Fuji Electric FRENIC-AQUA series, User Manual

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Cascade control (Inverter drive motor fixed system)
Configure such a pump drive system that drives a particular pump (M0 in the configuration figure
given below) with the FRENIC-AQUA and drives other pumps (M1 to M8) with commercial power
by turning magnetic contactors ON with the digital output signals issued by the FRENIC-AQUA.
The FRENIC-AQUA drives the M0 under PID control. If the frequency rises due to a PV signal level
drop to satisfy the pump adding conditions, the FRENIC-AQUA outputs pump start signals to turn the
magnetic contactors ON, thereby starting commercial power-driven pumps successively. After
starting all pumps, the inverter can further drive a single auxiliary pump (MA).
If the PV signal level rises and the frequency of the inverter-driven pump drops to satisfy the pump
subtracting conditions, the FRENIC-AQUA cancels pump start signals to turn the magnetic contactors
OFF, thereby stopping commercial power-driven pumps successively.
The number of start signal lines available on the FRENIC-AQUA is a total of six--four transistor
output lines and two relay output lines in a standard configuration, so the FRENIC-AQUA can control
a total of seven pumps (one pump driven by inverter at variable speed and six commercial
power-driven pumps) in a standard configuration.
To operate the pump drive system in a maximum configuration, it is necessary to add the optional
relay output card (OPC-RY2) to the FRENIC-AQUA. It can add seven relay output lines.
The advantage of this system is low cost since the number of controllable pumps is large and the
number of magnetic contactors is one per pump. The disadvantage is large pressure fluctuation since
adding/subtracting of pumps targets commercial power-driven pumps.
The start/stop sequence of commercial power-driven pumps is changeable so that the operating time of
pumps can be averaged.