Overvoltage And Trip Levels; Boost - Siemens MICROMASTER 420 Reference Manual

2.6

Overvoltage and Trip Levels

The inverter will protect itself from both supply overvoltage and undervoltage. Trip
levels are shown in Table 2-3. Internal overvoltage can occur during braking
where internal voltages are forced high by energy from an external load.
Table 2-3
1/3 Phase 230 V
3 Phase 400 V
When output pulses are disabled from the inverter an undervoltage trip will not
occur. An overvoltage trip will occur at any time when the overvoltage threshold is
exceeded.
Check to ensure you have matched the input supply to the inverter. If the supply
voltage is too high, you may damage the inverter even if it trips.
2.7

Boost

Boost is used to increase the output voltage in order to overcome losses and non-
linearity at low frequencies. If the correct amount of boost is applied, the current
and torque will be increased at low frequencies. However, if too much boost is
applied, the motor may overheat if run at low frequencies for a long time and
excessive boost may also saturate the motor, leading to loss of torque.
2
The I t function helps protect the motor under these circumstances. Boost is
calculated such that 100% boost is the voltage given by:
Stator resistance (P0350) multiplied by rated motor current (P0305).
Which means that changing the value of these parameters will affect the boost
level.
Voltage
Boost Increases
voltage here
Figure 2-3
MICROMASTER 420 Reference Manual
Issue A1
Trip Levels
205 V
410 V
Frequency
Boost Level
410 V
820 V
11