What
is the function of rotating rectifier of diesel generator set?
Rotating rectifier is a
device which rotates coaxially with AC exciter. Its main function is to convert
the three-phase AC excitation current output by the armature of the AC exciter
into the DC current through the diode on the rectifier, supply the rotor
winding as the power supply for the excitation current. It is because of the
application of rotating rectifier that the AC synchronous generator gets rid of
the binding of brush, no longer has the trouble of frequent maintenance and
replacement of parts, and also makes the application of the AC synchronous
generator more extensive.
Some rotating rectifiers
of AC synchronous generators are installed on the outside of the AC exciter and
fixed on the shaft with screws for easy installation and maintenance. Some
rotating rectifiers of generators are installed on the inner side of the rear
end cover and directly fixed on the bolts protruding from the armature core of
the exciter, making the structure more compact. There are two kinds of rotating
rectifier circuits: three-phase half wave and three-phase bridge rectifier. If
the three-phase bridge rectifier circuit is adopted, in order to facilitate
installation, reduce the connection line between the rectifier elements and
improve the reliability of the generator operation, the rectifier diodes are of
two tube types, positive and negative poles are exactly opposite, which is
convenient for wiring.
What
is phenomenon when the rotating rectifier failure?
Rotating rectifier is
usually composed of silicon rectifier elements. If one or several rotating
silicon elements in the circuit are damaged, the damaged silicon element will
lose one-way conductivity (both positive and negative conduction), resulting in
a short circuit of the circuit. Once the rotating silicon element is short circuited,
the generator has no output voltage when the unit is running. If the faults are
not found and removed in time, the armature winding of the AC exciter will be
burnt out and the generator will be forced to stop.
What
causes the rotating rectifier failure?
1.The silicon rectifier
diode of rotating rectifier is damaged due to over-voltage or over-current.
2.When the silicon
rectifier element of the rotating rectifier is installed, the torsional moment
is too large, which leads to the deformation of the tube shell and the damage
of the internal silicon wafer.
3.The load power factor
is too low, which causes the excitation current to exceed the rated current of
silicon rectifying element for a long time and damages it.
How
to deal with the problems?
1.Rotating silicon
elements shall be provided according to the current level specified in the
drawing. If there is no drawing data at hand, the standard silicon element can
be relied on according to the excitation current value of the main generator.
At present, the common specifications of rotating rectifiers produced in China
are 16A, 25A, 40A, 70A and 200A.
2.The voltage level of
the rotating silicon element shall be reasonably selected, and the reverse peak
voltage urn of the rotating silicon element shall be 10-15 times of the
excitation voltage UIN.
3.Tighten the nut of
rotating silicon element with proper torque, and tighten the nut with constant
torque wrench. The torque value of tightening the rotating silicon element nut
shall be in accordance with the provisions shown in the manual which provided
by the supplier.
4.Take over-voltage
protection measures. Overvoltage protection is usually equipped with varistor
or resistance capacitance absorption circuit on DC side of rotating rectifier.
Hope the article is
helpful to you. Starlight Power manufacturer also supplies diesel generator
set, cover Cummins, Volvo, Perkins, Deutz, Yuchai, Shangchai, Ricardo, Weichai,
MTU, Doosan etc. Power range 20kw-3000kw. Welcome to contact us by email
sales@dieselgeneratortech.com, we will work with you.
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