Monitoring Temperature and Power on Aging 3-Phase Compressor Motors

Single dataTaker Solution Monitors and Totalizes the Data

CAS DataLoggers recently helped a frozen product manufacturer to monitor current/voltage on several large 3-phase compressor motors used for refrigeration. As these compressors aged through valve leakage and piston ring deterioration, the AC temperatures fluctuated which endangered product quality. The motors had to run a high load and maintain a low coil temperature, and their effectiveness could be further strained by low-voltage conditions. To avoid compressor failure and to realize energy savings, the manufacturer needed automated monitoring with a high number of channels that could monitor temperature and the equipment’s current/voltage/energy usage to see how hard the compressors were working. The customer also needed to totalize the energy data and the motor on/off times, so an intelligent solution was needed.

The plant manager installed a dataTaker DT85 in an industrial enclosure secured onto a pushcart so that it could be moved around the factory to test the motors throughout. Over time each 3-phase compressor motor was connected to 6 of the logger’s channels to monitor its current/voltage. Thermocouples were placed on the motors, compressors, and evaporator coils, connected to the logger’s analog inputs. Additionally, 2 pressure transducers were connected to each motor’s inputs, one on the suction side and one on the discharge side. A WattNode Modbus sensor was also connected to monitor the 3-phase equipment to view current/voltage and KWh for power factoring and AC power measurement.

The dataTaker DT85 intelligent data logger supported many communication features including a USB memory stick port, support for multiple SDI-12 sensor networks, Modbus for SCADA systems, FTP and Web interface, 12V regulated output to power sensors, the DT85 offered a flexible solution for monitoring all the required values. Meanwhile the dataTaker’s digital inputs monitored motor runtime.

All measurements were recorded at 18-bit resolution and clearly shown on the logger’s built-in display. The dataTaker DT85’s Dual Channel concept allows up to 32 isolated or 48 common referenced analog inputs to be used in many combinations, enough to allow connection for all the different sensors so that every parameter could be measured. Users could store up to 10 million data points in user-defined memory, log as much or as little as needed with independent control of schedule size and mode, and overwrite or stop logging once the logger’s allocated memory was full. Users could also archive data on alarm event, copy to USB memory or send via FTP.

Along with the logger and sensors, CAS DataLoggers also provided value-added services including FREE technical support to help the customer use the dataTaker’s totalizing capability to calculate the total compressor energy consumed and on/off times. Using the internal channel variables and calculation capabilities of the dataTaker, it was simple to capture cumulative totals as well as to total over a particular period of time such as a day, week or month. 2 types of signals could be totalized: analog signals like a 4-20mA current loop, and digital signals from a switch or pulse output meter. The dataTaker provided built-in functions to automatically integrate measured values.

Users could accumulate these totals since the start of the program or view a daily, weekly or monthly total. In these cases, another schedule within the logger (in conjunction with an alarm if needed) could be used to reset the total. For example, if only a daily total was required, a second schedule could be created to run once a day and within this schedule the CV containing the accumulated total could be set to 0. For other reset intervals, the data logger also provides an internal channel for the day of the week (4ST) along with system variables for the day of the month (20SV) and day of the year (21SV). These can be used in an alarm statement to reset the channel variables containing the totalized data via the Action Command.

The dataTaker served as a single solution for monitoring the customer’s 3-phase compressor motors and serving as an early detection system before the compressors could suddenly go down. The data logger’s large number of universal analog inputs connected to all the needed sensors to give users the total picture of their machine data, and the dataTaker’s Modbus capability allowed connection to the WattNode Modbus sensor. The DT85 logger was also useful for identifying equipment and power issues. The dataTaker had additional uses whenever the business had to retrofit its motors and compare energy usage before and after replacement to get an accurate before and after picture of the cost savings.