Test On Varistor; Replacement Of The Varistor; Test On The Capacitor; Replacement Of The Capacitor - WEG G Serie Manual De Instalación, Operación Y Mantenimiento

Table 6.3: Table of used diodes
Frame WEG designation
160 DS4
200 - 315 DS6
355 - 450 DS8
For other frames, refer to WEG.
6.6.4

Test on varistor

The varistor is the device installed between the two
bridges connecting the diodes and has the purpose of
protecting diodes against overvoltage.
To test the conditions of operation of the varistor an
ohmmeter can be used.
The resistance of a varistor must be very high (± 20,000
ohms).
In case of damages verified in the varistor or if its
resistance is very low, it must be replaced.
6.6.5

Replacement of the varistor

To replace the varistor, WEG recommends to proceed as
orientation to follow:
1. Replace the damaged varistor by a new identical to the
original, as reported in Table 4.8;
2. To replace the varistor, loosen the screws that secure
the bridges connecting the diodes;
3. When removing the varistor, observe carefully how the
components were mounted so that new varistor is
installed the same way;
4. Before mounting the new varistor, make sure that all
contact surfaces of the components are clean, leveled
and smooth so as to ensure a perfect contact between
them;
5. Attach the new varistor tightening the screws that hold
the connecting bridges just enough to make a good
electrical connection, watch the filling with silicone in the
compartment of the new varistor.
6.6.6

Test on the capacitor

The capacitor is the device installed between the two
bridges connecting the diodes and has the purpose of
protecting diodes against voltage surge.
To test the operating conditions of the capacitor a
multimeter can be used with the function of measuring
capacitance.
The capacitance measurement should be according to the
specification for the component;
In case of damages verified in the capacitor or if
capacitance is above the specified tolerance, it must be
replaced.
10680382 Installation, operation and maintenance manual – Synchronous Alternator – G line - Horizontal
Technical
specification
Diode thread M6
AND
20A/1.200V AND
Diode thread M6
CTD
20A/1.200V CTD
Diode thread M8
AND
45A/1.200V AND
Diode thread M8
CTD
45A/1.200V CTD
Diode thread M8
AND
70A/1.200V AND
Diode thread M8
CTD
70A/1.200V CTD
6.6.7

Replacement of the capacitor

To replace the capacitor, WEG recommends to proceed
as orientation to follow:
1. Replace the damaged capacitor by a new identical to
the original, as reported in Table 4.8;
2. To replace the capacitor, loosen the screws that
secure the bridges connecting the diodes;
3. When removing the capacitor, observe carefully how
the components were mounted so that new capacitor
is installed the same way;
4. Before mounting the new capacitor, make sure that
the connection terminals and screws are clean,
ensuring a perfect contact between them.
5. Fix the capacitor again tightening the terminals that
attach to connecting bridges, just enough to make a
good electrical connection. Observe the filling with
silicone in the compartment of the new capacitor.

6.7 AIR FLOW

The air inlets and outlets of the alternator should be kept
clear, so that heat exchange is efficient. If there is
deficiency in heat exchange, the alternator will overheat
and damage the winding (burning of the alternator).
NOTE
If filters are installed in the air inlet, daily
inspect, clean or replace if necessary.

6.8 COMPLETE INSPECTION

The frequency of inspections should be defined according
to the environment where the alternator is installed. The
more aggressive the environment (dirt, oil, salt spray, dust,
etc.) the smaller should be the time interval between
inspections, as follows:
Clean the dirty windings with a brush;

Use a cloth dampened in a suitable solvent to remove

grease, oil and other impurities from the winding;
Dry with dry air;

Blow compressed air through the ducts in the stator

plate package, the rotor and bearings.
NOTE
Compressed air should always be blown after
cleaning, never before.
Drain condensed water;

Clean inside the terminal boxes;

Measure insulation resistance;

ATTENTION
The absence of complete inspections in the
alternator will cause the accumulation of dirt
inside. The operation under these conditions
may reduce the life, cause unwanted
downtime and additional costs for the recovery
of the equipment.
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