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    VFD for hydroextractor

    I. Overview
    The hydroextractor is widely used in the dyeing, washing water and weaving in the textile industry as well as the dehydrating of the washing material in hotels. The modern hydroextractor must satisfy the requirements of different revolving speeds for different materials. Therefore, the revolving speed of the hydroextractor must be able to be regulated, so as to reach the technological requirements. In the past, most hydro extractors adopted the high and low motors. The low-speed acceleration and deceleration motor is used for feeding and discharging in low speed. The high speed revolving is driven by another motor. In deceleration, mechanical brake is used. The transmission system is rather complicated, with a high failure rate. Because the high-speed motor has a rather big capacity, combining the high inertia of the dewatering tank, the starting current is extremely high and the lasting time is rather long.hydroextractor Furthermore, it has a low operating efficiency. And the speed is unable to be regulated.
    In recent years, VFD has been keeping on updating and developing as a kind of industrial controlling device. It has wide application in various industries. As the power electronic technology, frequency control theory, microcomputer control technology are becoming more and more matured, the performance of the VFD has been improved and the functions have also been intensified, such as: multi-stage speed, programmable automatic operation, communication function and so on. So VFD can be used in many situations.
    According to the manufacturing technology of the hydroextractor, the multi-speed functional control of the VFD can be used. The hydroextractor with VFD control system belongs to the approximate constant torque load with big inertia. Therefore, the system requirements can be reached by configuring braking unit and braking resistor on the basis of selecting the AC converter. The built-in braking unit of the 30hp VFD and below power can not only save space, but also save the cost.
    II. Control principle
    High-speed dehydrating, low-speed cloth feeding and discharging.

    • Cloth feeding: Led the wet cloth into the low-speed (1Hz) operating drum through the cropping shelf (controlled by a small motor) evenly.
    • Dehydrating: Start the main motor and speed up to the maximum frequency slowly. The water will be spin-drying under the centrifugal force. Meanwhile, setting time on the timer as the requirements to stop the machine automatically (deceleration + DC braking).
    • Cloth discharging: Led the dry cloth outside through the cropping shelf (controlled by a small motor).

    III. Parameter setting of ATO VFD
    Parameter setting of the 25hp VFD for the hydroextractor

    Function code Name Set value Remark
    P0.03 Operating command channel 1 Terminal operation
    P0.04 Operating direction setting 0 0 Reversal is allowed
    P0.17 Acceleration time 1 240 Set according to the field condition
    P0.18 Deceleration time 1 420
    P0.19 Upper limiting frequency 40
    P0.22 V/F curve setting 4 Muti-stage V/F curve
    P0.23 Frequency value F3 40 Set according to the field condition
    P0.24 Voltage value v3 95
    P0.25 Frequency value F2 25
    P0.26 Voltage value v2 70
    P0.27 Frequency value F1 15
    P0.28 Voltage value v1 30
    P2.05 Halt mode 2 Deceleration + DC braking
    P2.06 DC braking starting frequency in halt 0.8 Set according to the field condition
    P2.07 DC braking time in halt 8
    P2.08 DC braking voltage in halt 10
    P5.02 Overvoltage speed loss selection 1 Allowed
    P5.06 Automatic current limiting 110% Set according to the field condition
    P5.09 Malfunction self-recovery times 10
    P4.01 Function selection of input terminal X2 2 Multi-stage speed 2
    P4.03 Function selection of input terminal X4 17 External fault reset
    P3.14 Acceleration time 2 20 Set according to the field condition
    P3.15 Deceleration time 2 20
    P3.27 Multistage frequency 2 1
    P4.12 Equipment (TA TB TC) output selection 15 Fault of VFD

    IV. Matters needing attention in ATO VFD debugging

    1. The starting of the hydroextractor in inertia load requires a rather big torque. It might cause the condition of big starting current. At this moment, the torque of the VFD can be lifted properly. The current of the VFD increases in the acceleration operation process. When it reaches a certain speed, the liquid will flow out of the hydroextractor under the centrifugal force. In such way, some liquids will be separated in the first. As the revolving speed of the motor further improves, the load will also decrease correspondingly. At this time, the multi-stage V/F curve and automatic current limiting can be set for adjustment as the practical condition on site.
    2. The function of preventing from over-voltage speed loss: In the deceleration process of the VFD, influenced by the load inertia, there might be condition that the practical descending rate of the revolving speed of the motor is lower than the descending rate of the output frequency, the motor will feed electricity to the VFD at this moment, thus increasing the voltage of the DC bus of the VFD. When it reaches the braking voltage, the braking unit takes action. Because the braking unit has a certain usage rate, if the influence of the high inertia continues, the DS bus voltage keeps on increasing. The application of the function of preventing from over-voltage speed loss will compare the over-voltage speed loss point and the practical DC bus voltage automatically in the deceleration process. If the later passes the former, the output power of the VFD will stop declining until it has inspected that the later is lower than the former again, the VFD can conduct decelerated operation.
    3. Acceleration and deceleration time: Influenced by the load inertia, the acceleration and deceleration time of the VFD must be set a proper value. If the time is too short, there might be overflow, overvoltage faults of the VFD. If the time is too long, the operation power of the device might be reduced greatly.

    Buying an ATO VFD for hydroextractor speed control now, 2 hp VFD, 7.5 hp VFD, 15 hp VFD...

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