Integrated Motor-Drives Seek Wider Market, User Acceptance

Much fanfare marked the marriage of ac induction motors and variable-frequency drives (VFDs) when these integrated packages became readily available in the marketplace over five years ago. A few integrated products were offered even earlier (see Who was first...? sidebar). However, convergence of the two technologies became practical in the mid-1990s and continues today.

By Frank J. Bartos, Contorl Engineering December 1, 2000
  • Motors and motion control

  • AC drives

  • Variable-frequency drives

  • Speed control

Market views
Who was first with IMD technology?

Much fanfare marked the marriage of ac induction motors and variable-frequency drives (VFDs) when these integrated packages became readily available in the marketplace over five years ago. A few integrated products were offered even earlier (see Who was first…? sidebar). However, convergence of the two technologies became practical in the mid-1990s and continues today.

This emerging product category promised several user benefits. Among them are eliminating separate enclosures; eliminating long, costly cable runs between motor and drive prone to reflected voltage spikes; greatly reducing EMC issues; and opening many more motors to the potential of variable-speed control. Total installed system cost is claimed to be lower versus a separate motor and drive including wiring and enclosure—to the tune of 20-40%, say some suppliers.

Today, integrated motor-drive (IMD) technology offers power output up to 10 hp (7.5 kW). Typical speed range is 10:1, with a few manufacturers going to 50:1. A trio of European products is illustrated, followed by two U.S.-made examples (next page).

At the same time, these combination products appear to be somewhat ahead of their time. Earlier predictions of market growth and power range have been scaled back. Actually, units up to 25 hp were promised by this time. Similarly, more sophisticated controls ( CE , Dec. ’97, pp. 36-44) have not fully developed because of lagging application demands and sales volumes. Yet, IMDs may now be poised for wider user acceptance.


Siemens (Congleton, U.K.; Erlangen, Germany) views advantages of motor/drive combinations in terms of lower installed system cost (wiring, installation, and panel space savings), eliminating reflected voltage spikes, and promoting decentralized control architectures. CombiMaster—Siemens’ second-generation product—includes design and maintenance-oriented benefits, as well.

Kevin Vickery, drive product specialist at Siemens Energy & Automation (Batavia, Ill.), mentions that CombiMaster’s “top-hat” drive is also sold separately to suit flexibility needs of OEMs and other users. Called MMI (MicroMaster Integrated), the electronics package detaches easily from the motor, according to Mr. Vickery. “A drive can be replaced quickly, in case of need, and the control parameter set downloaded in minutes,” he says.

A specially designed motor adapter plate allows quick and safe replacement of a drive (or motor). Electric connection is simplified by incorporating a foolproof plug in the adapter plate. Various adapter plates mate with third-party motors.

This also serves the retrofitting of singlespeed motors.

Users’ concerns

Several IMD manufacturers have refined adapter-plate design to simplify motor or drive replacement in response to customer concerns.

Siemens E&A verifies another user concern about combination motors and drives: Reliability. Despite the durability of IMDs shown in many applications, customers are not completely sold on “safely” locating electronics atop a motor. Further reticence comes from the product’s relative newness. “Historically, separate responsibility applied to a motor and drive, now one person has to take responsibility at the user end,” adds Mr. Vickery.

At Baldor Electric Co. (Fort Smith, Ark.), combining a motor and its controls means “ultimate matching” of components. Designers and manufacturers know exactly how the motor and drive will perform as a unit, explains, Baldor product manager Roddy Yates. Matched performance translates to user benefits.

Introduced in 1995, Baldor’s integrated SmartMotor line has shown steady if not rapid growth. Mainstay applications are in pumps, fans, conveyors, and upgrading a variety of special machines that originally used one (or few) single-speed motor with no space to accommodate a separate VFD.

The product line is being improved and tailored to other applications. For example, washdown style units and a close-coupled pump version have been added. In Baldor’s experience, many applications remain stand alone, with no great customer demand for more elaborate controls or networking of multiple motors. SmartMotor is available in power ratings through 7.5 kW.

To ABB Automation (New Berlin, Wis.), the “Integral Motor” product makes up a small part of the total motors and drives market. “We continue to offer the product line for specific ‘plug and play’ applications,” states Matt Grant, business manager-AC Motors in ABB’s Drives & Power Products Group (D&PPG). “To date, the U.S. market for these motor/drives has been modest, but may have potential, as more and more end-users look to the combined product to operate motor loads on a ‘demand-side’ basis,” he adds.

Other suppliers also concur that the IMD product is just a part of their larger overall motor and drive business.

ABB Motors (Västerås, Sweden) developed the Integral Motor product line, which has a 0.75-7.5 kW power range and offers variable-speed operation from 300-6,000 rpm.

Mark Kenyon, ABB D&PPG manager, product marketing, mentions a joint development that would integrate ABB drives with motors from Marathon Electric (Wausau, Wis.). The new package will include DeviceNet and Profibus, among networking options, and is slated for availability in 1Q01, through ABB sales channels.

Rockwell Automation’s AC Drives Business (Mequon, Wis.) agrees that ownership cost of integrated motor-drives is lower, based on system installed cost. “The manufacturer’s ability to ship a pretested motor and drive package also benefits the user,” says Stan Ho, product manager, Allen-Bradley Drives Business.

On type of control, he says “good” open-loop (V/Hz) control satisfies many applications. Mr. Ho also notes the original vision of stand-alone IMDs is changing to include integration with larger systems and, depending on the network structure, ability to distribute intelligence and control in the plant.

Rockwell’s product is available through 3.7 kW and is sold under two brands—Allen-Bradley 1329I and Reliance Electric VSM 500—representing different market channels.

European sophistication

Lenze (Hameln, Germany; Fairfield, N.J.) offers a choice of two control modes for its IMD product, named 8200 motec. V/Hz control or sensorless vector control (for torque at lower speed) is selectable by software. The company is considering closed-loop control, according to Steffen Habermann, manager of application engineering at Lenze’s Lawrenceville, Ga., training center. He echoes the notion that higher “initial cost” of integrated motor-drives is tough to sell, as the user makes the decision to go to a newer solution.

The 8200 motec offers 50:1 speed range, PID controller, and various network modules (CAN bus, Profibus, Interbus, DeviceNet, and RS-485). By mid-year 2001 the power range will be extended to 7.5 kW at 480 V supply.

Sensorless vector control is likewise featured in SEW-Eurodrive’s (Bruchsal, Germany; Lyman, S.C.) newest Movimot motor-drive product, along with RS-485, DeviceNet, Profibus-DP, AS-i, or Interbus networking choices. Speed range is 50:1 (2-100 Hz). Tim Schumann, corporate electronics engineer at the U.S. facility, notes increased demand here for Movimot over a couple of years ago, but European production numbers are still higher.

Upgrading standard SEW motors to Movimot capability is part of the offering. A retrofit kit, designed for simple assembly, contains the controller and a stator unit, but retains the original rotor. “A typical two-hp motor can be interchanged in less than 30 minutes, if the installation is reasonably accessible,” says Mr. Schumann.

TB Wood’s Inc. (Chambersburg, Pa.) attributes slower growth of IMD technology— in part—to resistance to switch to a newer technology. Its Integrated Motor Drive (actually IMD is a registered product name of TB Wood’s) combines a high-end induction motor and a relatively high-end inverter. In a costsensitive market, this can handicap rapid product acceptance, explains Rick Kirkpatrick, director of marketing for Electronic Products.

Available up to 3-kW size, IMD features 20:1 speed range derived from an “enhanced” type of V/Hz control. “This control method has worked well for IMD. Many applications do not require higher-level control,” adds Mr. Kirkpatrick. TB Wood’s fits the drive and a cooling fan into a cylindrical housing axially configured to the motor. Standard mounting footprint is thereby maintained. DeviceNet communication option will be available January 2001.

Danfoss (Graasten, Denmark; Rockford, Ill.) has expanded presence in the integrated motor/drive arena with the July 1999 acquisition of German motor manufacturer Bauer. As a result, Danfoss adds an all “in-house” IMD product that combines its electric drives with Danfoss Bauer (Esslingen, Germany; Somerset, N.J.) gear motors as part of the Eta Solution line. The original motor/drive offering (FCM 300) continues. It teams the same Danfoss electronics with standard induction motors from Invensys Brook Crompton.

For its part, Invensys Brook Crompton (Huddersfield, U.K.) supplies the same combination product under its own colors and Variable Speed W Motor (VSM) name. “W” denotes worldwide availability.

Another Danish company, Grundfos (Bjerringbro, Denmark; Fresno, Calif.) has a solid connection to IMDs. This major name in industrial pump technology and an original equipment manufacturer uses its MLE integrated VFD motors to power a line of “E-pumps.” Grundfos considers MLE motors less costly in a total installation and potentially more trouble free than a stand-alone VFD solution.

A growing number of worldwide companies supply IMDs, see a table of products in the Online Extra article at . (Servo-based IMDs and other closed-loop units will be covered in a 2001 article.)

Operate, communicate

Operator interfaces to set up, program, and run IMDs include handheld keypads, HMI panels, and serial links to a PC or PLC. Plug-in keypads are most common; some units come with a keypad built into motor. Siemens regards the latter as a “potential weak link” in the design, due to harsh environmental conditions the keypad has to face. Other manufacturers think a built-in keypad limits use in tight spaces.

Rockwell Automation’s Allen-Bradley 1329I product offers either a mounted or plug-in keypad, and remote control via analog input (0-10 V dc or 4-20 mA), PanelView HMI device, or DeviceNet communications. The latter methods suit an application with larger parameter sets and add operator convenience if the IMD unit is “buried” within a machine.

Besides an on-board keypad, SEW-Eurodrive’s IMD features a remote control keypad plus an LCD operator interface available for speed control of up to 31 Movimot units.

European manufacturers appear to be in the lead to add IMD features and options—for example, communications. This feature is now here or coming soon to more U.S.-made motor/drive packages. Communication capability extends IMD advantages. It should satisfy some user concerns for controlling these products remotely and applying them in multi-IMD networks. For more, see User’s Corner online.

The typical IMD package uses a standard ac induction motor, but a gear-motor option is available from most suppliers. Several European manufacturers emphasize the benefits of an integral gear motor—not a gear box add-on—almost to the point of making the standard motor an “option.” It’s a matter of design philosophy and concern for energy usage. A gear motor multiplies output torque, allows lower output speeds, and reduces load inertia reflected on the motor.

ChristerÖjdemark, divisional president of Danfoss Bauer GmbH, told Control Engineering, “Use of integral gear motors is more prominent in Europe. It goes hand in hand with concerns for energy usage and efficient transmission of power.”

Size growth?

As mentioned earlier, power ratings of motor/drive packages have been growing slower than first envisioned. At Rockwell Automation, the present top size is 5 hp. This is a crossover point where heating effects become a substantial design problem. “More thermal issues arise at this point and return on design investment tends not be practical,” says Mr. Ho.

No substantial size increase above 10 hp (7.5 kW) is seen in the near future at Baldor Electric, Lenze, and others. Although a readily available size, it represents a “practical limit” for now. Few exceptions exist.

Siemens mentions “potential” growth to 15 kW, possibly within a year. A notable exception available now is the Compact Drive product from VEM Motors GmbH (Wernigerode, Germany). These IMDs range up to 22 kW and include field-oriented and vector control models. Drives for the smaller units come from Danfoss, while Emotron (Helsingborg, Sweden) supplies the larger electronics units.

Of course, larger power ratings will come as engineers meet design and cost challenges. Above a certain point, however, physical size of hardware makes integration of motors and drives lose all meaning.

The more immediate challenge for integrated motor-drive technology is to pare down initial costs and more clearly promote product benefits to potential users. For IMDs to be a real alternative to traditional motor and drive installations in substantial numbers, some manufacturers need to take a stronger proactive stance—no easy task when it means competing with alternative in-house products.

Market views

Three recent reports provide different glimpses into this evolving motor-drive market segment. Compared to Europe, the U.S. market for IMDs is small, but growing.

In its latest Integrated Motor Drive Survey (1Q2000), Motion Tech Trends (MTT, Inglewood, Calif.) places Europe in the growth stage of market development, while North America is still in the early adoption stage—with just $1.6 million in 1999 sales, going to $16.5 million by 2005. MTT’s figures refer only to “ac induction IMDs” in sizes of 1 hp and above. Long-term, the U.S. IMD market is seen likely to grow to 4-5% of the multibillion dollar overall motors and drives market.

Frost & Sullivan’s (London) late-1999 analysis, European Market for Variable-Speed Motors [another term for IMDs], reflects greater technology acceptance, with 1999 market value of $46.4 million, growing to $195 million by 2006. Compound annual growth rate for the period is reported at 22.8%. Top three European market areas are Germany, Italy, and France at 57.9%, 16.7%, and 10% share of 1999 revenues, respectively.

Another 1999 British report, European & North American Markets for Motors with Built-in Drive, by Intex Management Services (Wellingborough, Northants), paints even a brighter picture, projecting the market to top $500 million by 2005. This includes the substantially smaller U.S. market. Find more on these reports in the Online Extra article at

Who was first with IMD technology?

Ingenious designers integrated motors and electronic controls into a single unit in their development labs long before the 1990s. Concept models and prototype products were likewise demonstrated previously. Other topologies, such as stepper motor or servo motor-based systems, even reached limited production. Grundfos (Bjerringbro, Denmark) combined an induction motor and an inverter drive as early as 1991 to power its extensive line of pumps. Others launched specialty products, as well.

However, the German company Franz Morat KG (Eisenbach) was probably the first to produce an induction motor and variablefrequency drive (VFD) combination for industrial use in 1993. Its “Fumo” product line, rated 0.65-3 kW for 230/460 V input, was quite sophisticated and ahead of its time (see photo). Fumo incorporated a parallel processor device (transputer), several communication options, and its VFD had positioning capability using a built-in encoder option.

Fumo was discontinued in 1996 for reasons unrelated to product functionality, according to Morat and its U.S. subsidiary, Morat Inc. (North Reading, Mass.).

The market did not appear ready for Fumo. This electronically oriented product did not fit well into Morat’s heavy industry focus of gear sets, gear motors, linear actuators, and related products. Fumo’s technology remains available for sale.


Go to for more on:

IMD developments

Products table

Users’ corner

Other suppliers


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Franklin Electric



Mannesmann Dematic

Spang Power Electronics

WEG Electric Motors