The GaN transistors offer a significant performance increase in the low voltage pure sine wave motor inverters by increasing the switching frequency so that only the fundamental sinusoidal voltage is applied to the motor. This is useful for high speed applications where low electromagnetic interference are required, for example in a medical hand-held high-speed drill. The LC output filter in the TAPAS board will filter the harmonics at the switching frequency so that the output waveform contains the fundamental sinusoidal voltage. However, the transistor needs a dead time that for the LM5113-EPC2021 combination is in the tens of nanoseconds and the source-to-drain voltage that is 1.6V, larger that the on-state voltage drop given buy the current and on resistance of 1.8mOhm. This will introduce an error in the fundamental voltage that is dependent on the switching frequency, DClink voltage and output current. This error will affect also the motor control at low speed and startup. This error is little understood for the new generation GaN transistor based inverters.
The goal of the project is to investigate the nonlinearity of the inverter and optimize the method to compensate it, taking into account also the output filter.
The inverter will supply a motor and the output voltage will be measured with a PiscoScop 5444B 16 bit resolution oscilloscope in order to account for the error in the mV range included in the tens of volts of switching output voltage. The output voltage spectrum will evaluate the presence of the distortion. Then the nonlinearity of the inverter will be identified and a compensation algorithm will be implemented.Then the output voltage spectrum will be evaluated again.
This idea will get a TAPAS dev kit.