Energy–Efficient Motor Design – One Trend, Different Approaches
What About Motors That Are Already Installed?
The ErP and motor directive applies to new motors, but what about motors that are already installed? Frank Jüngst from Danfoss believes that there is significant business potential out there. “We see very substantial opportunities for retrofits in the chemical industry. Our estimates indicate that a frequency converter is fitted on only about 20% of the drives.”
This is the case because users have been reluctant to invest the time and money to modify the controller, replace cables, etc. Jüngst made the following observation: “Many people are probably not aware that a Danfoss frequency converter with sine filter can be operated in compliance with EMC regulations without a shielded cable.” The situation is much better on new installations. Jüngst estimates that 80% or more of the motors are equipped with frequency converters.
Are Energy Efficient Motors Worth the Investment?
Are a new motor and new frequency converter really worth the investment? Sebastian Schwarz from Siemens says that the answer is definitely yes. “For identical pumps, the up-front cost of state-of-the-art cascade topology is up to ten times higher per frequency converter compared to simple throttle control.
However, that has to be seen in context. About 1% of total lifecycle cost on a pump system is attributable to throttles. In the case of frequency converters, the figure is still only 2%–5%.” In either case, the cost of energy to drive the pumps is the dominant factor. Since the frequency converter alternative is much more energy efficient when operating conditions vary, Schwarz would argue that the investment is always justified.