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NOTE
The RTD-type thermoresistance allows
monitoring the absolute temperature. With
this information, the relay can perform the
reading of the temperature, as well as the
parameterization for alarm and shutdown
according to the preset temperatures.
The following formula is used to convert into temperature
the value of the ohmic resistance measured by the
thermoresistance type Pt 100.
Formula: - 100 = C
0,386
Where: = ohmic resistance measured on the PT-100
The protective devices, when requested, are listed in the
specific wiring diagram of each alternator. Failure in using
these devices is the user's sole responsibility, and may
result in loss of warranty in case of damage.
4.6.1.1
Temperature limits for the windings
The temperature of the hottest spot of the winding must
be kept below the limit of insulation thermal class. The
total temperature is composed of the ambient
temperature with the temperature rise (T), plus the
difference between the average temperature of the
winding and the hottest spot of the winding. The ambient
temperature is typically at most 40 °C. Above this value,
the working conditions are considered special.
Table 4.4 shows the numerical values and the
composition of the acceptable temperature of the hottest
spot of the winding for insulation classes F and H.
Table 4.4: Insulation class
Insulation class
Ambient temperature
T = temperature rise (resistance method)
Difference between the hottest spot and the
average temperature
Total: temperature of the hottest point
ATTENTION
If the alternator operates with winding
temperatures above the limits of the thermal
class, the life of the insulation and hence of
the alternator is reduced substantially, or it
may even burn.
4.6.1.2
Thermal protections for the bearings
The temperature sensors installed on the bearings are
intended to protect them from damage due to operation
with over temperature.
22
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Installation, operation and maintenance manual
4.6.1.3
The alarm and shutdown temperatures must be set as
low as possible. These temperatures can be determined
based on the results of tests or through the alternator
operating temperature.
The alarm temperature can be set at 10 °C above the
alternator operating temperature at full load considering
the highest ambient temperature of the local. The
temperature values set to shutdown must not exceed the
maximum acceptable temperatures as listed in Table 4.5
and Table 4.6.
4.6.2
The space heater used to prevent condensation of water
during long periods without operation must be
programmed to be always energized after the shutdown
of the alternator and to be de-energized before the
F
H
alternator goes into operation.
°C
40
40
The dimensional drawing and a specific nameplate on the
°C
105 125
alternator indicate the supply voltage and the power of
the installed space heaters.
°C
10
15
°C
155 180
Alarm and shutdown temperatures
Table 4.5: Stator maximum temperature
STATOR WINDING
Maximum temperature settings of
Class
of Insulation
Alarm
F
140
H
155
Table 4.6: Bearing maximum temperature
BEARINGS
Maximum temperature settings of protections (ºC)
Alarm
110
ATTENTION!
The temperature values for alarm and
shutdown can be set based on experience,
but must not exceed the maximum values
indicated in Table 4.5 and Table 4.6.
Space heater
ATTENTION
If the space heaters remain energized while
the machine is in operation, the winding may
be damaged.
protections (ºC)
Shutdown
155
180
Shutdown
120
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