BTS-Ex, non-contacting thermal switch unit
Function of BTS-Ex
Ins
tal
lat
ion an
d O
pe
rat
ing
M
anual
/
V
er
s
ion
7
/
3626
-019600
ex
en /
P
rot
ec
ti
o
n c
las
s
0:
publ
ic
/
20
20
-07
-15
10
2.1 Switching element
The switching element is a passive component (ordinary electrical equipment). It is
inserted into the outer wheel or into the turbo coupling shell. The result is a thermal
contact between the switching element and the turbo coupling with the operating fluid.
A coil and a thermostatic switch are integrated in the switching element. The switching
point of the thermostatic switch corresponds to the response temperature of the
switching element.
Below the nominal response temperature, the thermostatic switch is closed and
bridges the coil. Above the nominal response temperature, the thermostatic switch
opens and interrupts the circuit. When the temperature decreases, the thermostatic
switch connects again the circuit. The BTS-Ex is again ready for service (it resets
automatically).
2.2 Initiator
The initiator has been designed as intrinsically safe, polarized two-wire sensor. It
works to the inductive sensor principle.
An electric oscillator is integrated in the initiator which produces a high-frequency
oscillation. The oscillator has an oscillating circuit as element determining the
frequency, comprising a coil and a capacitor.
The oscillating circuit coil is located in the sensor head. An electromagnetic alternating
field leaves the sensor head via this coil.
2.3 Evaluator
The evaluator is an electronic unit recording the electric pulses and evaluating the
period between the pulses (appropriate equipment with intrinsically safe circuit to the
explosive atmosphere).
The evaluation starts by switching on the supply voltage.
After starting the evaluation, monitoring of pulses must be interrupted for an
adjustable period of time (start-up bypass time).
A relay with changeover contact will be released if the number of pulses per unit of
time drops below a certain value.
Nominal response
temperature
Chapter 3.1