Following are the salient features of a Hydro Generator (alternator):
It is 3-ph hydro generator (alternator). It is robust in construction. A separate excitation is given to separate alternator pole by DC generator (Exciter) which is mounted on same shaft. It excites the field winding of alternator. To excite the main exciter there is pilot exciter which is of permanent magnet. The excitation voltage DC 110/220/300V Generated voltage is 3.3KV, 6.6Kv, 11KV, 17.5KV and 20 KV. Number of poles of hydro generator (alternator). is more and is various from 6 to 120 and machines are salient pole type. Hydro generator (alternator). is large diameter and small is length. In case of generator (alternator). coupled with impulse turbine are horizontal shaft and its speed is 100-1000 rpm. In case of hydro generator couple with reaction turbine is vertical shaft and its speed is low 20-500 rpm. Hydro-generator is low speed machine compare to the steam turbine driven generator. Cooling System: The machines are air cooled, cooling is necessary to improve the performance of generator. Protection : 1. Protection against run away (high speed) speeds are provided 2. Over voltage under voltage protection, 3. Over load protection 4. Over & under frequency protection, 5. Over temperature protection are main protections provided to generator.