Maintenance Indicators

MicroLogic trip units have indicators for, among other items, the number of operating cycles, contact wear P/H, load profile and operating times (operating hours counter) of the MasterPacT circuit breaker.

It is possible to assign an alarm to the operating cycle counter to plan maintenance.

The various indicators can be used together with the trip histories to analyze the level of stresses to which device has been subjected.

Contact Wear

Each time a MasterPacT circuit breaker opens, the MicroLogic P/H trip unit measures the interrupted current and increments the contact-wear indicator as a function of the interrupted current, according to test results stored in memory. Breaking under normal load conditions results in a very slight increment. The indicator value may be read on the FDM display.

It provides an estimation of contact wear calculated on the basis of the cumulative forces affecting the circuit breaker. When the indicator reaches 100%, it is advised to visually inspect the contacts per the instructions in the circuit breaker user guide.

Circuit Breaker Load Profile

MicroLogic A/P/H trip units calculate the load profile of the circuit breaker protecting a load circuit. The profile indicates the percentage of the total operating time at four current levels (% of circuit breaker In):

• 0 to 49% In

• 50 to 79% In

• 80 to 89% In

• ≥ 90% In.

This information can be used to optimize use of the protected equipment or to plan ahead for maintenance interval extensions.