Wednesday, January 5, 2011

【 Weak current College 】 inverter air conditioner control circuit theory and repair 】

A preamble at the beginning of the new century, household inverter air conditioner to the people of the family, in order to correct use, maintenance and repair of air conditioners, understand and master inverter air conditioner in principle, the main parts of the structure and maintenance technology, become a top priority, inverter air conditioner air conditioner than constant speed control circuit complexity, it introduced many protection circuit, the circuit uses a different sensor technologies, such as frequency module, the Hall element, optical Coupler, watchdog circuit, switching power supply circuit, etc. Based on the theory and practical maintenance practice, this article detailed analysis of the air conditioner control circuit and maintenance technology, for promotion and popularization of inverter technology to better meet the growing material and cultural needs, is important. Second air conditioner control circuit analysis inverter air conditioner is developing direction of room air conditioners, it passed variable frequency controllers regulate compressor speed (frequency), the amount of cooling (heat) and room thermal (cold) load automatically match with thermostat speed, maintenance of low-temperature thermal efficiency, high control precision, suitable temperature and voltage range, etc. Especially with the frequency conversion technology, air-condition from AC frequency go to DC Brushless motor, permanent magnet synchronous motor with frequency converter, inverter air conditioner either from the use of power electronic devices or control policies are widely used in modern advanced technology. Whether domestic or imported inverter air conditioner, its control circuit in much the same, the General indoor and outdoor machine control circuit. Inverter air conditioner of indoor and outdoor machine can communicate with each other, and were the two single-chip control. The entire system of control charts as well as the role of the various links as shown in Figure 1. The entire control system consists of intelligent power module IPM, power plate, Interior panels, switch boards, outdoor main control board and inverter compressor, and several major components. The entire system of the controlled object is a variable-frequency compressor, compared with constant speed air conditioners, inverter air conditioner use power supply frequency is adjustable, so it has high efficiency and energy saving, low temperature fluctuation, small, comfort and high operating voltage range, sensor control precision, low run-time adaptability, good independent dehumidification functions fine performance, frequency compressors using AC induction motor, synchronous motor (PMSM) or switch reluctance motor; intelligent power module IPM uses six packaging or seven package GTO, IGBT, power electronic devices, and overcurrent, undervoltage, overtemperature protection, GTO or IGBT driver circuit integrated in one; the power Board is will power through bridge rectifier, filter, regulator and later get DC current supply IPM, inverter output frequency variable three-phase alternating current supply frequency compressors; indoor and outdoor main Control Board is the soul of the whole system and core, using two-chip, with the development of science and technology, the controller is now widely used for digital signal processor (DSP) to handle a variety of input signal of the directive (such as room temperature) and the feedback signals (such as the actual room temperature), make the control more accurate and reliable, this inverter air conditioner, it was known as the "digital inverter air conditioner". Outdoor master plate complete frequency conversion control of three-phase power supply, resulting in a six-Lu algorithm PWM waveform driven IPM in the on/off, power electronic devices at the same time as the outdoor environment temperature detection, condenser temperature detection, exhaust temperature detection, AC voltage, AC current, and complete the protection, processing and communication capabilities; indoor Board for indoor fan, room temperature detection, evaporator temperature detection, indoor and outdoor communication, wind/air control, complete remote control reception, LCD drivers for buzzer-machine conversation. Three fault repair technology in the process of inverter air conditioner use is inevitably fails, when problems occur, to timely repair, here are some common maintenance skills. 3.1 symptom and judging (1) plug in the power plug, the power led is lit indoor unit, such as have no power indicates that your family's power supply has failed or instructions and other damage. (2) the power, with the remote control press the action key, signal transmission does not go out. First, check whether the batteries in the remote control have power, and then check the battery polarity tablets-contact any corrosive, above normal, check the remote control for the internal circuit is damaged, you can set the remote control near one of am radio, press the key to listen to the radio interference test, whether or not to issue a "beep" sound, audio description of remote control without fault. (3) when the remote control to determine if no failure, no signal or emission, available when you go out indoor forcing the running switch, compulsory at run time, the Interior cross flow fans and outdoor compressor if working properly, the refrigeration effect is good, then prove that air conditioner indoor infrared receiving parts of a failure. (4) when you use remote control with new batteries use a month is not displayed, you can open the rear door of the remote control, with 95% ethanol wash circuit board and press the contact surface conductive film, drying, you can exclude leakage failure, remote control, LCD-display missing characters can also be used in this way. (5) in the inverter air conditioner temperature sensor plays a very important role in indoor air temperature sensor and evaporator temperature sensor; outdoor air temperature sensor, pressure sensor and low pressure line pipe sensor, sensor occurs after the long-term use of the resistance of the change, and make control characteristics, (such as indoor air temperature sensor resistance grows, will cause the inverter output frequency too low), in order to ensure accuracy, and control the same work characteristics, identify the sensor failure should swap the original type of the product. (6) in the air conditioning failure, if the identification of the entire control system is faulty, indoor unit controller switch is placed in a "trial run" block, you will be issued to the transducer MPU one frequency is 50 Hz signal, if this air conditioner can operate, and maintain frequency unchanged work, generally considered the entire control system no big problem, you can focus on the check all sensors are intact. If the air conditioner is not working, explains control system failure. 3.2 control system detection (1) communication circuit detects a communication failure, using a multimeter 250V AC voltage rail testing, in the zero line and the signal line if there is a voltage changes back and forth and indoor communication indicates, blinking, communication, communication circuits normally have failed.(2) power module detects power module failure, the first method is using a multimeter diode power modules, stalls measurement "+" very and U, V, W, or U, V, W and "-" pole-forward resistance of about 166 for 380-450 Ω, and reverse out conduction, otherwise the power module is at fault; the second approach is to use multimeter measurement of AC voltage, power module-driven compressor for voltage, the voltage of any two phases should be between 0 ~ 160V and are equal, otherwise the power module is damaged. (3) reactor in testing reactor, multimeter measure R X1 stalls, its winding resistance value of about 1 Ω. (4) when it detects the compressor, the compressor with a pair of pliers to unplug the U, V, W wire, three-phase voltage measurement, if the same three-phase voltage, compressor, compressor winding good winding fault. (5) Electrolytic Capacitor inverter air conditioner in the bulk of electrolytic capacitors, the maximum is 2000-4500uF, even if cut off power supply will still charge remained a charging, so for electrolytic capacitors to be used for soldering iron, plugs, and other objects fully release residual charge. Charge on all analog multimeter after using RX10K stalls detection, pointer should refer to 0, and then slowly return to ∞, electrolytic capacitors is damaged. (6) sensor frequency if the air conditioner to lifting and protective shutdown and other failures, you should first consider checking sensor, most of the sensors can disconnect from the outlet, from the appearance that you can determine whether damages, faults, retting. Hand or warm water heating, multimeter measuring its resistance RX100 stalls, whether it's resistance to change, no changes can be found the sensor is damaged. 4 closing this analysis of inverter air conditioner control circuit of the basic principles and common fault detection method for users or technicians repair has important reference value, a quick way for other pending further study and discussion of us.

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