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  • IEC 60034-31:2009

  • 9–

2/1554/CD

10.000

Losses [W]

IE2-Motor IE3-Motor IE2-Motor+Converter IE3-Motor+Converter IE2-Motor+Converter+Brake-Coil

1.000

100

1,1

11 Rated Output Power [kW]

110

Figure 2

Typical losses of energy-efficient motors, converters and electro-mechanical brakes

Figure 2 gives an overview of typical losses of energy saving motors, voltage-source frequency converters and brake coils of electro-mechanical motor brakes.

Many industrial plants already have a high energy consumption of the low voltage control circuits (typically 24V power supply). Therefore, high-efficiency low-voltage power supplies should be used. If possible, the factory should be shut down during long standstill periods (weekends, holidays).

In intermittent-duty applications, high-efficiency electrical motors are not very useful and may even use more energy due to their increased inertia and start-up currents. For these applications, the energy consumption during the starting phase can be reduced by ramping with a frequency-converter. Intermediate energy storage may be beneficial when the operating cycle includes frequent regenerative phases (for example hoist drives, lifts, cranes etc.).

5 Efficiency

Motor efficiency is a measure of the effectiveness with which electrical energy is converted to mechanical energy, and is expressed as the ratio of power output to power input:

Efficiency =

OutputPower

InputPower

=

OutputPower

OutputPower + Losses

Motor efficiencies are usually given for rated load, although 3/4 load and 1/2 load may also be provided.

The efficiency of a motor is primarily a function of load, rated power, and speed, as indicated below:

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