QUALITROL AKM345 GEN3 OTIWTI
TM
Instruction Manual
40-08847-00-Rev001
www.qualitrolcorp.com
Page 8 of 34
2.2
Operation
The AKM345 operates using a bellows type technology. A temperature probe is installed in a pocket/well located
in the transformer wall or cover. The probe is connected to a sealed system capillary filled with oil that is then
connected to the bellows system in the enclosure of the unit. As the temperature of the oil in the probe
increases, the oil expands also expanding the bellows and as a result driving the dial of the unit along with
switches and remote outputs.
On WTI units, the load current from the bushing CT can be brought directly into the enclosure of the AKM345 to
be used for simulating winding temperature. Winding temperature is simulated from a heater located in the
bellows of the unit providing accurate and reliable gradient indication.
The switches can be used for cooling control and alarming. The remote outputs can be used to transfer data to
a local or remote monitoring system.
2.3
Calibration Check
Each AKM345 instrument is factory calibrated and no further calibration is required.
If the calibration of the AKM345 needs to be verified, please follow the below procedure:
•
Place the probe in bath of boiling water (100°C) or a calibrated oil bath set to 100°C
o
note, the minimum volume of water or oil should be 5 liters!
•
Stir the contents of the oil/water bath to ensure even temperature distribution and check that the
temperature of the bath is 100°C (check with a calibrated thermometer)
•
Read the temperature on the device thermometer after 15 minutes
If the difference between the temperature indicated by the AKM345 unit and the temperature of the
bath is greater than 5°C we recommend contacting Qualitrol for further assistance
2.4
Winding Simulation
The AKM345 GEN3 OTIWTI
TM
has a method to simulate the temperature of a winding by indirect measurement
called thermal image. This is a frequently used simulation method that senses top oil temperature and biases
the thermometer reading proportional to transformer load to indicate winding temperature.
On WTI units, the load current from the bushing CT can be brought directly into the enclosure of the AKM345 to
be used for this method of simulating winding temperature. Winding temperature is simulated from a heater
located in the bellows of the unit providing accurate and reliable gradient indication.
On the AKM345 a matching resistance is used to adjust the current needed by the heating element to provide
the required winding hottest spot (WHS) temperature gradient delivering a parallel path to divert part of the
total current. There are 3 internal matching resistance models (TD50, TD76, and TD50/5) and 2 external matching
resistance models (AKM 44674 and AKM 44678).
2.5
Switches
