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Experimental study

The experimental set up (shown in Fig. 1) consists of a 7.5kW, two-pole, and three-phase induction motor coupled to a 4-speed automobile gearbox. Speed of the induction motor is controlled by a Variable-Voltage-Variable-Frequency Drive (VVVFD). The output shaft of the gearbox is connected to a separately excited D.C. motor by a constant-velocity joint. The DC motor acts as a generator. A 5.625kW variable resistor load bank is connected with this DC motor. With this load bank 15 different kinds of loads can be applied ranging from 0 to 5.625kW in the interval of 0.375kW. The load on the gearbox can be changed by varying the resistance load with the help of electrical switches. The four-speed transmission gearbox (shown in Fig. 2) has 2nd, 3rd and 4th gears as synchro meshed gears. The detailed specification of the transmission gearbox is shown in Table 1 .

Fig 1: Experimental setup

Fig 2: a) 2-stage Synchromesh gearbox b) Output gear shaft with 2nd gear (healthy)

Table 1: Specification of the gears

The input speed of gearbox is the mechanical speed of induction motor (f₁).The lay shaft speed (f₂), output shaft frequency (f₃) and tooth meshing frequencies (f_m2, f_m3 and f_m4) can be calculated by using equation 1 & 2.

The line diagram of the gear meshing is shown in Fig 3.

Fig 3: Line diagram of meshing during 2nd gear operation