EPE Association: EPE 2015 - LS1c: Electrical Machines(I)

EPE 2015 - LS1c: Electrical Machines(I)
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2015 ECCE Europe - Conference > EPE 2015 - Topic 04: Electrical Machines and Drive Systems > EPE 2015 - LS1c: Electrical Machines(I)

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   A Comparison of Rotor Bar Material of Squirrel-cage Induction Machines for Efficiency Enhancement Purposes
By Yiqi LIU [View]
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Abstract: This paper provides a comprehensive analysis and comparison of different rotor bar material insquirrel-cage induction machine from electrical, physical and economic perspectives in order to explorethe impacts of rotor bar material on machine efficiency with physical and economic considerations.Specifically, aluminum, copper and silver are selected in this work and studied on three machines ofdifferent ratings, where silver is proposed as a hypothetical rotor bar material to open discussion and toexplore potential possibilities. To provide an overall analysis, an analytical model and a finite-elementmodel of an induction machine are used in this work with their focus on machine efficiency and magneticflux distribution, respectively. It shows that a silver rotor can provide the highest efficiency under alltested loads and machines with efficiency enhancement of 0.20 to 1.55 percentage points compared to thealuminum counterpart depending on the machine rating and load. Moreover, better performance, such aslarger output power, smaller starting torque, more concentrated magnetic flux distribution, etc., areobserved with the increase of rotor bar conductivity. However, the significantly high price of silver couldimpede its usage in most applications currently and copper rotor bar is believed to have the overallsuperiority among the three kinds of material, although it suffers from casting issues due to its highmelting points. Silver rotor bars or silver alloys may be used in energy-limited areas where highefficiency is needed to compete with certain magnetic material.

   Design and Identification of a Lumped-Parameter Thermal Network for Permanent Magnet Synchronous Motors Based on Heat Transfer Theory and Particle Swarm Optimis
By Oliver WALLSCHEID [View]
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Abstract: A lumped-parameter thermal network (LPTN) for a permanent magnet motor (PMSM) is developed to estimate the most crucial motor temperatures. In this contribution a 60 kW PMSM prototype designed for automotive traction drives is used as the investigation basis. Aiming at real-time motor monitoring well-known analytic equations from the heat transfer theory are used to model the dominant heat paths. Based on a three-dimensional approach in cylindrical coordinates a differential-algebraic state-space model with varying parameters (LPV) is proposed. Due to the chosen level of model abstraction as well as motor material data uncertainties signi_cant estimation errors between the LPTN and experimental test bench measurements result. To improve the estimation accuracy particle swarm optimisation (PSO) is applied for strategic _tting of uncertain model parameters with respect to a maximum likelihood cost function. To avoid converging in suboptimal local minima, which is a typical problem of gradient-based standard optimisation methods, the meta-heuristic PSO is utilised for the resulting multi-variable, non-linear and constrained optimisation problem. For the identi_cation process experimental training data is used which is statistically independent from the (cross-)validation pro_les. As a result the maximum estimation error (worst-case) regarding all considered motor component temperatures can be drastically reduced to 8 °C.

   Determining losses of motors designed for converter operation
By Lassi AARNIOVUORI [View]
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Abstract: There exist no generally accepted methods to determine the losses and efficiency of motors designed for converter operation. There exist two alternative methods that are applicable to all motor technologies - the input-output method and the calorimetric method. In this paper, the both methods are used to determinate the losses of the standard 37 kW squirrel cage induction motor. The results obtained with these methods are further analyzed and the uncertainty of the methods are discussed.

   Harmonic Superposition of Conductor Losses in Switched Reluctance Machines
By Mareike SCHENK [View]
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Abstract: Commonly known analytical prediction methods for winding loss in switched reluctance machines providecomparatively inaccurate results but are very fast. Finite element analyses, however, yield ratherexact results but at high computational cost. This paper introduces harmonic superposition as a thirdapproach that promises sufficiently accurate loss estimations at low computational cost. At that point,the method of superposition, which is also used in all analytical methods, is reinvestigated. Conventionalanalytical approaches use analytical approximations to calculate the harmonic loss components, whichare superposed. The proposed approach determines the harmonic components by finite element analysesduring a one-time preprocessing step. The results of this pre-simulation are examined by calculatingthe resistances of every single conductor. Their dependency on frequency, rotor position and current ispresented. In addition to the improved calculation of the harmonic components, a modified superpositionmethod is presented. This modified superposition method takes leakage flux and saturation effects intoaccount. Both superposition methods are applied at an exemplary operating point and the results arecompared to a transient finite element simulation. Simulation results are presented for an automotiveSRM.

EPE 2015 - LS1c: Electrical Machines(I)
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2015 ECCE Europe - Conference > EPE 2015 - Topic 04: Electrical Machines and Drive Systems > EPE 2015 - LS1c: Electrical Machines(I)
	[return to parent folder]

	A Comparison of Rotor Bar Material of Squirrel-cage Induction Machines for Efficiency Enhancement Purposes By Yiqi LIU	[View] [Download]
Abstract: This paper provides a comprehensive analysis and comparison of different rotor bar material insquirrel-cage induction machine from electrical, physical and economic perspectives in order to explorethe impacts of rotor bar material on machine efficiency with physical and economic considerations.Specifically, aluminum, copper and silver are selected in this work and studied on three machines ofdifferent ratings, where silver is proposed as a hypothetical rotor bar material to open discussion and toexplore potential possibilities. To provide an overall analysis, an analytical model and a finite-elementmodel of an induction machine are used in this work with their focus on machine efficiency and magneticflux distribution, respectively. It shows that a silver rotor can provide the highest efficiency under alltested loads and machines with efficiency enhancement of 0.20 to 1.55 percentage points compared to thealuminum counterpart depending on the machine rating and load. Moreover, better performance, such aslarger output power, smaller starting torque, more concentrated magnetic flux distribution, etc., areobserved with the increase of rotor bar conductivity. However, the significantly high price of silver couldimpede its usage in most applications currently and copper rotor bar is believed to have the overallsuperiority among the three kinds of material, although it suffers from casting issues due to its highmelting points. Silver rotor bars or silver alloys may be used in energy-limited areas where highefficiency is needed to compete with certain magnetic material.

	Design and Identification of a Lumped-Parameter Thermal Network for Permanent Magnet Synchronous Motors Based on Heat Transfer Theory and Particle Swarm Optimis By Oliver WALLSCHEID	[View] [Download]
Abstract: A lumped-parameter thermal network (LPTN) for a permanent magnet motor (PMSM) is developed to estimate the most crucial motor temperatures. In this contribution a 60 kW PMSM prototype designed for automotive traction drives is used as the investigation basis. Aiming at real-time motor monitoring well-known analytic equations from the heat transfer theory are used to model the dominant heat paths. Based on a three-dimensional approach in cylindrical coordinates a differential-algebraic state-space model with varying parameters (LPV) is proposed. Due to the chosen level of model abstraction as well as motor material data uncertainties signi_cant estimation errors between the LPTN and experimental test bench measurements result. To improve the estimation accuracy particle swarm optimisation (PSO) is applied for strategic _tting of uncertain model parameters with respect to a maximum likelihood cost function. To avoid converging in suboptimal local minima, which is a typical problem of gradient-based standard optimisation methods, the meta-heuristic PSO is utilised for the resulting multi-variable, non-linear and constrained optimisation problem. For the identi_cation process experimental training data is used which is statistically independent from the (cross-)validation pro_les. As a result the maximum estimation error (worst-case) regarding all considered motor component temperatures can be drastically reduced to 8 °C.

	Determining losses of motors designed for converter operation By Lassi AARNIOVUORI	[View] [Download]
Abstract: There exist no generally accepted methods to determine the losses and efficiency of motors designed for converter operation. There exist two alternative methods that are applicable to all motor technologies - the input-output method and the calorimetric method. In this paper, the both methods are used to determinate the losses of the standard 37 kW squirrel cage induction motor. The results obtained with these methods are further analyzed and the uncertainty of the methods are discussed.

	Harmonic Superposition of Conductor Losses in Switched Reluctance Machines By Mareike SCHENK	[View] [Download]
Abstract: Commonly known analytical prediction methods for winding loss in switched reluctance machines providecomparatively inaccurate results but are very fast. Finite element analyses, however, yield ratherexact results but at high computational cost. This paper introduces harmonic superposition as a thirdapproach that promises sufficiently accurate loss estimations at low computational cost. At that point,the method of superposition, which is also used in all analytical methods, is reinvestigated. Conventionalanalytical approaches use analytical approximations to calculate the harmonic loss components, whichare superposed. The proposed approach determines the harmonic components by finite element analysesduring a one-time preprocessing step. The results of this pre-simulation are examined by calculatingthe resistances of every single conductor. Their dependency on frequency, rotor position and current ispresented. In addition to the improved calculation of the harmonic components, a modified superpositionmethod is presented. This modified superposition method takes leakage flux and saturation effects intoaccount. Both superposition methods are applied at an exemplary operating point and the results arecompared to a transient finite element simulation. Simulation results are presented for an automotiveSRM.