Page 10 - 3-5kV Induction Motor

Sensor configuration – single-ended installation

During a short shutdown of a motor, Iris capacitive couplers (80 pF) are permanently installed in the
motor terminal box (one for each phase) and are connected through their own junction box to the test
TM
equipment (TGA-B™ portable instrument or PDTracII continuous monitoring system). Such a
configuration of sensor installation can only be implemented if the motor being monitored has at least
30 meters of high-voltage shielded cable connecting the machine to the electrical power system or
switchgear, as the cable length will reduce any electrical noise due to external disturbance and
interference.

Example of motor terminal box layout/modification using 6.9 kV Iris EMC couplers

Iris systems with ATEX certifications
The junction boxes, where signals from 80 pF couplers (Iris EMCs, 6.9 kV and 16 kV) are terminated,
as well as the PDTracII continuous monitor are available in ATEX versions. However, single EMCs or
their installations are not covered by certification, under the relevant Standards – IEC or EN 60079:0,
60079:1 and 60079:15. The EMC couplers use the motor terminal box as its protection method.

Class of equipment in Protection mode Applicable EN Applicable EN
Explosive accordance with 94/9/EC
atmosphere allowed in accordance standard (OJ dated standard for rules
2009-01-27)
with EN standards
harmonization
GAS All groups and categories General rules EN 60079-0:2006 IEC 60079-0:2004
GAS CE II 2G Ex d EN 60079-1:2007 IEC 60079-1:2007
GAS CE II 3G Ex n EN 60079-15:2005 IEC 60079-15:2005

Couplers for PD measurements require a connection to the high voltage terminals of the motor; for
that reason they are generally installed inside the terminal box of the motor.

If installed in a "hazardous area", those terminal boxes must be ATEX-classified.
Therefore couplers installed in that way become a part of the certification of the motor, or of the
terminal box on it. The motor or the box which includes the terminal strip could then require a new
certification of conformity with ATEX standards issued by the certification body.

Mot/Atex/info082013 pag. 2