Test On Varistor; Replacement Of The Varistor; Test On The Capacitor; Replacement Of The Capacitor - WEG AG10 Series Installation, Operation And Maintenance Manual

Table 6.3: Table of diodes
Model WEG designation
AG10 250 AND
AG10 280 DS6
AG10 315 CTD
AND
AG10 355
DS8
AG10 400
CTD
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, proceeds according to the
following guidance:
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 capacitor.
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.
12638144 Installation, operation and maintenance manual – Synchronous Alternator – AG10 line - Horizontal l 41
Technical data
Diode screw M8
45A/1.200V AND
Diode screw M8
45A/1.200V CTD
Diode screw M8
70A/1.200V AND
Diode screw M8
70A/1.200V CTD
6.6.7

Replacement of the capacitor

To replace the capacitor, proceeds according to the
following guidance:
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
unobstructed, 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).
6.8 INSTALLATION AND
MAINTENANCE OF THE
AUXILIARY EXCITER (PMG)
For installation or maintenance of auxiliary exciter (PMG), if
any, consult the specific manual of this equipment.

6.9 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:

Complete disassembly of the alternator;

General cleaning of all components and parts;

Visual inspection of all components and parts

Mechanical and electrical tests;

Ohmic resistance measurement on windings;

Insulation resistance measurement on windings;

Check of connection cables identification;

Bearings replacement;

Complete assembly of the alternator and all its
components and parts.
ATTENTION
After reassembly the alternator, it is advisable to
do electrical tests.
The absence of complete inspections in the
alternator will cause the accumulation of dirt
inside. The operation under these conditions
may reduce the life of the machine and cause
unwanted downtime and additional costs for
the recovery of the equipment.
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