AC-PRO-MP-II®, Masterpact Direct Replacement
The AC-PRO-MP-II is a plug-in, direct replacement trip unit for the STR trip units on the Merlin Gerin & Square D Masterpact MP, IEC or UL rated breakers. The AC-PRO-MP-II does not use rating plugs and is user programmable to replace any versions of the STR 18M, 28D, 38S, 58U.
The AC-PRO-MP-II has the same protective functions, settings and time-current-curves as the original STR units.
Front Mounted Test Port
The AC-PRO-MP-II has been upgraded to include a front mounted test port. The new feature makes getting communications setup very easy. The front mounted test port will save valuable time during outages.
Additional Features:
UL and CE Certification 
Utility Relay Company is very proud to announce that the AC-PRO-MP-II now carries the UL and CE Labels. This makes it the only Masterpact replacement trip unit that is UL listed.
Standard trip functions include:
(These will vary depending on the STR type selected)
- Long-Time
- Short-Time
- Instantaneous
- Residual Ground Fault
- Ground Return Ground Fault
- Instantaneous on Closing (DINF)
- Over Temperature Trip
All of the settings are protected by a security code to prevent unauthorized modifications.
Additional Functions:
Sluggish Breaker Detection
The AC-PRO-MP-II now has to ability to detect if the Masterpact breaker is opening slowly and needs service. The first time a breaker opens after a long period of inactivity it may open slowly. This can be caused by mechanical issues, poor lubricant or other obstructions. The AC-PRO-MP-II will capture the sluggish breaker event and display a warning on the screen the next time it is powered up. An external alarm can also be activated when the AC-PRO-MP-II detects a sluggish breaker event.| When the breaker has detected a sluggish opening it will show this alert the next time the AC-PRO-MP-II is turned on. | After the initial warning you can view the actual clearing times. |
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USB Interface for downloading trip history and settings.
The USB interface can also be used to upload settings to the AC-PRO-MP-II. These settings can be loaded from a saved file of settings. Settings and last trip data can also be downloaded from the AC-PRO-MP-II
Programming:
The AC-PRO-MP-II can be programmed one of two ways. The front of the unit has an OLED display that is easy to read in either low or high ambient light. The buttons on the front of the unit are “smart” buttons that change their functions based on the displayed information. The second way to program the AC-PRO-MP-II is using the USB port on the front to connect to a GUI program supplied by URC. The program makes it very easy to commission the AC-PRO-MP-II. The GUI can also be used to view historical data, upgrade the firmware, save the commissioning data and reload the AC-PRO-MP-II from a saved file.
The AC-PRO-MP-II has a mechanical pop out trip indicator on the front of the unit that mimics the functionality of the original unit. There is also a SELF-TEST OK Led, PRE-TRIP LED, QUICK-TRIP switch and an easily accessible LI-Ion battery. The SELF-TEST OK LED indicates a properly operating trip unit. The PRE-TRIP LED indicates a pending trip. The QUICK-TRIP switch activates QT-Instantaneous and QT-Ground Fault settings in the trip unit to reduce arc flash hazard. Connections for a remote QUICK-TRIP switch and indicating light are available. The battery in the AC-PRO-MP-II is only used to power the trip unit to review trip data or change settings when no power is provided from the CT’s. The battery is not used for any of the protective functions of the AC-PRO-MP-II. The battery is also not used to save the last trip data or settings. All of this data is saved in non-volatile memory. The trip unit saves the type of trip, phase and ground currents and date/time for the last 8 trip events. There is also a trip counter that provides the number of trips by trip function.
Online Ordering
Please visit our Kit Ordering Guide page and use the interactive online ordering system to order an AC-PRO-MP-II to replace your faulty Masterpact unit. You can also Contact Us if you need assistance
