Masters thesis - power electronics i Stockholm

What are you going to do:

Bridge legs in DC/AC inverters, for high current low voltage switching, contain switches that normally are
implemented in the form of a number of parallel transistors (MOSFETs) for controlling current supplied to a motor. During the last years, the on-resistance for the MOSFETs has continually been reduced and with them the switching losses in the inverter. But lower switching losses mean faster switching, which usually mean higher levels of electromagnetic emissions.

One factor that affects electromagnetic emissions is the performance of the MOSFET intrinsic body diode. The
performance of this diode has not improved as much as many of the other properties of the MOSFET. The body diode of the MOSFET conducts current in the MOSFETs reverse direction if the transistor is in off state. In certain steps of the switching cycle, the reverse recovery current in the body diode will cause shoot through in the bridge leg, which cause unwanted electromagnetic emissions and extra heating. In the present implementation, there is no way to control the rate of change of the recovery current. In order to avoid fast diode recovery of the transistors and supress the electromagnetic emission a new configuration for a DC/AC bridge leg is proposed. The new configuration strives to lower electromagnetic emissions by lowering the current derivative of the diode recovery.

Master thesis work
A master thesis work is proposed to study/examine and test the new configuration for the DC/AC inverter. The master thesis work main tasks are:

• Simulate basic behavior of new configuration including control pulse generation, LT-Spice.
• Investigate possible inductive element available for the implementation of small size, short duty, high
• peak current inductor.
• Build-up of functional prototype. (Basic parts exist already like power switches and control HW.)
• Implement control for operation of the bridge leg (Basic implementation to start from exists. C-code.)
• Electromagnetic Interference measurements in Inmotions own chamber.
• Master thesis documentation.
• This Master thesis work will be performed at Inmotions location in Stockholm/Tyresö, Solkraftsvägen 13, 135 70
• Stockholm. Financial compensation will provided.

What we offer:

Inmotion AB is a hardware, automotive company that develops and builds electric motors and motor drives in the segments low voltage lift fork trucks and high voltage hybrid motor drives for busses and trucks.

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Extra information

We´re looking forward to receive your application.

Status

Stängd

Education Level

Universitet/Högskolestudier

Location

Stockholm

Working hours per week

40

Type of Contract

Examensarbete

Profession type

Civilingenjör / Arkitekt

Full UK/EU driving license preferred

No

Car Preferred

No

Cover Letter Required

Yes

Languages

Engelska