Inverter repair

Domestic brands have a good reputation converter: Delta, Oerlikon (formerly Huifeng), the Senlan, Childress, INVT, Kymmene and so on. Boring ranking Powtran Teco continent brand: Pu passes, INVT, ten, regardless of their ranking Siemens ABB Yaskawa Vocon Hua Fuzhou Hiconics East Third Ring Hitachi Power Jiuzhou 1: The inverter output is PWM wave and contains relatively many higher harmonics. Frequency power sensor through the voltage and current signals inputted AC sampling, then the value of the input sampling frequency power analyzer via a transmission system with digital cable, optical fiber, digital input frequency power analyzer sample values ??of voltage and current conduct arithmetic, you can get the voltage rms, current rms, fundamental voltage and fundamental current harmonic voltage and harmonic current, active power, fundamental power, harmonic power and other parameters. 2: On the domestic market in terms of the pattern of the drive, the industry will be summed up as, common areas of the drive-funded enterprises accounted for more than 80% market share, competitive price led to a substantial decline in 10 years; high performance market is still dominated by foreign brands the future will become the main direction of domestic inverter business. It is the intelligent electrical R & D, production and sales of high-tech enterprises. Production inverter, motor soft starters and other manufacturers of industrial automation and control products used heavy-duty design, overload, starting and running with large capacity, and improve the automatic detection, protection and control performance, you can start and control any types of heavy load motor products have been widely used in all industrial drives metallurgy, mining, paper, chemicals, building materials, machinery, electricity, and building systems, etc. 3: Chinese inverter market to maintain 12-15% growth rate, at least for the next five years will be maintained over 10% growth rate. The Chinese market drive the installed capacity (power) growth rate is actually about 20%, is expected to at least 10 years, in order to drive the market saturation and maturity. Frequency inverter power analyzer power analyzer (5) 2 Works Editing Overview of the main circuit is to provide asynchronous motor VVVF power supply power conversion part, the main circuit of the inverter can be divided into two categories: voltage type is DC voltage source is converted to AC inverter, DC link capacitor filter is. Current type is the DC into AC current source inverter, the DC circuit filter inductor. It consists of three parts, the frequency power into DC power, "rectifier" absorb "the extensive use of flat wave rectifier circuit is a diode converter converter and the inverter generates a voltage ripple, it is the frequency power into DC power supply is also available in two transistor inverter constituted reversible flow, because of its power direction reversible, can be regenerated running. smoothing the DC voltage rectified by the rectifier circuit after the power supply contains 6 times frequency ripple voltage, ripple current generated by the inverter in addition also makes the DC voltage fluctuation. In order to suppress voltage fluctuations, the use of inductors and capacitors absorption pulsating voltage (current) capacity means hours, if the power supply and the main circuit device has a margin, omitted smoothing inductance circuit using a simple inverter with the rectifier contrary, the inverter is converted to DC power by the frequency of the AC power required to determine the time for the switching device 6 is turned off to You can get 3-phase AC output to the voltage-pwm inverter as an example shows the switching time and voltage waveforms to the asynchronous motor control circuit is powered (voltage, frequency adjustable) primary circuit provides a control signal circuit, it has a frequency, the control signal voltage "operation circuit", the main circuit "voltage, current detection circuit" motor "speed detection circuit", the operation circuit amplifying "driving circuit", and the inverter and the motor, "Protection Circuit "Composition (1) operation circuit: current, voltage signal is outside the speed, torque and other instruction are compared with the detection circuit operation decider inverter output voltage, frequency (2) the voltage, current detection circuit: and main circuit potential isolation detection voltage, current, etc. (3) driving circuit: drive the main circuit device and control circuit isolation circuit which the main circuit device is turned off (4) Speed ??detection circuit: with mounted induction motor speed detector (tg, plg, etc.) on the signal axis machine speed signal circuits into operation, the motor can according to an instruction by instruction and operation speeds (5) protection circuit: detection of the main circuit voltage, current, etc., When an overload or other abnormal over-voltage, in order to prevent damage to the inverter and asynchronous motors 3 Function Editor frequency energy saving drive mainly in the fan and pump applications. In order to ensure the reliability of production, a variety of production machinery When designing equipped with power-driven, have left certain amount of surplus. When the motor can not run at full load, in addition to achieve power-driven requirements, excess torque increases active power consumption, resulting in energy waste. fans, pumps The governor and other equipment traditional method is by adjusting the inlet or outlet baffles, the valve opening amount is adjusted to the wind and to the water, the input power, and a lot of energy consumed in the closure process baffle in the valve. When using When the frequency control, if the flow requirement is reduced by reducing the pump or fan speed to meet the requirements of the role of the motor inverter is to control, and reduce the starting current. In order to produce a variable voltage and frequency, the device AC power is first necessary to convert direct current (DC), this process is called rectification. The direct current (DC) is converted into alternating current (AC) means the scientific term for the "inverter" (inverter). General inverter is a DC power inverter to a certain fixed frequency and constant voltage of inverter. For the inverter frequency is adjustable, adjustable voltage inverter drive we called. Inverter output waveform is an analog sine wave, is mainly used in three-phase induction motor speed control with, also known as the inverter. The main instrument for use in testing equipment waveforms higher variable frequency inverter, waveform want to organize, you can output standard sine wave, called frequency power. The general frequency inverter power source is 15 - 20 times the price. Since the main means changing voltage or frequency converter device called generation "inverter", so the product itself was named "inverter", namely: drive. Not everywhere you can power inverter, there are many occasions with frequency does not necessarily power. As an electronic circuit, the drive itself, but also power consumption (approximately 3-5% of rated power). A 1.5 air-conditioning is also doing its own power 20-30W, the equivalent of a long light. Drive runs at power frequency, with power-saving features, is a fact. But his preconditions: first, high-power and for the fan / pump load; second, the device itself has a power saving function (software support); this is a manifestation of energy-saving effect of the three conditions. In addition, energy-saving section does not matter, it does not make sense. If not a prerequisite that the inverter frequency operation of energy-saving, is exaggerated or commercial speculation. Know the whole story, you'll clever use him for your service. Be sure to pay attention to use the occasion to do the correct application and use, or is blind obedience, credulity and "deceived." Saving power factor compensation of reactive power line not only increase the heat loss and equipment, but the main thing is to reduce the power factor leading to lower active power grid, the large amount of reactive power consumption in which the line, the device uses inefficient, wasteful use After the frequency control devices, the role of the inverter internal filter capacitor, thereby reducing the reactive power loss, increasing the active grid. Soft start saving 1: Motor hard start serious impact on the grid, but also on the grid capacity is too high, damage to the baffle and the valve when a large current and vibration generated when the start is great, the equipment and pipelines life is extremely unfavorable. After the use of variable frequency energy-saving devices, use the drive current soft-start function will start from scratch, do not exceed the maximum rated current, reducing the impact on power and power capacity requirements, to extend the use of equipment and valves life. Saving equipment maintenance costs. 2: In theory, the drive can be used in all mechanical equipment with a motor, when the motor starts, will be higher than the rated current of 5-6 times, not only will affect the life of the motor and consumes more power The system was designed on the motor selection will leave a margin, the speed of the motor is fixed, but in actual use, sometimes you want to run at a lower or higher speed, frequency transformation is therefore very necessary. The drive can achieve motor soft start, power factor compensation 4 basic components to edit the drive is usually divided into four parts: the rectifier unit, high-capacity capacitors, inverters and controllers. Rectifier unit: The fixed frequency alternating current is converted to direct current. High capacitance: a converted power storage. Inverter: the high-power switching transistor array composed of electronic switches, the direct current is converted to a different frequency, the width, the amplitude of the square wave. Controller: work according to set procedures, controlling the amplitude and pulse width square wave output, making an approximate sine wave superimposed AC, AC motor drive. 5 Given edit inverter common frequency for a given mode are: the operator keypad reference, contact signal is given, the analog signal is given, the pulse signal given and given and other means of communication. These methods have advantages and disadvantages of a given frequency shall be selected in accordance with the actual requirements set 6 Related Q & A Edit Inverter is the use of power semiconductor devices will be the role of the on-off frequency to another frequency power conversion power control device that can realization of AC induction motor soft starters, frequency control, improve running accuracy, changing the power factor, overcurrent / overvoltage / overload protection and other functions. Different points PWM PWM and PAM is English Pulse Width Modulation (pulse width modulation) acronym, according to certain rules changing the pulse width of the pulse train to regulate a modulation output and waveform. PAM is English Pulse Amplitude Modulation (pulse amplitude modulation) acronym is based on certain rules to change the pulse amplitude of the pulse train to adjust the output value and a modulation waveform. 3, the voltage and current - What is the difference? The main circuit of the inverter can be divided into two categories: voltage-source DC voltage is converted to AC inverter, DC circuit filter is a capacitive; current mode is the DC into AC current source inverter, dc loop filter inductor. 4, Why voltage proportional to the frequency change in the drive? Any electromagnetic torque of the motor is the result of the interaction of current and flux, current is allowed to exceed the rated value, otherwise it will cause heating of the motor. Therefore, if the magnetic flux is reduced, the electromagnetic torque shall be reduced, resulting in reduced load capacity. By the formula E = 4.44 * K * F * N * Φ can be seen in the inverter, the motor's magnetic circuit with the operating frequency fX is varied within a large range, it is very easy to make a serious motor magnetic circuit saturation, resulting in severe excitation current waveform distortion, resulting in high peak current spikes. Therefore, the frequency and voltage is proportional to change, that change while the control frequency inverter output voltage, so that the motor flux to maintain a certain, to avoid weakening and magnetic saturation phenomenon. This control method is used for fans, pumps and energy-saving drive. 5, when the motor is driven using the power frequency, voltage drops the current increases; for inverter drive, if the frequency decreases voltage drop, then the current is increased? Decreased frequency (low speed), if the same power output, the current increases, but under certain conditions the torque, current is almost constant. 6, when using the inverter operation, the motor starting current, starting torque what? The use of inverter operation, with the acceleration of the motor corresponding increase in the frequency and voltage, the starting current is limited to 150% of rated current (depending on different models, 125% to 200%). Labor frequency power directly start, the starting current is 6 to 7 times the rated current, therefore, will have an impact on electrical machinery. Using inverter drives can smooth start (start time becomes longer). Starting current of 1.2 to 1.5 times the rated current, starting torque of 70% to 120% rated torque; for with a torque converter automatic enhancement features, starting torque of 100% or more, you can start with a full load. 7, V / f pattern mean? When the frequency is proportional to the voltage drop V also declined, this question has been answered 4 instructions. The ratio between V and f are considered motor characteristic determined in advance, usually there are several properties in the controller of the storage device (ROM), you can use a switch or dial to select. 8, according to the proportion of the land reform V and f, motor torque change? Completely reduced proportionally decreased frequency voltage, since the impedance becomes small DC resistance unchanged, will result in a tendency to produce a reduced torque at low speed there. Thus, at low frequencies given V / f, the output voltage is increased to make the number, in order to obtain a certain way starting torque, such compensation starting said enhanced. You can use a variety of ways, there are ways to automatically, select V / f mode or adjust potentiometers, and other methods. 9, written in the manual speed range 60 ~ 6Hz, namely 10: 1, then the following 6Hz output power not it? In the 6Hz still less output power, but according to the starting torque of the motor temperature and size and other conditions, the lowest frequency of use take about 6Hz, this time the motor output rated torque without causing serious heating problems. Actual inverter output frequency (starting frequency) according to models of 0.5 ~ 3Hz. . 10, for a combination of general motors is also required above 60Hz torque constant, can we? Normally when not. Above 60Hz (there are more than 50Hz mode) voltage constant, substantially constant power characteristics at high speeds require the same torque 11, the so-called open-loop What does it mean? Motor means used to set the speed detector (PG), the actual speed feedback to the control means controls, called "closed loop", without PG functioning on called "open loop." Drive more common open-loop mode, and some models can take advantage of optional PG feedback speed sensorless closed-loop control mode is based on the mathematical model of the flux calculated according to the actual speed of the motor, the equivalent of using a virtual speed sensor forming a closed loop control. 12, the actual speed for a given speed deviation how to do? Open-loop, the inverter output if a given frequency, the motor is running with load, the motor speed in the range of the rated slip (1% to 5%) change. For high speed accuracy requirements, even if the load changes also require nearly the speed of operation of a given case, the drive can be used with a PG feedback function (optional part). 13, if a motor with PG, the feedback speed precision can be improved after it? Inverter with PG feedback function, accuracy is improved. But the value of speed accuracy depends PG own accuracy and resolution of the output frequency. 14 Stall prevention What does it mean? If a given acceleration time is too short, the output frequency of the inverter is far more than the speed (electric angular frequency) changes, the inverter will vary the current flowing through the trips run stop, which is called stall. In order to prevent stalling the motor continues to run, it is necessary detection current size frequency control. When the acceleration current is too large due to slow accelerating rate. The same is true when you slow down. Combining the two is the stall function. 15, there is acceleration time and deceleration time can be given aircraft, and ramp time together given aircraft respectively, what's the point? Acceleration and deceleration of the aircraft can be given, for quick acceleration, Deceleration respectively occasions, or for small machine requires strict tact time given occasion is appropriate, but for the fan drive and so on, acceleration and deceleration time is longer, Acceleration and deceleration times can be given together. 16, what is regenerative braking? If the motor is in operation reduces the command frequency, the motor becomes asynchronous generator running status, and work as a brake, which is called regenerative (electric) braking. 17, whether to get greater braking force? Renewable energy from the motor out of the filter capacitor piling up in the drive, since the relationship between the capacitance of the capacitor and the voltage of the regenerative braking force general inverter rated torque of about 10% to 20%. Such as the use of optional part brake unit, it can reach 50% to 100%. 18, please indicate the protection function of the inverter protection function can be divided into the following categories:? (1) The detector automatically performs the correction operation after an abnormal state, such as over-current stall prevention, regenerative overvoltage stall prevention. (2) detecting power semiconductor devices PWM control signal abnormal blockade, the motor automatically stop. Such as over-current cut-off, regenerative overvoltage cut semiconductor cooling fan overheating and instantaneous power failure protection. 19, why the load is connected with the clutch protection function of the inverter on the action? When the load is connected with the clutch, dramatic changes in an instant, the motor idling state to slip from a large area connections, resulting in a large current flows through the inverter overcurrent trip, it can not operate. 20, in the same factory move large motors together, running in the drive to stop, this is why? The flow through the motor when starting and capacity corresponding to the starting current, the motor stator side transformer voltage drop, high motor capacity when this drop impact is large, connected to the same transformer drive will make voltage or instantaneous stop The judgment, which sometimes protection (IPE) action, causing stopped. 21. What is the frequency resolution? What is the significance? For the digital control of the drive, even if the frequency command is the analog signal, the output frequency is also a given level. The smallest unit is called the differential frequency resolution. Frequency resolution is typically a value of 0.015 ~ 0.5Hz. For example, with a resolution of 0.5Hz, then the above 23Hz may become 23.5,24.0 Hz, therefore the operation of the motor is also a stage to follow. Such as continuous winding for control purposes has caused problems. In this case, if the resolution is about 0.015Hz, for four motor a differential of 1r / min or less, and can be fully adapted. In addition, some types of aircraft given resolution and the output resolution is not the same. 22. Are there restrictions on the mounting direction when installed drive. Inside and back of the drive structure to consider the cooling effect, the relationship between the upper and lower ventilation is also important, therefore, to the inner cell type in the tray, hanging on the wall are taken longitudinal position, as vertically. 23 Can not use soft start the motor directly into a fixed frequency converter? At very low frequencies it is possible, but if given the same frequency of the high frequency power directly start conditions similar. The flow through the large starting current (6 to 7 times the rated current), because the frequency cut off the overcurrent, the motor does not start. 24, when the motor over 60Hz operation pay attention to what the problem? More than 60Hz operation should note the following: (1) machinery and equipment operating at the speed may be sufficient (mechanical strength, noise, vibration, etc.). (2) Motor enters constant power output range, the output torque to be able to sustain operation (fans, pumps and other shaft output power increases proportional to the cube of the speed, so we should pay attention when a little speed increase). (3) produce the bearing life issues should be fully taken into account. (4) the capacity for more than 2-pole motor motor especially when running at 60Hz and above should be carefully discussed with the manufacturers. Depending on the structure and lubrication gear, you need to pay attention to several issues. Gear in the structure can generally be considered 70 ~ 80Hz maximum limit, when oil lubrication, continuous operation at low speed related to gear damage and the like. 26, the drive can be used to drive a single-phase motor it? You can use a single-phase power supply? Basically unusable. For the governor switch start type of single-phase motors, in the speed range below the operating point of the auxiliary winding will burn; for capacitor start or capacitor run way will induce capacitor explosion. Inverter 3-phase power supply is usually, but for small capacity, but also useful models of single-phase power supply operation. 27, the drive itself how much power consumed? It inverter models, operating status, frequency of use and so on, but very difficult to answer. However, the efficiency of 60Hz or less the inverter approximately 94% to 96%, whereby the loss can be estimated, but built-in regenerative braking style (FR-K) drives, if the loss is taken into account when braking, power consumption The bigger, the operation panel design must pay attention to. 28, why not 6 ~ 60Hz continuous operation throughout the region to use? General motors use outer fan mounted on the shaft or the rotor end ring blade cooling, if the speed decreases the cooling effect is reduced, and therefore can not afford the same heat and high-speed operation, the load must be reduced torque at low speeds, or use large capacity inverter and motor combination, or the use of special motor. 29. What is the use of a motor with brake should pay attention to? Brake excitation circuit power should be taken from the input side of the inverter. If the drive is being output power when the brake is actuated to cause over-current cut off. So to make the brakes stop the inverter output before action. 30, would like to use the drive with a drive to improve the power factor correction capacitor motor, motor did not move, please explain why. The drive current flows into the power factor correction capacitors, due to the charging current causes the inverter overcurrent (OCT), so we can not start, as a countermeasure, connect the capacitor after the removal operation, as to improve the power factor, the input side of the inverter Access AC reactor is effective. 31, the drive has a long life? Although the static inverter device, but it does have a filter capacitor, the device consumes as cooling fans, if they carry out regular maintenance, is expected to have more than 10 years of life. 32, the inverter's internal cooling fan, wind direction? What happens if the fan is broken? For small capacity but also whether the cooling fan of the aircraft. A fan of the aircraft, the wind direction is from the bottom up, so the installation of the drive where the upper and lower do not put impede suction and discharge of machinery and equipment. Also, do not place the top of the drive span of parts. When a fan fails, the fan stops detecting or overheating detection protection on the cooling fan 33, a filter capacitor for the consumables, then how to judge its life? Filter capacitor used as a capacitor, whose capacitance with time and gradually reduced, the electrostatic capacitance measured regularly, in order to achieve 85% of the rated capacity of the product as a benchmark to judge the life time. 34. Are there restrictions on the mounting direction when installed drive. Should be substantially housed in the tray, the problem is the use of large fully enclosed structure of the disk size, space, the cost is relatively high. Its measures are: (1) The disc is designed to be practical means for cooling needs; (2) the use of aluminum heat sinks, cooling fins increase the cooling area and the like; 35, what is the role of the inverter DC reactor is? Reduce the input current harmonic interference and improve the input power factor. 36, drive accessory sine filter for? Sine filter allows drive long motor cable runs, also applies between the inverter and the motor intermediate transformer circuit. 37, the drive given potentiometer resistance value be? Given potentiometer resistance converter is generally 1KΩ to 10KΩ. 38, why the drive can not be used as variable frequency power supply? The entire circuit frequency power by an AC AC DC and other parts of a filter, the voltage and current waveforms that are pure sine wave output, very close to the ideal of the AC power supply. You can output the grid voltage and frequency of any country in the world. The inverter is a DC by the AC AC (modulated wave), and other circuits, the drive should be called standard inverter. Its output voltage waveform is a square wave pulse, and more harmonic components, voltage and frequency at the same time in proportion to changes in non-adjusted, does not meet the requirements of the AC power supply. In principle, it does use the power supply, generally used only for three-phase induction motor speed. 39, the inverter which disturbances and generally how to deal with? Spread: (1) radiation interference; (2) Conducted interference immunity measures: for interference signal propagation by radiation methods, mainly through the wiring and the sources and interference shielding line way to weaken. For the interference signal propagating through the line, primarily to deal with through the inverter input and output side of the installation filter reactor or magnetic and other ways. Specific methods and precautions are as follows: (1) signal line and the power line is to be perpendicular cross or slotted wiring. (2) Do not use wires of different metals are interconnected. (3) shield tube (layer) should be grounded, and to ensure continuous reliable ground over the entire length. (4) The signal circuits to be used in shielded twisted-pair cable. (5) Shield ground point away from the inverter, and is separate from the inverter ground. (6) The ring can be entered in the drive power lines and output lines using the specific method is: the input line together in the same direction around four laps, while the output line in the same direction to three laps around. Winding takes note, try to ring near the inverter. (7) The equipment and the equipment generally is disturbed, can take the shield and other anti-jamming measures. 40, want to improve the existing conveyor speed to 80Hz operation, the capacity of the drive how to choose? Power consumption and speed is proportional to the belt, so if you want to run 80HZ, power inverter and the motor must be in proportion to the increase of 80HZ / 50HZ, namely by 60% of capacity. 41. What is the difference between using the PWM and VVC + is? In VVC the control circuit to use a mathematical model to calculate the optimal motor excitation of the motor load changes, and compensate the load. Also integrated in the synchronous 60 ° PWM method ASIC circuit determines the inverter semiconductor device (IGBTS) optimal switching time. We decided to switch the time to follow the following principles: 1. The maximum value of a phase to maintain its positive potential within 1/6 cycle (60 °) or a negative potential unchanged. 2. The other two phases vary in proportion to the output line voltage is maintained sinusoidal and reaches the desired amplitude. Different sinusoidal PWM control, VVC is based on the digital output voltage to the required work. This ensures that the inverter output voltage reaches the rated value, the motor current is a sine wave, as the motor is running and the motor connected directly to electricity. Because when calculating the optimum output voltage of the inverter into account the constant of the motor (stator resistance and inductance), so get a best motor excitation. Because the drive is continuously detecting the load current, the inverter output voltage can be adjusted to match the load, so the motor voltage can be adapted to the type of motor, follow the changes in the load. 7 Edit the low-pressure common frequency control output voltage 380 ~ 650V, output power is 0.75 ~ 400kW, operating frequency is 0 ~ 400Hz, its main circuits using AC - DC - AC circuits. Its control through the following four generations. The first generation 1U / f = C sinusoidal pulse width modulation (SPWM) control: the control circuit is characterized by simple structure, low cost, mechanical properties of hardness are better able to meet the general requirements of smooth speed transmission, it has been in all areas of the industry are widely used. However, this control mode at low frequencies, due to lower output voltage, torque stator resistance voltage drop is affected by more significant, so that the maximum torque output decreases. In addition, the mechanical properties of hard after all there is no DC motors, dynamic torque capacity and static speed performance are not satisfactory, and the system performance is not high, the control curve will change with load changes, the torque response is slow, the motor turn Moments utilization rate is not high, low speed due to the presence of the stator resistance and inverter dead effects and performance degradation, poor stability and so on. So people would come up with Vector Control. The second generation of the voltage space vector (SVPWM) control: It is three-phase waveforms generated overall effect as a precondition to approximate the ideal circular locus motor rotating magnetic field gap for the purpose of generating the first three-phase modulation waveform, endo polygonal approximation controlling the way round. The practice has improved after use, namely the introduction of frequency compensation, can eliminate the error rate control; flux amplitude estimate through the feedback, to eliminate the influence of stator resistance at low speeds; the output voltage, current loop, in order to improve accuracy and dynamic stability. However, many aspects of the control circuit, and without introducing torque adjustment, the system performance has not been fundamentally improved. Third Generation Vector Control (VC) mode: Vector Control approach is three-phase asynchronous motor stator current coordinate system Ia, Ib, Ic, by a three-phase - two-phase conversion, equivalent to a two-phase stationary Coordinates alternating current Ia1Ib1, then by rotating rotor flux oriented transformation into a direct current Im1 equivalent synchronous rotating coordinate system, It1 (Im1 equivalent DC motor excitation current; It1 equivalent proportional torque armature current), then imitate the DC motor control method, seek to control the amount of DC motor via the corresponding coordinate inverse transform, to achieve the asynchronous motor control. Its essence is the equivalent AC motor DC motor speed respectively, independent control of the two components of the magnetic field. By controlling the rotor flux and the stator current decomposed to obtain torque and magnetic fields of the two components, the coordinate transformation, achieve orthogonal or decoupling control. Proposed vector control method of epoch-making significance. However, in practice, since the rotor flux it is difficult to accurately observing system greatly influenced by the characteristics of the motor parameters and the equivalent DC motor control used in the process is more complex vector rotation transformation, so that the actual effect is difficult to achieve the desired control analysis Results. The fourth-generation direct torque control (DTC) mode: In 1985, Germany's Ruhr University professor DePenbrock first proposed direct torque control inverter technology. This technology largely solves the problem of the above-mentioned vector control, and control to new ideas, concise system architecture, excellent static and dynamic performance has been developing rapidly. The technology has been successfully applied on electric locomotive traction power AC drive. Direct Torque Control of mathematical model of AC motors directly in the stator coordinate system, control motor flux and torque. It does not require the equivalent AC motor DC motor, thus eliminating many complex calculations vector rotation transformation; it does not need to imitate the DC motor control, no need for the decoupling and simplified mathematical model of AC motor. Matrix AC - AC control mode: VVVF inverter, variable frequency vector control, direct torque control frequency are AC - DC - AC converter in one. Their common drawback is the low input power factor, harmonic current, the DC circuit requires a large energy storage capacitors, renewable energy and can not be returned back to the grid, that can not be four-quadrant operation. To this end, Matrix AC - AC converter came into being. Since Matrix AC - AC converter eliminates the intermediate DC link, thereby eliminating the need for bulky, expensive electrolytic capacitors. It can achieve power factor of l, the input current is sinusoidal capable of four-quadrant operation, high power density of the system. Although the technology is not yet mature, but still attracted many scholars studied. Its essence is not indirectly control current, flux equal, but the torque is controlled directly as an amount to achieve. The specific method is: 1, control stator flux introduced stator flux observer, speed sensor-free manner; 2, automatic identification (ID) rely on accurate motor mathematical model, automatic identification of motor parameters; 3, calculates the actual value corresponds to the stator impedance, mutual inductance, magnetic saturation factor, inertia and other calculated actual torque, stator flux, the rotor speed real-time control; 4, to achieve Band-Band control PWM signal generated by the flux and torque of Band-Band control, inverse Variable switch state control. Matrix AC - AC converter with fast torque response (