Variable speed drives reduce maintenance and boost efficiency

Paul Boughton

Variable speed drives (VSDs) have dramatic impacts on plant maintenance - and on plant efficiencies. Sean Ottewell reports.

In the first of several planned extensions, Rockwell Automation has expanded the power range of its Allen-Bradley PowerFlex 755 AC drives to 450 kW/700 hp, providing users with increased application flexibility. Featuring advanced diagnostics and a convenient roll-out design, the PowerFlex 755 AC drive is well-suited for motor control applications in a variety of heavy industries, including oil and gas, tyre and rubber, refining, material handling, metals and mining.

A key feature of the PowerFlex 755 extended power range drive is its roll-out capability, which allows easy access to the drive for fast installation and maintenance. The drive's modular design helps simplify replacement of drive components, such as cooling fans, circuit boards and major subassemblies. This modularity also allows the drive's converter and control pod to remain in the unit while the inverter is rolled out, so control wiring can remain connected. An additional advantage is the ability for the control pod in this drive to be mounted remotely for hassle-free access to low voltage control and diagnostics.

Advanced diagnostic capabilities include indication of blown fuses and blown surge protectors. Not only are these alarms reported to the main control to help ease troubleshooting, but they also provide essential protection inside the drive, helping to protect the customer's investment. Monitoring and tracking of operating data on cooling fans, I/O relay cycles and motor run times also provide valuable data for preventative maintenance, helping to reduce unplanned downtime.

The PowerFlex 755 drive comes equipped with an embedded Ethernet port and five option slots that allow users to tailor the drive to best suit their application. Options include I/O, feedback, safety, additional communications, and auxiliary control power input.

The PowerFlex 755 now supports Rockwell Automation Integrated Motion, allowing it to be configured and controlled using motion profiles and instruction sets in an Allen-Bradley ControlLogix controller with Rockwell Software RSLogix 5000 software. The ability to support variable frequency drives, motion drives, I/O, smart actuators and other EtherNet/IP-connected devices on a common network helps increase design flexibility, improve system performance and reduce engineering costs, says the company.

The Drives & Motion Division of Yaskawa America, has released the A1000 VSD. A full featured drive, the company says that it provides outstanding quality, performance, flexibility, and environmental friendliness through 1000 hp. For new installations or retrofits, the A1000 provides a single robust solution, regardless of a user's application.

Yaskawa says that its focus on developing quality products is well demonstrated in the A1000, having a calculated design life that is twice as long as previous generations (Fig.1). Compatibility with interior and surface permanent magnet motors provides highly efficient, precision control with incredible performance, producing up to 200 per cent torque with or without feedback.

User-friendly configuration tools, including a multi-language LCD display, parameter storage, application presets, and a portable USB copy unit make programming and configuration simple. DriveWizard computer software delivers configuration, monitoring, and trending functions enhanced by direct connectivity through the A1000's standard USB port.

A significant quantity of control points are included as standard. For applications requiring more functionality, the A1000 offers three expansion ports for additional I/O, feedback, and network communications, including DeviceNet, EtherNet/IP, Modbus TCP/IP, Profibus-DP, PROFINET, and MECHATROLINK-II. Embedded applications functions, such as PID control, droop control, and function block programming provide system level control without the use of a stand-alone controller.[Page Break]

A unified solution

Modern manufacturing regimes need higher efficiency, more flexibility and greater reliability - all necessary to reduce manufacturing costs. To meet those needs, Danfoss VLT Drives has developed the VLT FlexConcept.

This new drive system uses modern motor technology combined with the advanced inverter drives and in a unified solution.

The company says it combines the world's most efficient variable frequency drives VLT AutomationDrive FC 302 and VLT Decentral Drive FCD 302 with the highly reliable and hygienic VLT OneGear Drive and compact and efficient permanent magnet (PM) motors. This results in: higher efficiency; fewer variants; lower training and maintenance costs; flexibility; and higher reliability. Overall, says the company, this equates to a reduction in production and manufacturing costs.

Danfoss offers the choice between VLT drives for centralised location in a control room, cabinets or wall-mounted and VLT decentral drives for mounting close or even onto the drive motor. This gives users the maximum flexibility in plant design and maintenance.

Both the geared motor unit VLT OneGearDrive and the VLT Decentral Drive FCD 302 meet the toughest washdown and hygiene-specific conditions - making them the ideal combination for food and beverage plants.

The VLT FlexConcept reduces the number of drive variants in a plant by up to 70 per cent, which also ensures maximum flexibility and the need for the minimum number of spares.

Danfoss says that the high level of energy efficiency (up to 90 per cent withVLT OneGearDrive combined with VLT AutomationDrive FC 302) reduces total cost of ownership by up to 25 per cent compared with conventional systems.[Page Break]

Control is key, too

According to Siemens, while electric motors represent over 65 per cent of the total industrial power demand, approximately 70 per cent of the installed motors today do not use optimal motor control - which is bad news for a greener world.

The good news is that almost every company has the potential to tap into enormous energy savings by using Siemens variable frequency drives (VFDs) for motor control on pumps, fans, and compressors. The energy savings potential is substantial - in some cases up to 70 per cent. But that's just the beginning of the game. Energy-efficient VFD systems can assist in a number of other ways such as reducing production costs, improving product quality, and ultimately lowering carbon dioxide emissions.

Such improvements are boosted by the company's SinaSave software which calculates how great the savings potentials are for a user's specific drive applications: savings of up to 70 per cent. Siemens offers this innovative and user-friendly software to calculate the energy efficiency and it can be downloaded at no charge. SinaSave also functions as an energy savings calculator, showing how quickly an investment in an energy-efficient motor for line supply operation or a frequency converter for variable-speed operation will pay off. Frequently, the payback period is just a few months, says the company.

For line operation, SinaSave's energy savings calculator determines the cost saving and payback period for our energy-saving motors in the high efficiency classes IE2 and NEMA Premium compared with motors of standard efficiency class IE1 or EPACT, individually selected, or common motors - as part of a complete system analysis.

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