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In recent years, the frequency converter has been continuously updated and developed as a kind of industrial control equipment, and it has been widely used in all walks of life. With the continuous maturity of power electronic technology, frequency conversion control theory, and microcomputer control technology, the performance of the inverter has been continuously improved and its functions have been continuously enhanced: such as multi-speed, programmable automatic operation, communication functions, etc., which make the inverter adapt to various application. According to the production process of the crew decanter centrifuge, it can be realized by the multi-speed function control of the frequency converter. In addition, the frequency converter generally has a built-in braking unit or an external braking unit, which can solve the problem of large inertia when the centrifuge is stopped. cause parking difficulties.
There are two drive modes: double-machine variable frequency drive and single-machine variable frequency drive. Using double frequency conversion, the main and auxiliary machines are driven by AC frequency converters respectively. After adding PLC, the drum speed, the speed of the screw propeller, and the speed difference between the screw propeller and the drum can be adjusted at any time. This model can be very good. It is suitable for mud of various properties and different mud treatment requirements.
Single machine variable frequency drive: the main machine is driven by an AC frequency converter, and the auxiliary machine is directly driven by an alternating current. The advantage of this driving method is that the structure is simple and the price of the frequency converter is low.
The horizontal centrifuge machine is a large inertia load. When using the inverter control, it is required to increase the braking unit to meet the requirements, which not only saves the installation space for the user, but also saves the cost. It is known from the operating characteristics of the motor that when the actual speed of the motor is higher than the synchronous speed, the motor runs in the generator state. When the centrifuge starts to stop, the output frequency of the inverter begins to decrease according to the deceleration time. Due to the load inertia of the centrifuge at this time The speed change is small, causing the actual speed of the motor to be higher than the synchronous speed, and the motor is in the state of generator braking, which is known by the main circuit of the inverter. At this time, the energy fed back by the motor side will be fed back to the DC circuit through the freewheeling diode of the inverter circuit. On the filter capacitors C1 and C2 of the inverter, the bus voltage of the inverter will rise at this time, and the excessively high pumping voltage will cause the inverter to have overvoltage protection and even damage the inverter. When the control circuit of the braking unit detects that the DC bus voltage reaches a certain value, it controls its switch to turn on, and the braking resistor is connected to the circuit to consume the feedback braking energy of the motor on the resistor to maintain a normal bus voltage.
The industrial centrifuge adopts frequency conversion speed regulation, which can be adjusted according to different process requirements, and can easily choose multi-stage speed regulation operation according to the different mud density. When the load or motor is abnormal, the inverter will stop due to fault and quickly block the output, which can protect the motor in time.