Design Process

Research

In the students junior engineering design class the team researched motor controller designs and finished with a small scale application of a motor controller for a small DC motor. This gave each member a strong background in how motor controllers are designed and how they work. Then, early in the first semester of the teams capstone project each member was assigned a set of application notes pertaining to different parts of a motor controller design. After the members had read and learned the information assigned to them, each member gave a presentation using Power Point on their research to the rest of the team. This gave each member a background in all areas of the project with an expert in each field.

A major design decision made for motor controller was to use MOSFETs over IGBTs. This decision was based on the application parameters. If the application uses a voltage above 1000V then IGBTs are a better choice. If the voltage needed is below 250V, MOSFETs are more advantageous. The region between 250V-1000V should be decided based on the application and its switching speeds. The operational voltage will be no more than 180V, therefore MOSFETs will be more power efficient than that of IGBTs. The reason for this is that MOSFETs have a resistive channel and will lose power through this channel. An IGBT's channel is a PN junction so the power losses are negligible. The switching losses are negligible for MOSFETs but relatively high for IGBTs. In a low voltage application, such as this, the power losses due to the resistive channel are relatively low making the MOSFET a better choice for minimizing power losses, which will result in a more efficient motor controller.

A very significant milestone for the team was the calculation and decisions made on the MOSFET driver and MOSFET matching. This allowed the team to select the correct MOSFET drivers for the MOSFETs they were looking to use. The IXFN230N20T was chosen as the MOSFET for the design with the TC4423 as the MOSFET driver. The TC4423 was chosen because of the parameters necessary for the design. Some of the parameters were peak output current of 3000 mA, dual power, maximum voltage of 18 Volts, and a temperature range of -40 to 125 degrees Celsius. The IXFN230N20T was also for the parameters need for the design. Some of the parameters were peak output current of 230 A, maximum power of 1090 Watts, maximum voltage of 200 Volts, and a temperature range of -55 to 175 degrees Celsius.

Below is a link to the application note used for the MOSFET driver research.

Determining MOSFET Driver Needs for Motor Drive Applications Note