Unitronics Variable Frequency Drives for Motor and Motion Control

The Tecnologic process control range now includes the latest addition to the Unitronics range – Variable Frequency Drives (also known as VFDs or VFD drives) for motor and motion control. In this article we’ll take a look at what VFDs are, and what the Unitronics VFD range has to offer process control manufacturers.

If you’re familiar with the Unitronics range of PLCs for automation and process control, you’ll already know that the company is constantly developing new products aimed at making the process of developing and building new control systems easier and faster. Unitronics are one of the world’s leading innovators in the area of PLCs with integrated HMIs, helping to slash development time and integration costs. The ever-popular Samba, Vision and UniStream range of PLCs feature built-in touch screens which eliminate the need to spend time integrating a process controller with its HMI, and are provided with free development software, which includes extensive libraries of images, graphs, strings and a range of UI elements, to enable fast and easy logic programming and user interface design.

Now, Unitronics have launched their own range of Variable Frequency Drives which have been designed to integrate with any Unitronics PLC, making it much easier and quicker to develop and deploy control systems involving motion and motor control.


What is a Variable Frequency Drive?

A Variable Frequency Drive (which can also be referred to as a variable speed drive, adjustable frequency drive or variator) is a motor controller which can adjust the speed and/or torque of a motor by varying the voltage and frequency of its power supply. It enables the speed of a motor to be varied automatically and remotely.

This ability to automatically control the speed of a motor, enables the motor to be integrated into a wider control system in which the motor can be turned on or off, speeded up or slowed down, in response to events or values elsewhere in the process – for example, stopping a conveyor or pump if a blockage is detected, or adjusting the speed of a mixer at different stages of a recipe.

Motors are used in a wide variety of industrial process control applications, to regulate the motion of, for example:

  • Conveyor belts
  • Draw belts
  • Fans
  • Agitators and mixers
  • Printing machinery
  • Pumps
  • Pick and place systems
  • Filling and labelling machines
  • Open/close mechanisms for valves, sluices, doors etc
  • and many more

As well as enabling a variety of industrial processes, variable frequency drives also offer a number of benefits for motor controlled systems. By only activating the motor when it is actually needed, using a VFD helps to extend the life of the motor as well as saving energy – an increasingly important feature for system owners, especially when multiplied across tens or hundreds of motors in large scale systems.

The Challenge of VFD Integration

While VFDs have been used for some decades as part of many industrial control systems, for the uses outlined above, the job of integrating them into a process control system has involved some challenges, including:

  • Assigning PLC inputs and outputs, and mapping them to the VFD terminals
  • Designing the signals required for the specific VFD unit (e.g. run, enable, alarms etc) and ensuring that the outgoing signal from the PLC is of the right type for the specific drive unit (i.e. analog or digital, Volts or Amps, and in the correct range).
  • Manually hard wiring connections between the drive and the process controller / PLC.

In short, VFD integration requires significant technical expertise and is time consuming.

For systems with several motors (e.g. multiple conveyor belts, or a range of different moving parts) the challenge is multiplied, especially if different types of VFD are used to control different motors.

Where multiple motors of the same type require integration within a system, settings and connections need to be recorded and applied manually to each VFD unit in turn. Replacing a VFD also requires manual reconnection of the new drive.

Unitronics VFD Drives

Unitronics Variable Frequency Drives have been designed to address many of the challenges mentioned above, making integration easier and faster. As well as faster development times, this also means faster deployment/installation times for end customers and faster diagnosis or replacement in the event of breakdown or upgrades.

Here are some of the key features of a Unitronics VFD drives:


UniLogic Support for Unitronics VFDs

Unitronics VFDs are compatible with all Unitronics PLCs, including Samba and Vision models. However, for maximum ease of development we recommend using a UniStream PLC and its native development software, UniLogic, which now includes specialist support for VFD integration.

This means that setting up parameters and I/O mappings between the PLC and VFD can all be carried out from within UniLogic. An easy to use setup wizard walks the developer through the necessary steps for setting up each VFD, and settings for one VFD can be saved and re-used for other VFDs in the same system, drastically reducing design/deployment times for multi-motor systems. It also means that a VFD can be replaced and setup quickly.

This close integration between PLC and VFD gives the developer 2 key benefits:

Direct operation from UniStream – The developer can program the HMI to display status information about the motor and allow user control of individual or sets of motors via the HMI.

Multi-motor control – The PLC can control multiple VFDs at the same time, enabling logical dependencies relating to the process to be programmed – for instance, ensuring that 2 or more motors are synchronised together, or waiting for one motor to stop before another one starts.


Support for a Range of Motors

Unitronics VFDs are available for a wide range of motor characteristics including:

Phase – Single phase or three phase power supply

Power – From 0.4kW to 110kW

Type – Induction motors or permanent magnet motors


Advanced Features

Unitronics VFDs are also equipped with a range of advanced features to enhance performance and safety, as well as making life easier for developers. These features vary by model and include:

  • Built in EMC filters
  • Built in dynamic braking units
  • Safe Torque Off feature
  • Sensorless vector speed and torque control
  • Modbus RTU fieldbus
  • Heavy-duty overload capacity
  • Choice of mounting options: rail, wall or flange
  • UL approved, CE certified and TÜV-SÜD certified.
  • Remote monitoring and debugging facility either online or via ScopeTrace

For more technical information about Unitronics variable frequency drives download the Product Specification document on the T-UK product page.

Or phone, email or Live Chat with one of our technical team about your project requirements.

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