The separation machine is a device for separating a mixture of liquid and solid particles, and is mainly classified into a centrifuge, a separator, a filter press, an oil filter, a filter, and the like. Separation machinery is generally a post-processing device in the process, so it is directly related to the quality of the final product. On the whole, there is a big gap between China's separation machinery technology level and foreign advanced level. Mainly manifested in: separation of machinery varieties, specifications, can not fully meet the domestic production needs, especially the separation of materials with high viscosity, fine precision machinery, high efficiency, large production capacity, high degree of automation of the majority of separation machinery rely on imports; separation The mechanism and application technology are backward, the new product development speed is slow; the manufacturing process is backward, the production efficiency is low, the product reliability and stability are poor, the technical level and automation level are low; the supporting equipment and materials can not meet the needs of the separation machinery product production. Especially the quality and reliability of the products are very unstable.

From the development of the separation machine, the digital AC inverter will replace the original electromagnetic speed regulation, DC speed regulation, hydraulic coupling speed regulation, multi-speed motor, and gradually become the main driving device of the separation machine. This article will introduce the design and application of ABB's new ACS550 inverter in the separation machine.

The ACS550 is ABB's latest intelligent frequency converter, which is used for 0.75KW ~ 355KW low voltage AC drive. It precisely controls speed and torque and matches existing standard squirrel cage asynchronous motors. The ACS550 has three control modes, namely scalar V/F control, sensorless vector control, and torque control, so this inverter can be used not only for the simplest motor operation, but also for complex work situations. Its reliable overload capability design can also meet both normal load and heavy duty work.

The drive motor of the separation machine is generally divided into two types: single motor drive and multi-motor drive. This article will mainly introduce the application of the ACS550 inverter as a typical case of a single motor drive and the typical case of driving as a multi-motor. Application of screw centrifuge.

2 , the application of the frequency converter in the three-legged centrifuge

The three-legged centrifuge is a vertical high-speed centrifuge with simple structure, strong adaptability to materials and the widest application range. There are two major categories of sedimentation type and filtration type. The most widely used is the filter type three-legged centrifuge. It can be used to separate fine particles with a particle size of only a few microns, and can also be used for the deliquoring of articles. By adjusting the duration of each operation step, it can be used to separate various suspensions with different degrees of difficulty in filtration, and the washing time of the filter cake can be adjusted to meet different washing requirements. This type of machine is mainly suitable for small and medium-sized production scales, but due to many of the above advantages, it is widely used in pharmaceutical, chemical, light industry, textile, food, machinery manufacturing and other industrial sectors.

In this application, the inverter drives the drum of the centrifuge, the startup is stable, and the separation factor is adjustable; it completely overcomes the shortcomings of the traditional DC carbon brush centrifuge, such as high noise, high failure rate, short service life and unstable speed. It is a replacement product for gravity sedimentation separation equipment. The AC frequency conversion centrifuge has distinctive features and originality in several important indicators such as shock absorption system and variable frequency motor. The common three-legged centrifuge has a single drive power between 3KW and 55KW, and the ACS550 is fully capable.

Application principle of ACS550 in three-legged centrifuge The principle of ACS550 inverter is mainly divided into three parts in its peripheral line:
(1) DC bus UDC+, UDC- terminates the brake list +, ― terminal, and then according to different choices (such as feedback brake connected to the grid three-phase, energy braking is connected to the braking resistor), Tk is the braking unit The internal relay, when the unit fails, Tk action, defined by the terminal DI4 of the inverter, instantaneously block the U/V/W output.

(2) In the control circuit input and output terminals, the definition of macro 9902=5 is used. DI1: manual/automatic start/stop (manual): electric start DI2: forward/reverse (manual): electric power steering is reversed DI3: EXT1/EXT2 selection: Power selection automatic control DI4: Operation permission: Once the inverter is disconnected, it will stop

DI5: forward/reverse (automatic): electric power steering is reversed DI6: starting/stopping (automatic): electric starting

AI1: External speed reference 1: 0...10 V (manual control, potentiometer, reference voltage 10 VDC)
AI2: External speed reference 2: 0...20 mA (automatic control, reference signal: 0...20 mA)
AI1: External speed reference 1: 0...10 V (manual control, reference voltage 10 VDC)
AI2: External speed reference 2: 0...20 mA (automatic control, reference signal: 0...20 mA)
RO2C/2B: Relay output 2, programmable (default action: run)
RO3C/3B: Relay output 3, programmable (default action: fault)
AO1: DC digital display (frequency or speed indication)

When the centrifuge uses the frequency converter, the braking method should give priority to the regenerative braking that feeds back energy to the grid. The electric energy feedback braking is to feedback the braking energy back to the grid for reuse. From the perspective of energy saving, it is the best. The way, and no heat is generated, it is very suitable for installation in flammable applications (because the energy brake will generate a lot of heat). Where it is not appropriate to use such a regenerative braking device, if there is a grid harmonic requirement (because the harmonic coefficient of the general energy feedback braking unit is not ideal), a braking resistor of sufficient capacity should be installed and heat dissipation measures should be taken; Of course, in non-flammable applications, energy-saving braking is mostly used to save one-time installation costs.

The general energy braking unit has the following basic functions:

( 1 ) Parameter setting action voltage setting: The setting voltage 660V or 710V can be set by the DIP switch (the incoming line is 380V level).
Brake usage rate: The working rate of the brake unit can be set by the dial switch. The default value of the general energy consumption brake unit is 10%, but different braking rates can be set due to different braking requirements of the system. , up to 100%.

( 2 ) The state node module is abnormal: when the DC circuit is short-circuited, overloaded or the IGBT module is damaged, the brake unit alarms and the fault relay Tk operates. Heatsink overheating: Brake unit radiator overheat alarm, fault relay Tk action.

When the brake unit is running normally, Tk is closed, the inverter is in the enabled state to work normally; when the fault occurs, Tk is turned on, and by defining the input terminal DI4 of the inverter, the U/V/W output can be instantly blocked. Play a protective role.

For direct feedback braking, there are already mature products, but the cost is generally several times higher than the energy braking. In the realization of two-way energy transmission between the DC link of the frequency converter and the power supply of the incoming line, one of the most effective methods is to use the active inverter technology: the inverter is reverted to the AC power returning to the grid with the same frequency as the grid. Braking is achieved by using a current-tracking PWM rectifier, which makes it easy to achieve bidirectional flow of power with fast dynamic response. At the same time, such a topology allows us to fully control the reactive and active exchange between the AC side and the DC side. Of course, different products have different control methods, we must also pay attention to power factor, harmonic component, output phase and so on.

3 , ABB inverter application in horizontal screw centrifuge

The horizontal screw discharge sedimentation centrifuge (referred to as the horizontal screw centrifuge) is widely used in petroleum, chemical, metallurgy, medicine, food, light industry and other departments. It can be used for solid dewatering and grading, as well as liquid clarification, and plays an important role in the field of centrifuges.

Since the centrifuge has the advantages of large single processing capacity, convenient operation, continuous automatic operation, low labor intensity, low floor space and low maintenance cost, since the 1950s, the screw centrifuge has been obtained in sludge dewatering. Widely used, gradually replacing other dewatering machinery to become the preferred equipment for sludge dewatering in large urban sewage treatment plants. The suspension enters the high-speed rotating drum through the feeding pipe at the center of the auger. Due to the centrifugal force, the heavier or larger particles are thrown to the inner wall of the rotating drum, and the drum is ejected through the injection hole of the small end of the spiral. The lighter solid particles and liquid phase overflow the drum through the overflow hole of the drum head. The suspension is fed by a screw pump that enables stepless speed regulation.

From the development trend, the horizontal screw drive has developed from the eddy current brake with severe energy consumption to the most mainstream dual-motor double-conversion drive. In a typical decanter centrifuge, there are two transmission shafts: one shaft drives the cylinder to rotate and the other shaft drives the cylinder shaft to rotate, and the rotational speed of the two requires precise cooperation. The variable frequency vector control automatically adapts to the load change for different liquid concentrations, and completes the centrifugal separation process efficiently and reliably. The specific separation control function is integrated into the PLC centrifuge control software. From the wiring mode, the AC power grid is connected to the incoming end of the main inverter. The DC bus of the two inverters is directly connected in parallel with the auxiliary drive. The inverter is not directly connected to the incoming line 380V, so that energy sharing can be realized conveniently and reliably. Under normal operating conditions, the auxiliary machine is in the power generation state, the main motor is in the electric state, the auxiliary machine generates electricity, and the bus voltage is pumped up, and then the bus is connected to the bus, and the pumping voltage is consumed on the main machine, thereby reducing the The energy absorbed by the grid plays a role in energy conservation.

In this scheme, the active current required by the auxiliary motor drive motor and the auxiliary motor occasionally function as the motor (for example, the start-up phase and the acceleration/deceleration transition process) must be provided by the main inverter. Therefore, the main inverter is selected. The power of the line should be taken into account when considering the capacity of the incoming rectifier bridge. The current must be the sum of the electric currents of the two motors. The design of the design is simple in circuit, no need to debug, and the operation reliability is extremely high. The characteristics of the centrifuge control: (1) the vector control mode of the centrifuge speed ensures the correctness of the speed control; (2) the common DC bus can be used; (3) the speed difference control, the encoder is cancelled, and the open loop is used. The sensorless vector control can solve the expensive feedback control scheme with encoder; (4) the load compensation of the barrel drive.

In summary, the frequency conversion application of the decanter centrifuge has the following characteristics:

(1) Energy saving: The common bus double motor double inverter drive is widely used in horizontal screw centrifuges, that is, the main and auxiliary motors are driven by one common inverter, and the DC bus is connected in an appropriate way, which is better solved. This issue is of particular importance today in the face of increasing energy shortages. The speed difference between the spiral and the drum of the modern centrifuge can be automatically adjusted according to the change of the feed. The frequency conversion speed regulation has higher utilization rate of electric energy than the eddy current brake and the hydraulic coupling brake, and the energy consumption is saved. .

(2) Dynamic response fast: The differential speed adjustment process is reduced from a few minutes of the PID regulator to a few seconds of the variable frequency sensorless vector control, and the speed difference adjustment is accurate (even up to ±0.05 rpm), thereby greatly improving the unloading The dry matter content of the material (about 2% in terms of sludge treatment).

(3) Torque control function: The torque control of the ACS550 can be used to easily switch between speed and torque, and to deal with the accumulation of materials in the drum caused by unexpected events, thereby improving work efficiency. The ACS550 centrifuge has a higher effective torque, a minimum continuous torque of 5,000 Nm and an instantaneous load torque of 27,000 Nm.

More mini centrifuge information login:

Sodium Methoxide CAS No.124-41-4

Sodium Methoxide Physicochemical Properties
Density 0.97 g/mL at 20 °C
Boiling point 65 °C
Melting point -98 °C
Molecular formula CH3NaO
Molecular weight 54.024
Flash point 11 °C
Exact quality 54.008160
PSA 23.06000
LogP 0.04670
Appearance traits transparent liquid
Vapor density 1.1 (vs air)
Steam pressure 50 mm Hg ( 20 °C)
Refractive index 1.3700
Storage Conditions
1. Storage: sealed and stored in a cool, dry and dark place
2. Sealed in iron drums, 200kg per barrel, stored in
Cool, ventilated, dry place, fireproof, heatproof, prevent

show. Store and transport according to flammable chemicals.