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Adjustable Speed Drives

Adjustable Speed Drives (ASD) are also recognized as Variable Speed Drives (VSD) and Variable Frequency Drives (VFD).

Adjustable Speed Drives are an advanced technology for the twenty-first century. Correctly specified, they offer accurate process control through motor speed changes that provide flexibility, efficiency, and energy savings. They enable industrial plants to achieve improved energy intensity.

Adjustable Speed Drives provide induction motors with electrical conditions that allow a motor shaft speed to be adjusted and reversed under precise control. Correctly specified, adjustable speed drives provide a means of energy efficient operation and a route to energy conservation.

RGLSolutions provides experienced and knowledgeable independent specifications for systems and processes that utilize Adjustable Speed Drives. We have extensive design and application experience in Adjustable Speed Drives in both the US and UK/European markets.

RGLSolutions provides experienced and knowledgeable independent solutions for problems that arise in systems and processes that utilize Adjustable Speed Drives.

RGLSolutions can advise if an Adjustable Speed Drive is appropriate for process needs.

Issues that arise associated with Adjustable Speed Drives applications may include:
1. Choosing the right adjustable speed drive for the application
2. Drive rating (sizing)
3. Load types
4. Electrical environment
5. Mechanical environment
6. Voltage Trips
7. Harmonic Current
8. Cross Coupling
9. Voltage Sags
10. Lightening
11. Load Energy Generation
12. Overheating
13. Motor insulation failure
14. The necessity for inverter duty motors
15. Viability of rewinding failed motors
16. The importance of harmonic currents (IEEE 519 standard)
17. Necessity for and correct application of line reactors
18. The impact of long lead effects
19. Bearing noise
20. Bearing failure
21. Motor frame noise

A sample case history involves HVAC adjustable speed fan drives that were reported failing. The initial proposed solution was replacement by hydraulic drives, a technological step backwards. RGLSolutions approach was a technological step forward. Correctly specified line reactors were recommended and the failures stopped.

A correctly specified adjustable speed drive in a well engineered system is reliable and energy efficient.

Roger G. Lawrence Selected Publications:

Evaluation of ASD Systems for Electric Arc Furnace and Argon Oxygen Decarburization Refiner Baghouse Fans
EPRI, Palo Alto, CA 1997 TR 109254

New Application considerations for AC Drives
Association of Energy Engineers; Atlanta, November 1996

Adjustable Speed Drives in Power Plants
CIBO; Raleigh, 1994

Parallel Operation of Darlington Transistors in a Large 480V, 700HP Induction Motor Drive
IEEE Pulp and Paper Conference, Montreal, June 1991 91CH2973-6