Product details

How servo drives work

With the emergence of full digital AC servo system, AC servo motor is more and more used in digital control system. In order to adapt to the development trend of digital control, the motion control system mostly uses the full digital AC servo motor as the execution motor. The control mode is realized by pulse train and direction signal

General servo has three control modes: speed control mode, torque control mode, position control mode.

At present, the mainstream servo drivers all use digital signal processor (DSP) as the control core, which can realize more complex control algorithms and realize digitalization, networking and intelligence. Power devices generally use intelligent power module (IPM) as the core design of the drive circuit, IPM internal integrated drive circuit, and has overvoltage, overcurrent, overheating, undervoltage and other fault detection protection circuit, in the main circuit also add a soft start circuit to reduce the impact of the start process on the driver.

The power drive unit first rectifies the input three-phase or mains through the three-phase full-bridge rectifier circuit to obtain the corresponding direct current. The three-phase permanent magnet synchronous AC servo motor is driven by the three-phase sinusoidal PWM voltage inverter after the rectified three-phase power or mains. The whole process of the power drive unit can be simply said to be the AC-DC-AC process. The main topological circuit of the rectifier unit (AC-DC) is the three-phase full-bridge uncontrolled rectifier circuit.

With the large-scale application of servo system, the use of servo drive, servo drive debugging, servo drive maintenance are more important technical issues in today's servo drive, more and more industrial control technology service providers have conducted in-depth research on servo drive technology.

PLC and DCS system in common

①DCS: Distributed control systems (distributedcontrol systems).

PLC: Programmable Logic Controller (PLC). Both have different emphasis and are advanced.

②DCS focuses more on the process control field (such as chemical, smelting, pharmaceutical, etc.) is mainly the monitoring and adjustment control of some field parameters, while PLC focuses on logic control (machining class). Of course, the current PLC can also deal with process control problems well, but there is no DCS professional.

(3) If the simulation quantity is greater than 100 points, DCS is generally used; If the analog quantity is within 100 points, PLC is generally used.

DCS is a "distributed control system", and PLC is just a control "device", the two are the difference between "system" and "device". The system can realize the functions and coordination of any device, and the PLC device only realizes the functions of this unit.

The DCS network is the central nervous system of the whole system, DCS system usually uses the international standard protocol TCP/IP. It is a safe and reliable double redundancy high-speed communication network, the system is more extensible and open. Because the PLC basically works for a single small system, when communicating with other PLC or host computer, the network form used is basically a single network structure, and the network protocol is often inconsistent with international standards.

All I/O modules of DCS system are equipped with CPU, which can realize the acquisition and output signal quality judgment and scalar transformation, fault charging, random replacement. The PLC module is just a simple electrical converter, there is no intelligent chip, and the corresponding unit is all paralyzed after the failure.

What is an I/O unit?

Typically, a process control station consists of several racks, each of which can hold a certain number of modules. The rack where the CPU is located is called the CPU unit. There can only be one CPU unit in the same process station. The other racks that are used only for placing I/O modules are I/O units.

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