The operation of a hydro generator may be observed by five characteristics:
In order to be able to determine all the above characteristics, we need to know both the idle running magnetic characteristic Φ=f(θf), and the on-load magnetic characteristic Φ=f(θr).
- Open-circuit characteristic:
U = f(If), with I = 0
Fig. 1. Open-circuit characteristic
- Short-circuit characteristic:
Isc = f(If), with U = 0
Fig. 2. Short-circuit characteristic
- Saturation characteristic:
U = f(If), with I = const. and φ = const.
Idle running characteristic is a particular case of saturation characteristic.
Fig. 3. Idle running characteristic
- Voltage/current characteristic:
U = f(I), with If = const. and φ = const.
Fig. 4. Voltage-current characteristic
- V-curve characteristic:
I = f(If), with P = m·U·I·cosφ = const.
Fig. 5. V-curve characteristic
Using the open-circuit and short-circuit characteristic, we are able to determine the field current and the on-load voltage drop.