To increase their usability wind and kinetic-tidal generators and Electric Vehicles (EVs) require efficient conversion between mechanical and electrical energy. The brushless dc machine (BLDCM) is entirely suitable for such a task, and to exemplify its use this thesis details a high efficiency kinetic-tidal energy generator test system. To maximise the energy yield it uses a low solidity turbine, an efficient transmission system, a BLDCM generator, and a maximum power point tracker. BLDCM cogging torque is also addressed. Measured results are presented, with the measured efficiency of the water-turbine being 30%in real-world conditions. Although the BLDCM is an efficient energy converter, it requires power electronic control; the soft-switched Actively Clamped Resonant DC Link Inverter (ACRLI) is an ideal choice for such. This thesis details a complete mathematical analysis of the ACRLI topology, and develops formulae for all important voltages, currents, and timing. A complete list of loss formulae for all major components, including a MOSFET clamp device, is presented. These formulae can be used to optimally design ACRLIs, and an optimal design for a 10 kW EV is described. Since the inductor in a high power ACRLI is problematic, this thesis addresses large ferritecored inductor design, analysing hysteresis and eddy current core loss and Litz wire conduction loss. An optimal but non-realisable design is shown, followed by a near-optimal, realisable and economical very low loss inductor design; an inductor was fabricated in accordance with this design and its measured loss in resonant link operation, being less than 20W for the 10kW high current inverter, is consistent with theory. The BLDCM’s applicability in the general EV field has been questioned due to its rectangular torque versus speed characteristic. To modify this characteristic a voltage booster could be used. The ACRLI can provide such boosting with the addition of a few components, the main one being a rectifier grade thyristor, thus creating the Actively Clamped Resonant DC Link-Boost Inverter (ACRL-BI) topology. This new topology is analysed along with an optimal thyristor dv=dt snubber, a suitable current control method with minimum switching frequency, and a novel driver interface for EV use. A 10 kWACRL-BI prototype was built and measured results of resonant and boost operation are shown.

Resonant link inverters for trapezoidal flux electrically commutated machines

In den vorherigen Kapiteln waren verschiedene unipolare Bauelemente wie der JFET, der MOSFET und der SIT beschrieben worden. Wie sich aus den Ableitungen ergeben hat, haben diese Bauelemente 

1.

sehr hohe Schaltgeschwindigkeiten, da bei ihnen keine Ladungsspeicherungseffekte von Minoritatstragern auftreten,




2.

eine geringe Ansteuerleistung, da nur Kapazitaten umgeladen werden mussen,




3.

hohe Durchlaswiderstande, da die niedrig dotierte Driftzone vorhanden sein mus, um hohe Sperr- bzw. Blockierspannungen aufnehmen zu konnen




4.

und sehr viel hohere Kosten bei der Fertigung.

Kombinationen von uni- und bipolaren Leistungsbauelementen

Improved performance of inverters may be obtained by increasing the switching frequency of the power semiconductor devices. Switching frequencies greater than the hard-switched limits may be obtained by using soft-switching techniques, The MOS-controlled thyristor (MCT) is a relatively new device showing a great potential in soft-switching applications involving high-power densities. Hence, the main objective of this paper is to extend the research work done on both soft-switched (resonant) inverters and MCTs by evaluating the operating characteristics of MCTs for switching frequencies up to approximately 75 kHz under a zero-voltage switching condition. A PCB is developed to subject the MCTs and passive components to stresses similar to those actually occurring in the resonant and actively-clamped resonant DC link inverter topologies. In addition, operation results of the operation of the MCT-based active clamp in the actively-clamp resonant DC link inverter and some practical implementation considerations are included. >

M.I. Redivo

Papers

Operating characteristics of MCTs in resonant DC link inverters