Why drives are used in PLC

Why drives are used in PLC?

PLCs are revolutionary in the automation industry. The decreasing size of a PLC also consequences are more powerful. PLC can easily work on multiple communication protocols simultaneously. Machine controllers compact PLC-like devices have evolved to take over some of the work which high-end PLCs have been outgrown. The relationship between the drives and the PLCs is going through a time of change.

The manufacturing sector only depends upon machines that convey materials, cool or hot air with fans, pump liquids, pack, and stack finished products. Drivers depend completely on the controlling, co-coordinating power of the PLC.

The PLCs are developed to control the factory machinery. PLC is the specific type of computer. The difference between the PLCs and PC is the programming language. i.e.,ladder logic. It encodes the instructions sequentially.

PLCs communicate with variable speed drives by direct signals or through a digital communications protocol. The drives to operate motors at optimal speed can be realized when they are in real-time, 2-way communication with PLCs. PLCs monitor the drive’s performance, checking the status, the comparison of the target with real output current.

Communication between PLCs and VFDs

PLCs control VFDs using Modbus ASCII and Modbus RTU or Ethernet protocols for real-time control. The communications control all drive functions. Two-way digital communication allows drive commands are controlled by PLC and monitoring the drive parameters. It includes more than 100 commands, parameters, and statuses, and fault codes.

PLC-based control of drives

The PLC architecture, utilized for input/output control applications. Based on banks of relays that are scanned or polled by a central processor. The scanning points decrease the individual points. By this, we got a lower machine response.

PLC-based indexer is designed to accept data in the form of Input/output communication.  Here, the data is in the form of BCD. BCD information selects a distance to move a program to execute, a time delay, etc. The PLCs have poorly performed the operations are math and complicated decision making.

PLCs are select and executes the required motion of sequences when the controller is in stand-alone mode and stored in ROM via the Input/output interface.

The drive needs input from the sensor, a typical link is through a programmable controller. If we want the development, put that PLC into the drive.

PLC has the popularity by the Computation abilities allow more sophisticated control, cost is affordable for controlling systems, it can be applied to control other systems easily and very fast, the reliable components can be used for long years

Relays are used to control the electrical drives, relays allow power to be switched ON and OFF. Relays are made simple logical control devices.

The PLC drives are different from other drives. They are general purpose AC inverters with additional Input and Output and timers and counters. The drives are not using all of their input and outputs in an application.

VFD’s with integrated PLCs

AC drive controlled by either internal or external PLC. AC drives operate as standalone devices to control the speed of AC motors like fans and pumps. AC drives are pair with PLCs then we often speed control be managed. AC drives are intelligent they include, built-in PLCs to work as smart drives.

Working of AC drives

AC drive called a VFD(variable frequency drive), AFD(adjustable frequency drive). We use the VFD. And its main function is to speed up a 3 phase AC induction motor. VFDs have boosted the efficiency of many applications and then gradually accelerate the motor to reduces inrush current during motor startup. So that we can reduce the mechanical stress and electrical stress on the system.

PLC based DC drive

In industry, DC drives are efficient motion control ability. These drives can operate in control mode and local mode. The drive is controlled by the control panel and the overriding control mode is controlled by a Programmable Logic Controller (PLC). The PLC-based drive is for process control in industries. By this, we reduce the wiring complexity. The successful implementation of PLC -drive communication is good for the industry.

Motors and drives for industrial automation applications are,

  • Brushless DC motors
  • Drives
  • Linear switch
  • Integrated motor drives
  • Stepper motors
  • PMDC brush motors
  • Potency gearmotors
  • Housed AC motors
  • Hansen PMDC brush motors
  • Cable solutions


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