EPE Association: EPE 2018 - LS3a: Magnetics and Systems

EPE 2018 - LS3a: Magnetics and Systems
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 01: Devices, Packaging and System Integration > EPE 2018 - LS3a: Magnetics and Systems

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   Current imbalance of parallel connected SiC-MOSFET body diodes
By Seitaro ISHIKAWA [View]
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Abstract: This paper studies the current imbalance of body diodes of parallel connected SiC-MOSFETs in a powermodule. The current imbalance is mainly caused by the difference of electrical characteristics of devices,and also the different values of parasitic impedance of circuit. In This paper, the current imbalance ofthe body diode of parallel connecter SiC-MOSFETs focusing on variations of parasitic inductance wasanalyzed by simulation, and confirmed by experiments. As a result, it was confirmed that the currentimbalance can be suppressed by decreasing the parasitic inductance value and bringing this ratio close to1:1.

   Experiences with Coupling Inductances between Commutation Loop and Gate Circuit in Power Modules
By Matthias SPANG [View]
[Download]

Abstract: The fast commutation of the load current in power modules during switching events causes distortions of the gate voltages due to inductive coupling. In this paper, the relevant coupling inductances are extracted from 3D field simulations taking into account magnetic coupling between all sections of the involved current loops inside the module. For different module layouts, the impact of the coupling inductances on measured and simulated dynamic module behavior is examined, including switching speed, dynamic current sharing and short circuit. Several approaches to improve dynamic current sharing between parallel transistors inside a module are presented and evaluated.

   Induction machine flux variation for active thermal control
By Johannes FALCK [View]
[Download]

Abstract: The decoupled control of induction machine flux and torque allows to drive a desired operation point with different ratios of both components. In this paper this degree of freedom is used to control the losses occurring in the semiconductor devices with the target to reduce the thermal cycles. As thermal cycling is one of the main sources of aging and failures, this approach aims at increasing the lifetime of the semiconductor devices.

   Managing high currents in litz-wire-based medium-frequency transformers
By Thomas GRADINGER [View]
[Download]

Abstract: Paralleling litz wires is often necessary in medium-frequency transformers rated for several hundred Ampères, due to unavailability of wire of large cross-section and the difficulties to bend such wire. Without careful winding design, significant losses may be incurred by circular currents induced between parallel-connected wires. These losses add to the AC losses due to skin and proximity effect on the level of individual strands or bundles within a litz wire. To mitigate circular currents between parallel wires, different transposition schemes are experimentally investigated using windings prepared for a 10 kHz, 240 kVA medium-frequency transformer. The effectiveness of continuous transposition is demonstrated for frequencies from 5 to 20 kHz. Continuous transposition is also shown to be a means of reducing the sensitivity of the AC losses to axial misalignment of the windings, enhancing the robustness of the design. An analytical model is set up for comparison and shown to capture the key phenomena observed experimentally. The practical arrangement of wire transposition is discussed.

EPE 2018 - LS3a: Magnetics and Systems
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 01: Devices, Packaging and System Integration > EPE 2018 - LS3a: Magnetics and Systems
	[return to parent folder]

	Current imbalance of parallel connected SiC-MOSFET body diodes By Seitaro ISHIKAWA	[View] [Download]
Abstract: This paper studies the current imbalance of body diodes of parallel connected SiC-MOSFETs in a powermodule. The current imbalance is mainly caused by the difference of electrical characteristics of devices,and also the different values of parasitic impedance of circuit. In This paper, the current imbalance ofthe body diode of parallel connecter SiC-MOSFETs focusing on variations of parasitic inductance wasanalyzed by simulation, and confirmed by experiments. As a result, it was confirmed that the currentimbalance can be suppressed by decreasing the parasitic inductance value and bringing this ratio close to1:1.

	Experiences with Coupling Inductances between Commutation Loop and Gate Circuit in Power Modules By Matthias SPANG	[View] [Download]
Abstract: The fast commutation of the load current in power modules during switching events causes distortions of the gate voltages due to inductive coupling. In this paper, the relevant coupling inductances are extracted from 3D field simulations taking into account magnetic coupling between all sections of the involved current loops inside the module. For different module layouts, the impact of the coupling inductances on measured and simulated dynamic module behavior is examined, including switching speed, dynamic current sharing and short circuit. Several approaches to improve dynamic current sharing between parallel transistors inside a module are presented and evaluated.

	Induction machine flux variation for active thermal control By Johannes FALCK	[View] [Download]
Abstract: The decoupled control of induction machine flux and torque allows to drive a desired operation point with different ratios of both components. In this paper this degree of freedom is used to control the losses occurring in the semiconductor devices with the target to reduce the thermal cycles. As thermal cycling is one of the main sources of aging and failures, this approach aims at increasing the lifetime of the semiconductor devices.

	Managing high currents in litz-wire-based medium-frequency transformers By Thomas GRADINGER	[View] [Download]
Abstract: Paralleling litz wires is often necessary in medium-frequency transformers rated for several hundred Ampères, due to unavailability of wire of large cross-section and the difficulties to bend such wire. Without careful winding design, significant losses may be incurred by circular currents induced between parallel-connected wires. These losses add to the AC losses due to skin and proximity effect on the level of individual strands or bundles within a litz wire. To mitigate circular currents between parallel wires, different transposition schemes are experimentally investigated using windings prepared for a 10 kHz, 240 kVA medium-frequency transformer. The effectiveness of continuous transposition is demonstrated for frequencies from 5 to 20 kHz. Continuous transposition is also shown to be a means of reducing the sensitivity of the AC losses to axial misalignment of the windings, enhancing the robustness of the design. An analytical model is set up for comparison and shown to capture the key phenomena observed experimentally. The practical arrangement of wire transposition is discussed.