ANALYS AV HALVLEDARBRYTARE : SIMULERING, MÄTNING OCHBERÄKNING AVVÄRMEUTVECKLING OCH TRANSIENTER

Sammanfattning: BAE Systems Hägglunds are using contactors to control the power supply in their vehicle,but a replacer has been developed because the contactors take up a lot of space. The replacer is a self-designed semiconductor switch, which is called Ultra High Power DigitalOutPut or UHPDOP. The UHPDOP is a mosfet controlled switch with three separated channels that is constructed to handle 70A each at 28VDC. There was no accomplished test on the circuit and Hägglunds wanted data on the circuits thermal characteristics and switch characteristics. The purpose of this thesis is to investigate if the UHPDOP is a reasonable replacement forthe contactors that are used today. The aim of this thesis is to collect measurement data of the UHPDOP-circuit to discover possible improvements. Be able to argument for or against the UHPDOP-circuit and be able to take a stand against the accuracy that i is needed in mathematic equations and simulations, for it to give some valued informationat electronic construction. The overall question in this thesis is, how accurate is approximate simulations and mathematic equations compared to measurements, in question about transients and heat development in components. To answer the question simulation, mathematical equations and measurements on transient and heatdevelopment in the circuit has been done. Simulation program LTspice, datasheet, IRcamera and oscilloscope has been used during the work. The result shows that • Mathematic equations with only power development and thermal resistance does not give information that is usable at electronic construction. • Simulation gives good understanding of the transients shape. • The UHPDOP-circuit can handle the heat development and transients that it can be exposed to. But the circuit has a fault construction, the current limiters activating current is too low. Aside from that fault construction, some minor parts can be improved. Nothing important for the function, but it would improve the performance in handling of both heat and transients.