Making a case for a Non-standard frequency axial-flux permanent-magnet generator in an ultra-low speed direct-drive hydrokinetic turbine system

Akraphon Janon; Krittattee Sangounsak; Warat Sriwannarat; Akraphon Janon; Krittattee Sangounsak; Warat Sriwannarat

doi:10.3934/energy.2020.2.156

AIMS Energy

2020, Volume 8, Issue 2: 156-168. doi: 10.3934/energy.2020.2.156

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Research article

Making a case for a Non-standard frequency axial-flux permanent-magnet generator in an ultra-low speed direct-drive hydrokinetic turbine system

1.
Department of Mechanical Engineering, Faculty of Engineering, Khon Kaen University, Khon Kaen 40002, Thailand
2.
Faculty of Engineering, Nakhon Phanom University, Nakhon Phanom 48000, Thailand
3.
Department of Electrical Engineering, Faculty of Engineering, Khon Kaen University, Khon Kaen 40002, Thailand

Received: 02 October 2019 Accepted: 19 February 2020 Published: 06 March 2020

This research project investigates the impacts of the rotor and generator sizes on rotational speed and voltage output of a direct-drive hydrokinetic turbine system. It searches for a possibility of reducing the generator size while possessing the capability to produce sufficient voltage at an ultra-low RPM. The system has a Darrieus rotor that directly drives an axial-flux permanent-magnet generator, hence the friction loss from the transmission system is eliminated. However, the direct-drive system possesses a very low rotational speed, which adversely affects the generator. In particular, the output voltage is not sufficient for regular applications or the generator diameter needs to be enlarged. Numerical models of the rotor and generator were constructed in MATLAB. The rotor and generator sizes were varied under several design conditions. The models delivered design parameters for the system and their relationships. It was found that designing the generator with 50/60 Hz electrical frequency limits the number of slot/phase and hence the maximum output voltage. The study makes a case for designing a generator with electrical frequency other than the standard frequency, where it would be novel to be able to produce a higher voltage when a location with high water velocity is available, in addition to an improved power production. It would allow the generator to produce higher voltage at a given water velocity and rotational speed or have a smaller diameter at a given output voltage.
- Hydrokinetic turbine,
- direct-drive,
- axial-flux generator,
- low speed generator
Citation: Akraphon Janon, Krittattee Sangounsak, Warat Sriwannarat. Making a case for a Non-standard frequency axial-flux permanent-magnet generator in an ultra-low speed direct-drive hydrokinetic turbine system[J]. AIMS Energy, 2020, 8(2): 156-168. doi: 10.3934/energy.2020.2.156

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Abstract

This research project investigates the impacts of the rotor and generator sizes on rotational speed and voltage output of a direct-drive hydrokinetic turbine system. It searches for a possibility of reducing the generator size while possessing the capability to produce sufficient voltage at an ultra-low RPM. The system has a Darrieus rotor that directly drives an axial-flux permanent-magnet generator, hence the friction loss from the transmission system is eliminated. However, the direct-drive system possesses a very low rotational speed, which adversely affects the generator. In particular, the output voltage is not sufficient for regular applications or the generator diameter needs to be enlarged. Numerical models of the rotor and generator were constructed in MATLAB. The rotor and generator sizes were varied under several design conditions. The models delivered design parameters for the system and their relationships. It was found that designing the generator with 50/60 Hz electrical frequency limits the number of slot/phase and hence the maximum output voltage. The study makes a case for designing a generator with electrical frequency other than the standard frequency, where it would be novel to be able to produce a higher voltage when a location with high water velocity is available, in addition to an improved power production. It would allow the generator to produce higher voltage at a given water velocity and rotational speed or have a smaller diameter at a given output voltage.

References

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