Diesel Gen-set Operation Instructions
80
1) If the voltage is balanced but too low, main excitation winding or rotating
diode may have problems. Please execute the steps below to identify the
problem:
Rectifier diode
The diode on main rectifying component can be measured with multimeter.
Disconnect the flexible conductor connected to each diode at terminal, and measure
its forward and reverse resistance. Sound diode shall have very high (infinite) reverse
resistance and very low forward resistance. The damaged diode takes on fullscale
deflection or reading is infinite both in forward and reverse directions when measured
at 10000
Ω
.
When a sound diode is measured with electronic digital meter, one reading will be
low and the other reading will be high.
Replace the damaged diode
The rectifying component is installed on two plates with positive and negative
electrodes. The main rotor is connected to the rectifying component through the two
plates. Each plate is equipped with 3 diodes. The negative plate is equipped with
reverse biased diode, and positive plate with forward biased diode. Note that polarity
of diode installed onto corresponding plate must be correct. Good mechanical and
electrical connection shall be guaranteed for diode installed onto plate. The diode
must be installed securely, but not too tightly. The recommended tightening torque is
4.06-4.74N•m.
Surge suppressor
Surge suppressor is a metal oxide varistor connected to the diode with two rectifying
plates to prevent instantaneous reverse voltage in winding from damaging the diode.
Without polarity, this device shows an actual infinite reading in both forward and
reverse directions when measured with an ordinary ohmmeter. Its damage can be
detected as signs of breakage can be found when it is damaged due to short circuit. It
shall be replaced if damaged.
Main excitation winding
If output voltage in excitation separation test is still too low after adjustment and
replacement of rectifying component, inspect the winding of main rotor, excitation
stator and rotor, one of which must have problems. The resistance of excitation stator
can be measured at terminals F1 and F2 (F+ and F- of SE350). Excitation rotor is
connected to 6-bolt (diode) terminal. The winding of main rotor is connected to two
