Power Circuit faults like high resistance connections are often found during outages with the motor not running by using precision resistance test equipment like the MCE®. However, we may not have the luxury of an outage and need to identify and determine the severity of a high resistance connection while the motor is running. Can we do it? Yes…
Location, Location, Location…Using Voltage and Current to identify a power circuit fault requires an understanding of the impact of the test lead location. In general, voltage measurements look upstream of the connection location, and current looks both upstream and downstream of the connection location. A high voltage imbalance would result in looking upstream for a high resistance connection or distribution imbalance. A high current imbalance without a voltage imbalance would result in looking downstream for a high resistance connection or motor anomaly. Always compare the impedance and current imbalance values for insight into the likely source being a power circuit or motor related issue. Similar values of impedance and current imbalance indicate a power circuit anomaly where a significantly higher impedance imbalance would lean the troubleshooting toward a motor anomaly.
To see actual data and listen to Todd and Noah discuss a recent power circuit case study with the motor running visit the PdMA YouTube Channel at High Resistance Connection Found Using Online Analysys
