Effective isolation transmitter for high-voltage motors
Measuring technology specialist Knick is introducing the ProLine P 44000 series of transmitters with extremely high isolation for use with Pt100 resistance thermometers in high-voltage motors (up to 11 kV).
Insulated temperature monitoring sensors are built into each phase of the winding of high-voltage motors, which are often in use for several decades. Transient overvoltage, voltage spikes as well as thermal and mechanical aging, however, can lead to insulation defects over time, which in turn will induce high motor voltages on the sensor cable. Conventional temperature transmitters offer no protection from such high voltages, and even though they occur only rarely, they can cause substantial damage to downstream systems and injure people. In addition to “protection under normal conditions”, the EN 60034-1 standard therefore also calls for “protection under single-fault conditions” with a second, matching sufficient isolation barrier. Temperature transmitters, which are functionally required anyway, can conveniently serve as such backup barriers when they conform to standards and are designed to endure high kilovolt stresses. Knick P 44000 temperature transmitters meet both these criteria: the input signal is galvanically isolated and converted into a 4…20-mA output signal. Thanks to their especially robust galvanic isolation, the basic insulation permanently withstands working voltages of up to 6.6 kV AC/DC and, depending on the supply type, can be employed for high-voltage motors with up to 11 kV. Knick's new temperature transmitter thus reliably prevents transmission of high voltage potentials of the motor phase, caused by insulation defects at the sensor. The P 44000 is suited for conventional motor temperatures ranging from 0…150 °C, 0…200 °C and 0…300 °C and features excellent accuracy (±0.5 K) and flexibility (20…253 V AC/DC). It remains fully functional even in conditions with unstable power supply and withstands extreme ambient temperatures from 40 °C to +85 °C.
Illustration: Knick's P 44000 temperature transmitters offer insulation protection for high-voltage motors up to 11 kV.
