• ENE-EMD-3
  • 電動馬達推動子系統
  • 安裝高效變速裝置
  • 3.6.3    Variable speed drives

    The adjustment of the motor speed through the use of variable speed drives (VSDs) can lead to significant energy savings associated to better process control, less wear in the mechanical equipment and less acoustical noise. When loads vary, VSDs can reduce electrical energy consumption particularly in centrifugal pumps, compressors and fan applications − typically in the range of -4 − 50 %. Materials processing applications like centrifugal machines, mills and machine tools, as well as materials handling applications such as winders, conveyors and elevators, can also benefit both in terms of energy consumption and overall performance through the use of VSDs.
    The use of VSDs can also lead to other benefits including:
    ●extending the useful operating range of the driven equipment
    ●isolating motors from the line, which can reduce motor stress and inefficiency
    ●accurately synchronising multiple motors
    ●improving the speed and reliability of response to changing operating conditions.
    VSDs are not applicable for all applications, in particular where the load is constant (e.g. fluid bed air input fans, oxidation air compressors, etc.), as the VSD will lose 3 - 4 % of the energy input (rectifying and adjusting the current phase).

    3.6.4    Transmission losses

    Transmission equipment including shafts, belts, chains, and gears should be properly installed and maintained. The transmission system from the motor to the load is a source of losses. These losses can vary significantly, from 0 to 45 %. When possible, use synchronous belts in place of V-belts. Cogged V-belts are more efficient than conventional V-belts. Helical gears are much more efficient than worm gears. Direct coupling has to be the best possible option (where technically feasible), and V-belts avoided.

    3.6.3    變速裝置


    3.6.4    動力傳動損失


  • Harmonics caused by speed controllers, etc. cause losses in motors and transformers ( see Section 3.5.2). An EEM takes more natural resources (copper and steel) for its production.


  • Electric motor drives exist in practically all industrial plants, where electricity is available.
    The applicability of particular measures, and the extent to which they might save money, depend upon the size and specific nature of the installation. An assessment of the needs of the entire installation and of the system within it can determine which measures are both applicable and profitable. This should be done by a qualified drive system service provider or by qualified in-house engineering staff. In particular, this is important for VSDs and EEMs, where there is a risk of using more energy, rather than savings. It is necessary to treat new drive application designs from parts replacement in existing applications. The assessment conclusions will identify the measures which are applicable to a system, and will include an estimate of the savings, the cost of the measure, as well as the payback time.
    For instance, EEMs include more material (copper and steel) than motors of a lower efficiency. As a result, an EEM has a higher efficiency but also a lower slip frequency ( which results in more rpm) and a higher starting current from the power supply than a motor of standard efficiency. The following examples s how cases where using an EEM is not the optimum solution:
    ●when a HVAC system is working under full load conditions, the replacement of an EEM increases the speed of the ventilators ( because of the lower slip) and subsequently increases the torque load. Using an EEM in this case brings about higher energy consumption than by using a motor of standard efficiency. The design should aim not to increase the final rpm
    ●if the application runs less than 1000 − 2000 hours per year (intermittent drives), the EEM may not produce a significant effect on energy savings (see Economics, below)
    ●if the application has to start and stop frequently, the savings may be lost because of the higher starting current of the EEM
    ●if the application runs mainly with a partial load (e.g. pumps) but for long running times, the savings by using EEM are negligible and a VSD will increase the energy savings.

    例如高能效型馬達(EEM)要用比低效型馬達更多的銅鐵材料,結果EEM雖有較高效率,但同時會有較低的轉差頻率(slip freq.)造成馬達轉速加快,以及比標準型馬達需要更大的起動電流。

  • The price of an EEM motor is about 20 % higher than that of a conventional one  Over its lifetime, approximate costs associated with operating a motor are shown in Figure 3.30:

    When buying or repairing a motor, it is really important to consider the energy consumption and to minimise it as follows:
    ●payback period can be as short as 1 year or less with AC drives
    ●high efficiency motors need a longer payback on energy savings.


  • Energy Efficiency (2009) 3.6.3、3.6.4