ABB REF542plus - Number of Starts Protection

Multifunction Protection and Switchgear Control unit REF542plus
Manual: Motor Protection with ATEX-Certification
22,1
C40C110
C40C145
=
°−°
°−°
=k
In accordance with standard [DIN1], however, the constant value should be within a
range of 1.0 to 1.2. If the highest possible setting of the setting constant
2,1k =
is chosen, it is possible to calculate the temperature setting in reverse order.
C141C40 C)40C110()2,1(
2
t
°=°+°−°= ϑ
As a result, it is possible to define the temperature for tripping on the REF542plus
C 141maxT °=
With this setting the thermal memory contents can be expanded to 144%. A warning
signal has to be generated, for instance, if the thermal memory contents of 120% is
reached. This way, it is possible to determine the temperature setting for the warning
signal.
C 124C40 C)40C110(
100
120
Twarn °=°+
⎟
⎠
⎞
⎜
⎝
⎛
°−°=
For the commissioning or after an auxiliary power fail with a long time duration it is
necessary to set the initial temperature Tini. In this case, we recommend for selecting
a temperature for the warm operating condition of the motor, for instance, a tempera-
ture at a thermal memory contents of 100%. Accordingly, an initial temperature of
() C110C40C40C110Tini °
=
°
+
°
−
°=
will be assumed.
Since the motor has to be assumed as being rotor-critical without forced cooling, both
of the time constants as well as for the temperature rise in operating condition as also
for the overload or fault condition should be identical. The time constant can be calcu-
lated by applying equation (11.2).
s1112
2,19,7
19,7
ln
s0,8
22
2
=
−
−
= τ
As a result, the two time constants should be set as follows:
s1112Overheat TC Normal TC
=
=
If the motor is no longer running and is not rotating, cooling-off will take place slowly
as there is no more rotation. Generally, the cooling-off process can be assumed with
time constant that is three times the value for normal operation. Therefore the time
constant for cooling-off at standstill is set as follows:
s 3336 s2111 3 TCoff
=
=
5.4 Number of starts protection
In accordance with the recommendations given in the relevant operation guidelines,
the setting of the number of starts from cold condition is
2 Coldstart of Number
=
1VTA100114-Rev. 04 en PTMV, 19.01.05 Motorprotection 34 / 66
Valid from Version V4D02