Silicon Carbide (SiC)

Transcription

1 Silicon Carbide (SiC) High junction temperature Hans Bängtsson

2 Properties of Silicon Carbide Important properties of SiC in traction applications High junction temperature Low losses, especially switch losses Parallel connection of components High voltage 2

3 SiC components Different kinds of Silicon Carbide components BJT Bipolar Junction Transistor JFET MOSFET 3

4 4 Silicon Carbide Components

5 BJT Bipolar Junction Transistor Low on-state voltage losses Current controlled more complicated base drive unit High voltage capability 5

6 JFET Field effect transistor Normally-on or normally-off Low on-state losses. Normally-on has lower on-state losses than normally-off. The normally-on losses are comparable to the BJT losses Voltage controlled simple gate drive unit Gate drive units of Normally on components must always have supply voltage, otherwise a short circuit Lower voltage capability than BJT Anti-parallell diode can be included in the JFET 6

7 MOSFET Low on-state losses Voltage controlled a simple gate drive unit Lower voltage capability than BJT (Anti-parallell diode is included in the transistor) 7

8 8 High junction temperature

9 Broad band semiconductor Conduction band SiC Requires high temperature for theraml ionisation Valense band Si Conduction band Doping level Requires lower temperature for theraml ionisation Doping level Valense band 9

10 High operating junction temperure Positive Reduced risk of component destruction due to too high junction temperture Share cooling system with other apparatus which has less critical temperature requirement Smaller heatexchanger due to higher temperature difference Negative Higher operating temperature, higher temperture swing Housing does not match the junction temperture capability Silicon Carbide has higher temperature expansion coefficient than Silicon, bi-metal effect with substrate Presspack Press-pack to fully utlize the temperature capability 10

11 Shared cooling system with Combustion Motor Ordinary silicon component with limited temperature capability. The cooling liquid from the combustion motor is too hot to be shared Combustion Motor Heat exchanger Silicon equipped motor inverter Heat exchanger SiC equipped motor inverter Combustion Motor Heat exchanger

12 12 Low losses

13 13 Low on state and switch losses Positive Remeber, Losses in base or gate drive units must be included Negative Low switch losses is a result of fast switching, which increases electro-magnetic interference (EMC)

14 Study of SiC component properties A theoretical study has been performed, in which the SiC properies has been compared with Si components. Following component combination have been studied Si IGBT - Si diode Si IGBT - SiC schottky diode SiC JFET SiC schottky diode 14

15 Test case, simulated dc-supplied system AM MCM AM AM AM The speed and effort of the train together with line voltage The traction system 15

16 Total losses in MCM and motor at 550 Hz switch frequency Semiconductor Losses Si IGBT Si diode 100% Si IGBT SiC diode 75% SIC JFET SiC diode 25% Comment With SiC technology typical power loss reduction is 3-5 times

17 17 Parallel connection of components

18 Improved current raiting Parallel connection of many component is possible due to positive temperature coefficient (PTC). 18

19 19 High voltage

20 Increased voltage capability with SiC IGBT Voltage (V) 20

21 21 SiC at LTH

22 SiC projects at LTH, Lund University Master thesis work. Theoretical modelling of SiC components Master thesis work. A theoretical design of a BAS inverter in a car (Belt driven Alternater and Starter) light hybridasation, 5 kw

23 SiC projects at LTH, Lund University Doctor student Luyu Wang together with Getachew Darge have built a 12 kw three phase inverter, with SiC bipolar junction transistors and with SiC schottky diode. The work includes design of the base drive unit. Customer Bombardier Transportation AB Together with Fairchild TranSiC and QR-tech Luyu Wang has designed and built a silicon carbide based inverter for a hybrid car electical drive system, with 80kW rating is under construction

24 Design aspects of 12 kw 3-phase inverter Three-phase 12 kva VSI at 600 Vdc dclink voltage for motor drive 10 khz switching frequency 3 parallel transistors per position BJT BT1206AC-01, 6 A, 1200V Supplied by Fairchild TranSiC 2 parallel diodes per position Diode IDH15S120, 15 A, 1200V Supplied by Infineon Free convection (no fan)

25 Study of the LTH SiC inverter Measurement to verify important properties Output power On state losses Switch losses Current sharing

26 The LTH 12 kw inverter