Service manual

990-1008, Revision 1, 4/995
BOOST/BUCK CONVERTER
Function: The boost/buck converter controls the power factor and regulates the input current. The
boost/buck converter makes up for any difference between the output of the Smart-UPS DP
and the mains voltage. The boost/buck converter is an electronic choke and works as such.
Therefore, the boost/buck converter has a huge internal resistance. Contrary to this, the main
inverter is controlled as a constant voltage generator and has, therefore, a very low internal
resistance. Together these two inverters protect the load against mains transients. They also
protect the mains against harmonic reflections from the load. The control of the boost/buck
converter ensures that the unit is always drawing a sinusoidal current from the mains
MAIN INVERTER
Function: During mains operation, the main inverter is always synchronous to the mains and works as a
voltage stabilizer on the output voltage. If the load causes harmonic current on the output, the
main inverter will support these currents, hence the control of the boost/buck converter
prevents them being taken from the mains. The main inverter helps charge the batteries by
passing the turned over energy from the input to the batteries. During battery operation the
main inverter supplies the load with energy from the batteries. During battery operation the
main inverter is kept at the desired frequency by means of the internal clock frequency.
BATTERY
Function: The battery stores energy to be used during battery operation. All units have built-in batteries.
The batteries are located in the bottom of the unit. More batteries can be added to increase the
back-up time.
OUTPUT CURRENT SENSOR
Function: The Output Current Sensor is used to measure the output current in order to indicate if the
system is overloaded.
SYSTEM OUTPUT
Function: Ensure safe and proper connection of the load.
This is the output of the Smart-UPS DP