Prophi
®
12R / 12 RS
30
- 29 -
Application
For permanent current monitoring inside the compensation system the MMI6000 is recommended as
an accessory for the controller. This measuring device is able to determine the sum current of the
complete PFC system as well as the current of single capacitor branches.
By monitoring the current of the installed capacitors, extraordinary grid conditions (e.g. harmonic
currents which may cause an overload of capacitors) can be identified. In such a case, the power factor
controller switches off the relevant compensation stages as long as the extraordinary situation
continues. Monitoring of the capacitor current also means monitoring of the capacitor condition
(damages, aging …) and thus gives the opportunity to avoid consequential damages.
The MMI6000 will improve the reliability and safety of a PFC-system.
Method of operation:
The MMI6000 measures the sum current inside the PFC system. For this a current transformer has to be
installed at the power input of the compensation system. During each switching operation, the actual
current change is measured and compared to the rated current of the switched capacitor(s). In
between the switching operations the current of the complete system is monitored.
In case the current of a step is too high (d50%), this step is switched off. The Prophi7 display
shows an inverted capacitor symbol. The current is further on checked periodically is the rated
current reached again, the step is reactivated.
Is the sum current of the complete PFC system too high, stages are switched off one after another and
alarm relay is set. Periodical measurements are performed to check whether the current reaches the
nominal value again. If so, the step is reactivated.
Settings MMI6000:
Settings Prophi 12RS
- Operation mode: Coupling MMI-BR6000
Menu: INTERFACE
- Grid: 3-phase
- 10 Protocol: MASTER-MMI
- 11 Baudrate
- 13 Numbers of MMI
Expert-mode 1:
- 15 C-Test: YES
- 16 C-Error (+150% /-50%)
(setting of switching threshold)
Principle circuit diagram:
CAUTION:
For the bus-connection a shielded cable has to be used!
Bus-connections (in and out) have always to be made directly to the relevant device!
The terminating resistors inside the connected devices have to be activated (DIP-switch ON).
Application: Capacitor current monitoring using MMI6000
consumer
MMI6000
Interface connection RS485
capacitor system with Prophi 12RS
L1
L2
L3
N
Program
Enter
Multi-Measuring
M M I - 6000
Interface
