Analysis of the frequency converter in the centrifuge - Power Circuit - Circuit Diagram

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1 Introduction

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, from In view of 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.

The ACS550 used in this paper is ABB's latest intelligent inverter, 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. Application of frequency converter in three-legged centrifuge

The three-legged centrifuge is a vertical centrifuge with a simple structure, strong adaptability to materials and the widest application range. There are two major categories of sedimentation type and filtration type. 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 input and output terminals of the control loop, the definition of macro 9902=5 is adopted.

DI1: manual / automatic start / stop (manual): electric start

DI2: forward/reverse (manual): electric steering is reversed

DI3: EXT1/EXT2 selection: Automatic control of power selection

DI4: Run permission: Once the drive is disconnected, it will stop

DI5: forward/reverse (automatic): electric steering is reversed

DI6: Start / Stop (Auto): Power on

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.