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LOT 30 ECO-DESIGN OF ELECTRIC MOTORS Final Meeting Anibal De Almeida ISR – University of Coimbra Brussels, February 10, 2014 1ISR – University of Coimbra.

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Presentation on theme: "LOT 30 ECO-DESIGN OF ELECTRIC MOTORS Final Meeting Anibal De Almeida ISR – University of Coimbra Brussels, February 10, 2014 1ISR – University of Coimbra."— Presentation transcript:

1 LOT 30 ECO-DESIGN OF ELECTRIC MOTORS Final Meeting Anibal De Almeida ISR – University of Coimbra Brussels, February 10, 2014 1ISR – University of Coimbra

2 Task 6 Technical Analysis of BAT Provides general inputs for the identification of improvement potential when compared to the BaseCases. ISR – University of Coimbra2

3 Small induction motors – IR 2 Losses Increasing the cross-section of stator windings - This modification is where the largest gains in efficiency are achieved. High efficiency motors typically contain about 20% more copper than standard efficiency models of equivalent size and rating. Increasing the cross-section of the rotor conductors. Use copper rotor bars – Due to the excellent electrical conductivity of copper (57 MS/m compared to 37 MS/m), replacing the aluminium in a rotor's conductor bars with die-cast copper can produce a significant improvement in the efficiency of an electrical motor. Increase size of the end rings. ISR – University of Coimbra3

4 Small induction motors – IR 2 Losses Reduce rotor bar skew - rotor bars are slightly skewed which helps reduce harmonics Reducing the skew will help reduce the rotor resistance and reactance, thereby providing gains in efficiency. However, care must be taken not increase harmonics. Odd harmonics, particularly the third harmonic, can originate cogging. Reduce the air gap between the stator and rotor - A smaller air gap lowers the magnetizing current the motor draws to maintain the magnetic field across that gap. The motor will then require less current to drive the load and thereby reduce I 2 R losses. For single-phase motors, adding a secondary run capacitor ISR – University of Coimbra4

5 Small induction motors - Magnetic losses Lengthening the lamination stack - reduces the flux density within the stack, therefore reducing core losses. Use of magnetic steel with better magnetic properties hysteresis losses and Eddy currents are reduced because the resistivity of the laminations is higher, reducing the magnitude of the currents. Reduce the laminations thickness - using thinner laminations decreases the cross-sectional area through which the eddy currents are produced, reducing the magnitude of the eddy currents. ISR – University of Coimbra5

6 Small induction motors - Magnetic losses Ensuring adequate insulation between laminations, thus minimizing the flow of current (and I²R losses) through the stack and reducing eddy current losses. Annealing the core steel - After being annealed, the material becomes much easier to magnetize, which means the magnetic domains reorient more easily reducing hysteresis losses. ISR – University of Coimbra6

7 Small induction motors - Mechanical losses Use low friction bearings – These bearings take advantages of better geometry, materials and lubricant to reduce friction by more than 30% when compared to standard bearings Improved cooling – properly designed cooling systems, such as optimized fans, can help reduce ventilation losses. Improved air flow can also help reduce the power required to move the fan. ISR – University of Coimbra7

8 Small synchronous PM Motors ISR – University of Coimbra8

9 Small synchronous PM Motors ISR – University of Coimbra9 Source: Untersuchungen zur Energieeffizienz von Ventilatorsystemen (Analysis about the energyefficiency of ventilator systems) Institute of Air Handling and Refrigeration (ILK), Dresden/Germany, Fachbericht ILK-B-31-13-3839, Dated 24 th June.2013

10 Super-Premium Motors ISR – University of Coimbra10

11 LSPM Hybrid motor with squirrel cage rotor fitted with high energy permanent magnets (NeFeB) making it suitable for direct on line start Interchangeable with induction motors (same output x frame ratio) and similar starting torque ISR – University of Coimbra11

12 LSPM ISR – University of Coimbra12

13 LSPM It is worth noting that the starting kick of LSPMs is quite violent, which can lead to accelerated mechanical wear of the motor and load bearings and/or gears (if any). This can be particularly critical in application with frequent start/stop cycles. ISR – University of Coimbra13

14 Medium Synchronous PM Motors ISR – University of Coimbra14

15 Medium Synchronous PM - Motors ISR – University of Coimbra15 Part-Load Efficiency

16 Switched Reluctance Motors ISR – University of Coimbra16 An SR motor is a doubly salient design with phase coils mounted around diametrically opposite stator poles. Energisation of a phase will cause the rotor to move into alignment with the stator poles, so minimizing the reluctance of the magnetic path. As a high performance variable speed drive, the motor's magnetics are optimized for closed-loop operation. Rotor position feedback is used to control phase energisation in an optimal way to achieve smooth, continuous torque and high efficiency.

17 SR Motor: Rotor ISR – University of Coimbra17 Simple and robust laminated steel construction: no brushes, windings, rotor bars or magnets Minimal losses in rotor – no cage or rotor bars – indefinite stall possible, no limit to frequency of starts – reduced shaft temperatures and prolonged bearing life The simple SR Drive ® rotor has many advantages over conventional types which utilise magnets or conductors

18 SR Motor: Stator ISR – University of Coimbra18 No magnets: straightforward laminated iron construction Simple coil windings: absence of phase overlaps significantly reduces the risk of inter-phase shorts Compact and short coil overhangs make efficient use of active coil area Compact end-windings permit construction of high-performance motors with unusually flat aspect ratios.

19 SR Motor ISR – University of Coimbra19 APPLICATIONS UP TO 75 kW: High speed centrifugal machines, compressors, washing machines, vacuum cleaners, vacuum pumps, HVAC, variable-speed drive systems, machine-tools, automation, traction, etc. T(N.m) n(rpm) ideal a b c Torque Speed Curve

20 Synchronous Reluctance Motors ISR – University of Coimbra20

21 Synchronous Reluctance Motors The rotor design eliminates rotor I 2 R losses. These motors require an electronic controller (VSD) to operate. ISR – University of Coimbra21

22 Synchronous Reluctance Motors ISR – University of Coimbra22 Potential efficiency increase due to rotor loss reduction in SynR Motors

23 Synchronous Reluctance Motors ISR – University of Coimbra23

24 VSD Efficiency ISR – University of Coimbra24 Typical percent of losses for passive front-end converters Factors affecting these losses Switching losses (output stage) 30 to 50 Motor-current and switching- frequency. Line-rectifier20 to 25losses Line-current (nearly proportional to motor power). Forward losses (output stage)15 to 20Motor current. Internal control circuit Losses (microcontroller, internal power supply, display, keyboard, buscommunication, digital and analogue ins/outs…) 5 to 20Nearly constant. Switching losses (line-side converter / active front-end only) -Line-current and switching- frequency (nearly proportional to motor power). Compound losses (line-side converter / active front- end only) -Line-current (nearly proportional to motor power).

25 VSD Efficiency VSD losses are mainly influenced by the switching frequency (the higher the switching frequency, the higher the losses in the drive) and the output current (which is function of output power and load). However low switching frequency can cause torque ripple. Transistors - IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs (Field Effect Transistors) - have nearly completely replaced thyristors in inverter circuits below 1 MW. Overall losses, parts count, and driver cost are markedly reduced with these devices resulting in an increasingly competitive product. ISR – University of Coimbra25

26 VSD Efficiency It must be noted that the energy benefits from using a VSD always come from decreasing the losses of the system on the load side and that if this benefits can be achieved they surpass the losses in the drive itself. ISR – University of Coimbra26

27 Harmonic Generation within VSDs ISR – University of Coimbra27 Typical input current waveform for a 1.5 kW three-phase drive (with supply voltage) and corresponding harmonic spectrum

28 Harmonic Generation within VSDs ISR – University of Coimbra28 Typical input current waveform for a 1.5 kW single-phase drive (with supply voltage) and corresponding harmonic spectrum

29 Harmonic Losses Motors fed from a converter present additional losses, higher than during operation on a sinusoidal system. These additional losses depend on the harmonic spectrum of the impressed supply quantity (either current or voltage) from the converter. Additionally, harmonics may cause significant damage to the motor by producing bearing currents and insulation voltage stress. ISR – University of Coimbra29


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