Yaskawa Fuji low-voltage inverter | general-purpose inverter | wind pump dedicated | elevator dedicated |
Yaskawa Fuji low voltage inverter:
Voltage space vector (SVPWM) is premised on the overall effect of three-phase waveform generation. For the purpose of approximating the ideal circular rotating magnetic field trajectory of the air gap of the motor, a three-phase modulation waveform is generated at a time, and is controlled in such a way that the inward polygon approaches the circle. . After being used in practice, it has been improved, that is, the introduction of frequency compensation can eliminate the error of speed control; through estimating the amplitude of magnetic flux through feedback, eliminating the influence of stator resistance at low speed; and closing the output voltage and current to improve the dynamic accuracy and stability. However, there are many control circuits and no adjustment of torque is introduced. Therefore, the system performance has not been fundamentally improved. Since many domestic inverters still have a certain gap with foreign brands in vector control, the SVPWM control mode is more common in domestic inverter vector control modes.
The vector control frequency conversion speed regulation method is that the asynchronous motor in the three-phase coordinate system stator current Ia, Ib, Ic, through the three-phase-two-phase transformation, equivalent to two-phase static coordinate system under the alternating current Ia1Ib1, and then through According to the rotational orientation of the rotor field, the DC current Im1, It1 (Im1 corresponds to the excitation current of the DC motor; It1 corresponds to the armature current proportional to the torque) in the synchronous rotating coordinate system, and then imitates the DC motor The control method obtains the control quantity of the direct current motor and realizes the control of the asynchronous motor through the corresponding coordinate inverse transformation. The essence of this is that the AC motor is equivalent to a DC motor, which independently controls the speed and magnetic components. By controlling the rotor flux linkage, and then decomposing the stator current to obtain two components of torque and magnetic field, the orthogonal or decoupled control is achieved through coordinate transformation. Using vector control, the motor can be at low speed, such as (without speed sensor) 1Hz (for 4-pole motors, its speed is about 30r/min) can reach the output torque of the motor at 50Hz (about 150% of rated torque). For the conventional V/F control, the voltage drop of the motor is relatively increased as the motor speed decreases, which results in the motor being unable to obtain sufficient rotational force due to insufficient excitation. In order to compensate for this deficiency, the inverter needs to increase the voltage to compensate for the voltage drop caused by the reduced motor speed. This function is the torque boost. The torque boost function increases the output voltage of the inverter. However, even if a lot of output voltage is increased, the motor torque cannot be increased corresponding to its current. Because the motor current contains the motor generated torque component and other components (such as excitation components). Vector control assigns the motor's current value to determine the value of the motor current component and other current components (such as the excitation component) that produce the torque. The vector control can be optimized and compensated by the response to the voltage drop at the motor end, allowing the motor to produce large torque without increasing the current. This function is also effective for improving the temperature rise of the motor at low speed. The vector control method has also become an important advantage for foreign brands to occupy the high-end market.
Direct Torque Control (DTC) Method This technique has largely solved the above-mentioned deficiencies of vector control, and has been rapidly developed with novel control concepts, concise and clear system architecture, and excellent dynamic and static performance. At present, this technology has been successfully applied to high-power AC drives for traction of electric locomotives. Direct torque control directly analyzes the mathematical model of the AC motor in the stator coordinate system and controls the flux linkage and torque of the motor. It does not require that the AC motor be equivalent to a DC motor, thus eliminating many of the complex calculations in the vector rotation transformation; it does not need to mimic the control of a DC motor, nor does it need to simplify the mathematical model of the AC motor for decoupling. ABB's ACS800 series uses this type of control.
Matrix-type AC-ACV control method VVVF frequency conversion, vector control frequency conversion, direct torque control frequency conversion is a kind of AC-DC-AC frequency conversion. The common disadvantages are the low input power factor, large harmonic currents, large energy storage capacitors required in the DC circuit, and the inability to feed back the energy back to the grid, which means that four-quadrant operation is not possible. For this reason, matrix-type AC-AC frequency conversion came into being. Because the matrix-type AC-AC frequency conversion eliminates the intermediate DC link, it eliminates the need for bulky, expensive electrolytic capacitors. It can achieve a power factor of l, input current is sinusoidal and can operate in four quadrants, and the power density of the system is large. This technology is not yet mature. Its essence is not to indirectly control the current and flux linkage, but to directly use the torque as the controlled variable. Matrix-AC-AC frequency conversion has a fast torque response (<2ms), high speed accuracy (±2%, no PG feedback), high torque accuracy (<+3%); also has a higher start Torque and high torque accuracy, especially at low speed (including 0 speed), can output 150% to 200% torque. Low-voltage inverter - energy-saving principle of energy-saving inverter
Inverter energy saving is mainly reflected in the application of fans and pumps. In order to ensure the reliability of production, all kinds of production machinery are left with a certain margin when designing and using power drives. When the motor cannot be operated at full load, the excess torque increases the consumption of active power in addition to the power drive requirements, resulting in a waste of electrical energy. The conventional speed regulation method for fans, pumps and other equipment is to adjust the amount of air supply and water supply by adjusting the baffle and valve opening of the inlet or outlet. The input power is large, and a large amount of energy is consumed in the closure process of baffles and valves. in. When using variable frequency speed regulation, if the flow requirements are reduced, the requirements can be met by reducing the pump or fan speed.
According to fluid mechanics, P (power) = Q (flow) × H (pressure). The flow Q is proportional to the primary speed of the speed N, the pressure H is proportional to the square of the speed N, and the power P is proportional to the cube of the speed N. If the efficiency of the pump is constant, when the flow rate needs to be adjusted to decrease, the speed N can decrease proportionally, and at this time, the output power P of the shaft decreases. That is, the relationship between the power consumption of the water pump motor and the rotational speed is approximately established. When the required flow rate Q of the team is reduced, the inverter output frequency can be adjusted so that the motor speed n is reduced proportionally. At this time, the power P of the motor will be greatly reduced according to the relationship of the third power, saving 40% to 50% of the power of the baffle and the valve, thereby achieving the purpose of saving electricity.
Shenzhen Yangchen Automation Technology Co., Ltd.
Our technical maintenance department has strong technical force and rich maintenance experience. It can carry out inspection and repair of imported brands such as Mitsubishi, ABB, Yaskawa, Fuji, and other domestic brands.
Main Mitsubishi brand, ABB brand, Yasukawa brand, Fuji brand: Inverter, programmable controller (PLC), human-machine interface (HMI), servo system; ABB DC governor, large motor.
Yaskawa Fuji low-voltage inverter | general-purpose inverter | engineering inverter | wind pump dedicated | elevator dedicated | textile machinery dedicated | injection molding
The inverter in the inverter cabinet itself has no fault, but the external control circuit system has failed. Due to the long service life and the complicated control circuit, there is neither a circuit diagram nor a line number. The circuit is complicated and complicated, causing inconvenience to maintenance. Bad heat dissipation
The design of the frequency conversion cabinet is irrational, the internal is too narrow, and the heat dissipation and ventilation effect is poor, resulting in poor heat dissipation. Some frequency converters have a rather harsh working environment, with agglomeration of sand and dust, which seriously affects the normal operation of the inverter and even causes shutdown failures. The frequency conversion cabinet heat dissipation diversion fan is a consumable part, and the service life is generally about 2 years. However, after most of the frequency conversion cabinet cooling fan is damaged, it is not replaced in time, resulting in poor heat dissipation, causing the inverter to have poor working stability, aging deterioration, and frequent overheating alarms. And so on. Routine maintenance work can not keep up
Inverter's daily maintenance can not keep up. The operator did not understand the basic operation of the inverter and some basic parameter settings, and could not find the problem in time during use. "Little Marathon Car" problem
"Little Marathon" problem. Due to the limitation of the working conditions at the time of designing, the time required for designing and installing was to save money. In many places, variable frequency power was less than the rated power of the motor. However, with the change of process conditions, there was a problem of “small horse-drawn cartsâ€. Causes the frequency converter to not operate normally. For example, the No. 1 water joint, the No. 3 upgrade and the KDl 8 station water injection. Low Voltage Drives - Causes of Failure
Due to the incorrect use method or unreasonable setting environment, it will easily cause the inverter to malfunction and malfunction or fail to meet the expected operating results. It is especially important to carefully analyze the causes of failures before they occur. After 6 to 10 years of normal use, the inverter will enter the high-frequency phase of the fault, often causing malfunctions such as burn-out of components, failure, frequent operation of protection functions, etc., which will seriously affect its normal operation.
External electromagnetic induction interference can cause malfunction
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