Designing of a Permanent Magnet and Directly Driven Synchronous Generator for Low Speed Turbines

Micro scale hydro electric power plants are being used in outside national residential areas [1]. Here in such plants, turbine and alternator are coupled to each other by contrivances such as belt pulley and gear mechanism; afterwards the system can produce electricity [2]. Increase at speed difference between turbine and generator which is being run by turbine raises cost and complicacy of system, diminishes feasibility and efficiency. Hence, producers recommend that turbine must be fastened directly [2, 3, 5]. Michell-Banki turbines which are mostly preferred for small rivers drive the generator via belt pulley till 100 kW power, for more than 100 kW power, the generator is driven by turbine via gear box [3]. In this study, a generator which is structured from permanent magnets and driven directly by a Banki turbine has been designed instead of external excited one. It can decrease the setup and operational costs since that the designed permanent magnet generator can eliminate coupling contrivances at contemporary systems. Optimal selection of turbine type for any operational place is determined according to geographical features of venue, water fall and flow and specific speed values of the water. At small water falls (between 2–60 meters long) and big water flows, from 2 kWs up to 200000 kWs, Kaplan type turbines which specific speed is more than 450 rpm is being used [1, 6]. Francis type turbine has a speed range of 45– 550 rpm, they are used at 2–600 meters long medium waterfalls and 2–600000 kWs power plants [1, 6]. Pelton type turbine has a speed range of 2–30 rpm; they are used at 60–1000 meters long big waterfalls and 2– 100000 kWs power plants [6]. Banki type turbines are formed by cogwheel and water spreader mouth. The water comes from spreader mouth penetrates to cogwheel which is shaped as wings, it passes through interior space and it enters into wings from cogwheel’s hoop and so on an occurred secondary force releases the turbine. It is used at up to 200 meters waterfalls and 9 / water flows and in small hydroelectric power plants [6]. In case of Banki type turbine might be used at small water flows, higher efficiency could be obtained. In order to obtain low speed / high torque, permanent magnet motors are used in many industrial applications. That means that a permanent magnet synchronous machine can be used instead of an asynchronous machine system which is connected to a gear box at low speed drives. Because direct drive systems haven’t got gear box costs, maintenance costs are inconsiderable, their efficiencies are high, noise emissions are low, and turning on system is lightweight [9, 13]. Despite the fact that connecting electric motors to the driven machining system without gear box decreases cost and the combined unit’s volume which contains motor, gear box and others, it also redounds system reliability. In researches made recently, electric motors which produce high torques at low speed have been designed [3, 4, 7].


Introduction
Micro scale hydro electric power plants are being used in outside national residential areas [1].Here in such plants, turbine and alternator are coupled to each other by contrivances such as belt pulley and gear mechanism; afterwards the system can produce electricity [2].Increase at speed difference between turbine and generator which is being run by turbine raises cost and complicacy of system, diminishes feasibility and efficiency.Hence, producers recommend that turbine must be fastened directly [2,3,5].Michell-Banki turbines which are mostly preferred for small rivers drive the generator via belt pulley till 100 kW power, for more than 100 kW power, the generator is driven by turbine via gear box [3].
In this study, a generator which is structured from permanent magnets and driven directly by a Banki turbine has been designed instead of external excited one.It can decrease the setup and operational costs since that the designed permanent magnet generator can eliminate coupling contrivances at contemporary systems.
Optimal selection of turbine type for any operational place is determined according to geographical features of venue, water fall and flow and specific speed values of the water.At small water falls (between 2-60 meters long) and big water flows, from 2 kWs up to 200000 kWs, Kaplan type turbines which specific speed is more than 450 rpm is being used [1,6].Francis type turbine has a speed range of 45-550 rpm, they are used at 2-600 meters long medium waterfalls and 2-600000 kWs power plants [1,6].
Pelton type turbine has a speed range of 2-30 rpm; they are used at 60-1000 meters long big waterfalls and 2-100000 kWs power plants [6].Banki type turbines are formed by cogwheel and water spreader mouth.The water comes from spreader mouth penetrates to cogwheel which is shaped as wings, it passes through interior space and it enters into wings from cogwheel's hoop and so on an occurred secondary force releases the turbine.It is used at up to 200 meters waterfalls and 9 / water flows and in small hydroelectric power plants [6].In case of Banki type turbine might be used at small water flows, higher efficiency could be obtained.
In order to obtain low speed / high torque, permanent magnet motors are used in many industrial applications.That means that a permanent magnet synchronous machine can be used instead of an asynchronous machine system which is connected to a gear box at low speed drives.Because direct drive systems haven't got gear box costs, maintenance costs are inconsiderable, their efficiencies are high, noise emissions are low, and turning on system is lightweight [9,13].Despite the fact that connecting electric motors to the driven machining system without gear box decreases cost and the combined unit's volume which contains motor, gear box and others, it also redounds system reliability.In researches made recently, electric motors which produce high torques at low speed have been designed [3,4,7].

The Used Material and Method in Design
The losses in electrical machines are happened as ferrite and core losses at active magnetic parts and as Cu losses at electrical circuits of the machine [10,11].The occurrence of Neodmiyum-Iron-Boron (Nd-Fe-B) magnet quietly gives the added value to improvements of permanent magnet structured synchronous machines [8].SmCo magnets follow the developments of NdFeB magnets [10].The magnets which have naturally high energy extensive such as NdFeB affect machine performances relatively in a big ratio [5].Hence, in this design, NdFeB and SmCo which have well magnetized characteristic and low cost have been chosen.
As design parameters, magnetic flux density is calculated from the Eq. 1 and the electro motor force (emf) at air gap is calculated from the (2):

Designing of a Generator
In this st fall turbine ha ike power, s static analyse designed gene boundary con afterwards, an n a sensible fo The stato be decreased r of stator slots     In this stu has been analy density, its wa emf value are finite element structure and complicate for air gap by con value of mag according to F calculated air peak value ca generator is an

Conclusions
In this stu has been desig computer aid generator has and it has be driven machin certain value regarding to th magnetic para have also been In the an the load given terminals.
Fig. even

Table 1
1. 3D model of 2. View of mag le 1. Analysis r