Drive up energy efficiency

The constant-speed approach to AC motors made a lot of sense when energy was cheap and drives technology was in its infancy. With their latest advances, adjustable speed drives can provide one of the best energy efficiency options for a plant.

By Mike Spear, editor at large

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The drives are an “all new” successor to Baldor’s established H range, and, says Crocker, “have been engineered for reliability and ease of use.” The operator keypads are removable and interchangeable, interfacing with all H2 power bases, control and expansion boards. The keypad enclosure is rated NEMA 4X (equivalent to IP66) when mounted on a panel, although it is also designed for remote mounting up to 100 ft. away.

With a choice of open- or closed-loop control, including inverter, encoderless vector, and closed-loop vector operational modes, the H2 series is said by Baldor to offer a solution to all drive application requirements. The company also maintains that the drives are the most reliable industrial units on the market — a claim that is easy to make so early in a product’s lifespan, but one backed up by Baldor’s design strategy that includes failure mode and effect analysis and a manufacturing process that function tests every sub-assembly, as well as stress and full-load testing of the final products. The initial units in the H2 series cover ratings from 1 hp to 60 hp (0.75 kW to 45 kW), with the full range expected to extend to more than 1250 hp (1000 kW) to handle the vast majority of AC-drive applications.

Late last year, Hitachi, Tarrytown, N.Y., announced an optional Ethernet board for its SJ300 and L300P families of AC inverters. The SJ-EN board can be installed into one of the drive’s internal expansion slots, connecting to the user’s network through a standard RJ45 connector. It implements the Modbus/TCP protocol, providing a high-performance, easy-to-use Ethernet interface with no need for special software or hardware, says Charlie Takeuchi, general sales manager of industrial components and equipment.

Priming the pump
As mentioned earlier, one of the most common process applications for AC drives is for pump control. Also at Interkama in April, ABB launched an optional software package for its low-voltage AC industrial drives. Dubbed “Intelligent Pump Control,” the package includes six functions together with ABB’s own Adaptive Programming utility. The company’s Nanette Baur says this enables users to customize drives for specific applications.

Its “Multipump Control” function, initially aimed at water and wastewater utilities, suits any application where several pumps are operated together and the required flow rate is variable. Each pump is controlled by its own drive, with the speed of one being adjusted while the rest run at constant speed. Baur says this results in smooth control with no pressure peaks.

Another of the functions, dubbed “Level Control,” is typically used to control the filling or emptying of wastewater storage tanks. A special feature of the software prevents sediment buildup on the tank walls by randomly varying the surface level within a user-preset range. Fast-ramp starting flushes pipelines clear, and the pump is operated at the optimum point on its efficiency curve to minimize energy consumption. The level-control function can be applied to a single pump, or two to three pumps and drives in parallel.

ABB’s flagship industrial drives form the ACS800 series, which boasts the extraordinarily wide power range of 2/3 hp to 7,000 hp (0.55 kW to 5.6 MW). All feature the company’s Direct Torque Control (DTC) technology, unveiled 10 years ago, but still regarded as something of a benchmark in terms of speed. DTC regulates motor torque and speed directly without the need for separate control of voltage and frequency.

Designed for use in tough environments, the modular range of drives features enclosure protection up to IP54 (which approximates NEMA 4) against dust ingress and splashing water. This generally means they can be used outdoors without the need for additional cabinets. The IP54-protected drive range has recently been extended to 110 kW (135 hp) from the previous maximum of 45 kW (55 hp).
Again in April, Rockwell Automation, Bloomington, Minn., introduced a new line of Allen-Bradley ArmorStart distributed motor controllers that now feature a built-in Powerflex sensorless vector drive. Housed in a robust IP67 (NEMA Type 4) enclosure, the compact drives can be mounted close to the motor (“On-Machine” to use Rockwell’s branding) and come pretested with quick-connect wiring; these features can provide savings on installation time of up to 40%, according to Marketing Manager, Claude Joye. “Manufacturers at all levels are searching for high-performance control devices that will give them greater application flexibility, faster installation and lower engineering costs,” he says.
The ArmorStart drive can be used with motors ranging from 0.5 hp to 5 hp. Factory-installed options include an HOA (hand/off/auto) keypad with jog function, dynamic brake contactor, source brake contactor, EMI filter and shielded motor cable.

Most of today’s drives look quite different from previous generations. Thanks to advances in power electronics, such as insulated-gate bipolar transistors, they can offer the same power as before, but in much smaller packages. However, it is at the user-interface level where the changes are most notable. Whether keypads are detachable or integral with the enclosure, many have the familiar look and feel of today’s cell phone technology — offering up graphical displays and intuitive menus for users to navigate the increasing variety of operational settings.

Supportive software
For those users whose intuition might fail them at a critical time, manufacturers like Yasakawa Electric, New Berlin, Wis., provide software wizards. Downloadable at no charge at www.yasakawa.com, version 6.0 of the company’s DriveWizard now features a greater capacity for remotely viewing, manipulating, troubleshooting and exchanging data with its drives. Parameters can be downloaded to any Yasakawa drive irrespective of its size or rating, making life easier for users working with specific applications on different drives. The DriveWizard can now also store multiple IP addresses for when drives are being networked using Ethernet communication.


Another piece of downloadable software shown at Interkama by Siemens Automation and Drives, Alpharetta, Ga., could be just the thing to put in front of those purchasing managers who think drives are just a commodity item and who simply buy the cheapest option. Sinasave (downloadable at www.siemens.de/energiesparprogramm) can calculate the potential energy savings when using frequency converters for variable-speed systems. For fixed-speed applications, it can show the savings to be accrued from switching to energy-efficient motors. The program takes into account the entire drive train — not just the individual drive.

For constant-speed drives, Sinasave calculates the energy savings and amortization involved in changing to energy-saving motors of a higher class. For variable-speed systems, you input the characteristic plant data and parameters, such as delivery volume and delivery heads in the case of pumps, or mass flow and total pressure difference for fans and blowers, along with data on working shifts, duration of operation and so on. The program then calculates the energy saving effect of using the correct drive system and will provide the payoff period for the investment.
So, now you can prove the benefits of the drive to energy efficiency.

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