Bitzer CT-120-2 Traduction De La Notice D'origine page 49

2.2 Single phase failure and cable short-circuit monitoring
Since monitoring the motor winding temperature of a compressor is relevant to safety, this function must also be
protected against faults.
In the event of a single phase failure of the sensor cable in the temperature control circuit, the resistor value is de-
tected as being too high ( Temperature monitoring ), and the compressor protection device locks out immediately .
Devices conforming to EN/UL60730 are additionally protected against cable short-circuits in the sensor cable, i.e.
they are protected against too low resistance. A short-circuit in the temperature control circuit is identified as a fault
which causes the compressor protection device to lock out immediately .
Devices with cable short-circuit monitoring can therefore not be used in simple circuits for evaluating switch signals,
such as the signals of oil flow switches (Oil flow monitoring with SE-B*).
2.3 Monitoring of rotation direction / phase sequence and phase failure
Phase monitoring consists of checking for a few seconds after compressor start whether all phases are activated in
the correct order and according to the specified voltage. This ensures the correct rotation direction and complete-
ness of the magnetic rotating field at the motor connection. If a wrong rotation direction is detected, the protection
device locks out immediately .
In the compressor's state of delivery, this protection function is fully wired and connected to the compressor protec-
tion device.
Depending on the protection device used, lock-out does not take place immediately in the event of phase asym-
metry or phase failure but only if the fault occurs repeatedly; see also device description.
Phase monitoring is delayed by a few seconds on compressor protection devices that are suitable for soft starters
and frequency inverters. The time it takes for the voltage at the motor terminals to enter the detection range of the
compressor protection device must be significantly shorter than this delay.
2.4 Oil flow and oil pressure monitoring
In the case of more complex compressor protection devices, such as the SE-i1 or the previous models SE-C1 and
SE-C2, an oil pressure switch or oil flow switch can be connected directly to a signal input of the device and evalu-
ated. The protection function takes into account time delays during start and monitoring to avoid unnecessary shut-
offs.
Oil flow monitoring with SE-B*
To enable this function on compressor protection devices without a connection for oil flow monitoring, one or two
SE-B* devices can additionally be used as an evaluation unit, combined with a capacitor (C1) used as a timer (see
figures below). The polarity of the connection cables on the protective device must be determined with a measuring
device.
However, this circuit only works with the SE-B1, -B2 or -B3 compressor protection devices, since these devices do
not detect cable short-circuits. Other devices with cable short-circuit detection would interpret a closed contact in
case of sufficient flow as a short-circuit and this would immediately trigger the lock-out function.
CT-120-2 // PDF Download 49