Drives & Motion Control

Variable Speed Drives

Fairfields use a variety of low voltage AC and DC Variable Speed Drives (VSD’s) within the control systems we design, manufacture and install. The incorporation of any VSD into a process provides the fundamental element of speed control or torque. This control can be implemented for a number of reasons:

  • To change the speed or torque of a device for process requirements
  • To protect driven equipment and plant availability with torque limiting control
  • Provide a more controlled start-up, for process requirements
  • Energy saving with a lower start-up current consumption
  • Energy saving by reducing process outputs for fan and pump applications
  • Energy saving by regenerating and re-using the energy from high inertia or braking applications
  • Provide process optimisation with better control
  • Integration of Safe Torque Off safety isolation
  • Provide safe limiting speeds control in safety applications
  • Obtain motor and process data feedback
  • De-centralisation of control systems incorporating VSD into motors
  • Networked control

Combined with the integration of instrumentation to monitor the outputs from the process, installing VSD’s can provide a significant and effective return on investment.

In most cases, the incorporation of a VSD into an application will satisfy not only the primary reason for the upgrade, but will also provide additional benefits.

We have worked with our clients to introduce a control system upgrade plan which utilises the latest VSD features to increase operational efficiency, reduce energy and running costs and, at the same time, meet current safety legislation by utilising the latest drives with integrated safety functions.

As an independent solutions provider, we can evaluate the functional requirements of a particular process and provide either cost effective or innovative solutions from all the current VSD manufacturers, including:

We have incorporated VSD control into a number of applications, including:

  • Leisure rides, including single car rides and multi-car log flumes
  • DC drives on paper de-coiling, slitting and recoiling machines
  • Multiple large VSD’s in a torque sharing arrangement for rotary drum applications
  • Automated cranes
  • Large moving structures including bridges and stadium roofs
  • Complex positioning / pick and place servo applications
  • Steel and aluminium production – transfer, cutting and storage applications
  • Automated positioning and track/trace applications
  • Materials handling
  • Food production machines
  • Pharmaceutical machines

Motor Control

We use four primary types of motor control including; V/f, V/f with encoder, open-loop vector and closed-loop vector.

  • V/f control is useful for its “plug-n-play” simplicity and this means the drive needs very little data from the motor and does not require an encoder or tuning.
  • An encoder can be added to a V/f controller for more precise speed regulation, this gives you the ability to run at a higher frequency.
  • Open-loop vector can be used for more dynamic motor control as it independently controls motor speed and torque.
  • Closed-loop vector control also uses a vector algorithm to determine output voltage it works very similar to an open-loop vector but incorporates an encoder.

VSD Integrated Safety

VSD integrated safety functions can reduce the control component hardware (depending on required SIL or PL) as well as provide more powerful safety concepts. Safe Torque Off (STO) can be used to PLd (performance level data) which allows the VSD to remain powered whilst safety functions are active, providing faster process start-up and less VSD degradation with the powering up of drive electronics.

Higher levels of motion safety can be achieved by monitoring drive speed through functions such as safety limiting speed, safe brake control and safe speed monitoring, which in some drives can be achieved without encoder feedback. This facility can provide a safe environment during machine set up or maintenance where operator interaction cannot be designed out during the design phase of the project.

The inclusion of safety communication capabilities can reduce the hardwired element of both standard control and safety functionality.

Energy Saving

Even a relatively small reduction in speed can give significant savings when you consider that a centrifugal fan or pump running at 80% speed consumes only half of the energy compared to one running at full speed. Combined with the integration of instrumentation to monitor the outputs from the process, installing VSD’s can provide a significant and effective return on investment (ROI).

Applications that the require the dissipation of regenerative power by the VSD into heat via braking resistors could quite simply be adapted to incorporate a regeneration power unit without the need to replace the complete VSD, which will return any regenerative power to the power network to be consumed by other equipment.

Servo Motion and Multi Axis Control

Fairfields use servo control equipment in applications where there is a requirement for precise positioning or multi axis closed loop control, which is outside the performance of ‘standard’ VSD’s. This will include the positioning application and PLC software integration.

Related projects