control signal, control of six transistors switching to obtain accurate control voltage, U, V, W on compressor output control voltage, AC frequency output for three-phase AC, DC inverter output to power DC winding changing.

5. all DC fan motor

Indoor DC fan

Size by changing the voltage to control the fan speed, voltages in the range of Vc 9 ~ 36V, the higher the voltage, fan speed, the higher the voltage, the lower the lower fan speed; + 5V for the fan of the work of the internal control board;

Outdoor DC fan

Outdoor DC fan works and DC compressors are basically the same, just the PWM voltage waveform shaping circuit in the motor; Vc for high-voltage DC power supply section provides DC power for fan coil work around using, 300V, because users have high power supply voltage is low, thus actual Vc; + between the 200V-375V 15V voltage is within the Board's work of fan voltage; Vsp for fan speed control signal, outdoor master chip issued fan speed control signals for + 5V pulse digital signal, after digital/analog conversion circuit, converted to a maximum voltage of + 15V analog signal, that is, Vsp, control motor in circuit board to produce the PWM voltage waveform; wind speed feedback signal to 12 pulses/rotations, pulse amplitude + 15V, because the main control board chip working voltage of + 5V, and therefore need the power Board converting to + 5V signal, in order to supply external master chip to detect the fan speed.