Research Projects

1 Introduction Small waterfalls and rivers are very frequent in the hilly states of India. These natural water sources can be utilized for microhydro power generation, where extension of the national grid is not economical due to challenging terrain [1]. Numerous small-scale installations ranging from 500 W to 1 kW can impact the lives of remote communities, even when the high rainfall limits the output of solar installations. Low-speed permanent magnet synchronous generators (PMSGs) can offer a solution for powering essential household appliances. The adoption of low-speed also reduces or eliminates the need for high ratio gear mechanisms which makes it more compact and efficient generating system. Unlike distributed winding arrangement where the coils are spread across the machine, in a concentrated winding design the coils are placed around adjacent slots. Notably, it was seen the slot requirement is significantly reduced when concentered winding structure is used. In the design of concentric winding PMSG, various design considerations play a vital role in determining the performance and the efficiency of the machine. These include: 1. The selection of winding structure- single layer (SL) or double layer (DL). 2. Winding layout selection which impacts back EMFs and harmonic losses. 3. Positioning of magnet- interior or surface mounted. 4. Selection magnet geometry- oval shaped or rectangular shape. 5. Performance of air-gap harmonics govern by the dimensions of slots and position and shape of tooth-tip. The selection of winding structure: The selection of later(DL or SL) determines Self-inductance, mutual inductance, Fault tolerance, THD in Back EMF, Eddy-currents in magnets [2]. Winding layout selection: Multiple winding layouts are possible for a possible pole-slot combination- all layouts have different winding factor [3, 4]. Best winding factor factor selection is not only important for a near sinusoidal phase voltage. Positioning of magnet: Although magnets are the primary and constant source of magnetic excitation but the relative permeability of the magnet is approximately 1. Therefore, the body of a magnet behave similar to an air-gap. Selection of magnet geometry and material composition: The above mentioned effects are also applicable to the shape of the magnet and material composition of the magnet [5]. Performance of air-gap harmonics: The interaction of coil, tooth-tip, and magnet introduces air-gap harmonics [6]. The presence of air-gap harmonics lead to thermal deterioration of the magnet performance, affecting the overall efficiency of the energy conversion system [7]. 3.1 Our Proposal Design, fabrication and testing of 500 W, PMSG for a 3 m overhead waterfall. These PMSGs can be installed in hilly terrains and should be capable of generating 50V-70V supply, which is sufficient to fulfill the requirement of BLDC fan, LED bulb and other chargeable devices at remote homes.

Keywords: PMSG, Concentrated winding, micro-hydro plant, FEM analysis, Waterfall, low-head hydropower plant