P.T.O. Driven Generators

n this application mechanical energy is obtained from the power take off of a tractor by means of a pulley belt system. Pulley-belt system adapts the tractor's speed to the alternator's speed which is 1500rpm.
Alternator supply of 50Hz, 400 Volt(between phases) in star connection.
On the terminal box:
There is one 3-P socket and two 1-phase socket
There is a 3+1 switch
There is a voltmeter which shows P-P voltage( 400 Volt)
There is a frequency-meter
The generator’s frequency depend directly on its speed of rotation. Speed must be kept constant under any kind of load.