Daniele Torresin

1MW bi-directional DC solid state circuit breaker based on air cooled reverse blocking-IGCT

In this paper, we present the development of an air-cooled 1MW bi-directional DC Solid State Circuit Breaker (SSCB) based on recently developed 91mm, 2.5kV Reverse Blocking-IGCT (RB-IGCT). The power electronic switch (RB-IGCT) has been designed and optimized to have very low conduction losses, less than 1kW at 1kA (on-state voltage drop <; 1V at 1kA, 400K) and high turn-off current capability (> 6.5kA at 1.6kV, 400K) which are the most important concerns of semiconductor based circuit breaker. We also present the simulation and experimental results at the system level i.e. analyzed the influence of the Surge Arrester (SA) on the over-voltage transients during current interruption. We also analyzed the thermal management for the newly developed SSCB using ANSYS Icepak and validated experimentally.

A Method to Extract the Accurate Junction Temperature of an IGCT During Conduction Using Gate–Cathode Voltage

In this paper, we propose a novel method to extract the accurate junction temperature of an integrated gate commutated thyristor (IGCT) during device conduction (on-state mode), by measuring the gate-cathode voltage of the device. We have shown that the gate-cathode voltage is a function of anode current and junction temperature Tvj. Indeed, the gate-cathode voltage of the device can be easily accessed in real-time operation of the device from its gate-unit without the need of any external power supply or thermal sensors. The method has been tested by both the simulations (semiconductor device simulations) and experiments (static and load cycling tests) for two different types of IGCTs. This method will enable us to continuously monitor the Tvj of the device during real-time operation of the power electronic converter, and hence, to predict and evaluate the remaining lifetime of the device.

Experimental Characterization of an Open Loop Pulsating Heat Pipe Cooler

Pulsating heat pipes (PHP) have emerged in the last years as suitable cooling devices for dissipating the high heat loads generated by electronic devices since they allow to extend the applicability of air cooling in area nowadays covered by water cooling. Two-phase cooling technologies based on the two phase pulsating heat pipe principle are promising solutions because, being entirely passive they can comply with long term operation without maintenance. The main advantage of a PHP compared to conventional thermosyphon technologies for electronics cooling is that a PHP is orientation independent. The authors has developed a novel, compact, and low cost PHP based on automotive technology. The present paper presents the experimental results of an air cooled open loop pulsating heat pipe with optimized manifold design to minimize fluid pressure drops in the fluid turns. The effect of several parameters including filling ratio and heat load are presented. Tests have been done with the refrigerant fluid R245fa in vertical and horizontal orientations. The measurements showed a maximum thermal resistance ranging between 40 and 48 K/kW in vertical and horizontal position respectively for a heat load of 2 kW and air temperature of 20 °C.Copyright

Experimental Investigation of Enhanced Two-Phase Evaporator Using Aluminum Foams

A novel two-phase thermosyphon with a metal foam based evaporator is presented as a solution for the cooling of power-electronic semiconductor modules. A horizontal evaporator configuration is investigated: the evaporator consists of an aluminum chamber, with aluminum foam brazed to the base plate in three different configurations. One of the configurations has an open vapor chamber above the foam, another has foam filling the entire evaporator chamber, and the third has bores drilled in the foam parallel to the base plate from inlet to outlet along the direction of the vapor flow. The aluminum foam has a porosity of 95%, and a pore density of 20 PPI (pores per inch). A liquid distribution and a vapor collector chamber are respectively present at the entrance and at the exit of the evaporator. The power modules are attached on the evaporator body that collects the heat generated during the operation of the semiconductor devices. A vapor riser guides the vapor to a finned-tube air-cooled heat exchanger. A liquid downcomer from the condenser constantly feeds the evaporator channels. The system works with gravity-driven circulation only. The described system was designed and tested with an extensive experimental campaign. The evaporators were tested for power losses ranging between 500 and 3000 W, corresponding to applied heat fluxes between 3 and 20 W/cm2. The experimental results will be presented for inlet air at ambient temperature of 20°C with volumetric flow rates between 100 and 680 m3/h. The working fluid was refrigerant R245fa. The fluid filling effect was investigated. For each evaporator the results will be presented in terms of maximum thermal resistance and cooler base temperature. The base temperature distribution between different evaporators will also be presented and discussed being an important design parameter in power electronics cooling. Thermal resistances were measured between 15 and 30 K/kW. The experimental results indicated a promising conclusion favoring the implementation of aluminum foam evaporators for enhancement of heat transfer during pool boiling.Copyright

Characterisation of a Novel Pulsating Heat Pipe Cooler for Power Electronics at Extreme Ambient Temperatures

A compact and low cost pulsating heat pipe cooler (PHP) based on automotive technology is presented. This technology uses numerous aluminium MultiPort Extruded (MPE) tubes with capillary sized channels disposed in parallel to achieve the desired compactness. The sub-channels of the MPEs are connected in a serpentine manner by means of fluid distribution elements integrated in the evaporator and condenser manifolds. This configuration enables the oscillation of liquid slugs and elongated bubbles between the evaporator and the condenser areas.In the present paper the experimental results of an open loop type PHP with refrigerants fluids R134a and R245fa are presented. Tests have been carried out for air temperatures ranging between −60 and 60 °C at a fixed air flow rate of 480 m3/h and heat loads from 3 to 13 W/cm2. The experimental results show the different thermo-physical properties effect of the two tested fluids on the cooler performances: R134a is more adapted to low saturation temperature than R245fa and the contrary has been observed at high saturation temperatures. This is due to the fact that R245fa reaches its viscous limit at low temperatures while at high temperatures R134a reaches its critical temperature.Copyright