The Haiti National Reference Laboratory and The United States President’s Emergency Plan for AIDS Relief (PEPFAR) Program are expanding and improving the health facility laboratory infrastructure throughout Haiti. The success of this effort is highly dependent on the provision of stable and reliable electricity to these labs to support increasingly sensitive laboratory equipment being deployed throughout the country.
Haiti is plagued with unreliable electricity in both quantity and quality. Where the grid exists, it is often not energized. When it is energized, the quality of electricity in the lines is poor and cannot support lab equipment. Additionally, many health centers in the country are not even served by the electrical grid. This situation has led many health system providers in the country to take action for providing clean and reliable power to their equipment.
A key action that is seen widely throughout the country is the installation of inverter / chargers, and battery banks to provide utility back-up. These systems are installed with and without generators; as well as with and without solar panels. The inverter / charger / battery bank equipment forms the core of a variety of on-grid and off-grid power solutions.
The Xantrex model SW 4048 is a power management center that includes a DC to AC inverter, an AC to DC battery charger, a transfer switch between using AC incoming power or battery power, a transfer switch to choose between two different AC sources, relays to perform a variety of user-selected functions, and a computer with an LCD screen and user input for customizing most of the variables.
The SW can be connected into an electrical scheme in many different ways, but some common elements remain unchanged from installation to installation. The overriding purpose of the SW is to provide continuous power to the loads (AC OUT). If there is power (with the proper characteristics) at the AC IN terminals, then the equipment will utilize this power to feed the loads (AC OUT) and charge the batteries through the built-in battery charger.
When power is lost to AC IN, the on-board computer switches the transfer switch so that the AC OUT loads are fed from the battery through the DC to AC inverter, and the inverter is turned on. This happens nearly instantaneously. When this situation occurs, the entire load is being powered by the battery bank. Of course, this cannot go on forever, and when the battery bank reaches a programmed low state of charge (depicted by low voltage), the system turns off.
The SW model inverter/charger includes provisions for two AC Inputs. Field visits did not reveal any field application where both inputs were used. In many cases, both inputs will not be needed, but there are many applications where they would be useful. The basic system diagram changes only at the AC IN provisions, where a second transfer switch is added that selects between two possible inputs.
The SW includes provisions for programming and customization of the system. Menu 9: Inverter Setup allows the user to configure the inverter settings, including the maximum current flow on each of the AC IN 1 and AC IN 2 terminals. Menu 10: Battery Charging allows the user to configure the battery charging settings, including the charging voltage and current. Menu 11: AC Inputs allows the user to configure the AC input settings, including the maximum current flow on each of the AC IN 1 and AC IN 2 terminals.
The SW also includes provisions for operation and maintenance. The system includes a daily log that records the system’s operation, including the number of hours the system has been running and the number of times the system has switched to battery power. The system also includes provisions for battery maintenance, including equalization and depth of discharge monitoring.
Common problems that can occur with the SW include power quality problems and voltage window issues. The system can also experience load management and battery management issues. The system includes alarms and warning systems to alert the operator of impending cut-out and other issues.
In conclusion, the SW is a powerful and flexible power management center that can provide continuous power to loads in a variety of applications. The system includes provisions for programming and customization, operation and maintenance, and troubleshooting and repair. With proper installation and maintenance, the SW can provide reliable and efficient power to a wide range of applications.