Siemens SINVERT 350 Maximum Power Point LED MPP, Standby operation LED Standby, Fault display

Hardware operation

3.2 Operating the inverter

Maximum Power Point (LED "MPP")

The power which can be generated by a PV system depends on the level of insolation and the temperature of the PV modules. The inverter control unit is equipped with a "Tracker" which automatically tracks the MPP (Maximum Power Point) of the PV field in Automatic mode. As soon as the inverter tracker has found the MPP, the LED "MPP" lights up.

A flashing "MPP" LED indicates throttling of the inverter due to overtemperature of the cooling element.

Standby operation (LED "STANDBY")

The LED "STANDBY" lights up if the power unit of the inverter is switched off, but the control electronics and control panel are switched on (for example, if the PV field output is not sufficient to compensate for the losses, or if the inverter has been switched off manually). The AC contactor is open, and the DC contactors are open, closed or switching between these two states (in order to check whether sufficient voltage/output is available to start operation).

Automatic mode / Test mode

The LEDs "AUTO" and "TEST" indicate the current operating mode of the inverter.

Line (grid) status (LED "LINE OK")

The inverter is equipped with a monitoring unit for the three-phase AC grid. This can detect grid faults or failures. If a fault is detected, the inverter shuts the system down to prevent the regeneration of hazardous voltages to the grid. The LED "LINE OK" indicates that the grid voltage and frequency are within the programmed limit values.

3.2.10 Fault display

If malfunctions in the PV installation develop which affect only certain parts of the system and do not prevent it from regenerating energy to the grid, operation continues and the inverter triggers an alarm. If a malfunction develops which affects the entire system, the inverter is switched off with a fault message. The LED "ALARM" flashes to indicate an alarm.

The LED "FAULT" lights up steadily to indicate a fault.

3.2.11 Numerical display

In Automatic mode, the output of the whole PV system as a percentage of rated output is shown on the two-digit display. If the output is more than 99%, a value of "00" is displayed. At the same time, the LED ">100%" lights up in the grid indicator bar.

In Test mode, the two-digit display shows the first two digits of the set DC voltage value (for example, 55 represents a voltage of 550 V DC).

Codes for malfunctions

In the event of a fault or alarm (in Test or Automatic mode), a corresponding code appears on the display. The meaning of these codes can be found in table 4-1. The code will remain displayed until the operator resets the alarm or fault by means of the keyswitch.

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