Multifunction Protection and Switchgear Control unit REF542plus
Manual: Motor Protection with ATEX-Certification
4.3.1 Setting parameters
For operation purposes, the parameters need to be set as shown below:
Figure 4: Setting parameters for thermal protection
Where:
Nws Permissible number of starts in warm condition
Ncs Permissible number of starts in cold condition
Reset time (trst) Time to decrement the counter
Tws Warm start temperature threshold
The settings should be, in accordance to today standard, provided for 1 warm start
and 2 cold starts. The temperatures for warm motor condition can be specified at 90%
of the thermal capacity contents of the motor. The thermal capacity content of the mo-
tor, in turn, depends on the setting of the thermal overload protection.
The thermal capacity content is determined by the setting in the thermal overload pro-
tection function. For instance, if the settings of this protection function are such that
the environment temperature is selected to be 40°C and the rated motor temperature
is set to 130°C, the entire thermal memory contents is determined by the difference
between these two temperatures. Thus, 90°C corresponds to thermal memory con-
tents of 100%. If the warm condition has been defined to be 90% of the thermal
memory contents, the temperature for the warm start of the motor needs to be set to
(0.9 x 90°C) + 40°C = 121 °C
If according to the “old” Standard the number of start should be set to be 3 cold-start
and 2 warm-start, so the temperature limit for the warm condition should be set ac-
cordingly. In general the temperature limit can be calculated for 50 to 60% of the
thermal memory. After the first start, the motor temperature should then reach the
warm condition of the motor.
1VTA100114-Rev. 04 en PTMV, 19.01.05 Motorprotection 16 / 66
Valid from Version V4D02
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