Siemens MICROMASTER 420 - Avoiding Electro-Magnetic Interference (EMI)

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MICROMASTER 420 Reference Manual
24 Issue A1
2.10.3 Derating with Altitude
Figure 2-15 shows the permissible rated input voltage and output current for
inverter installations from 500 m to 4000 m above sea level.
Permissible rated input voltage
as a percentage of the
nominal voltage
100
90
80
60
70
1000 2000 3000 4000
500 500
Installation altitude in metres above sea level
Permissible rated output current
as a percentage of the
nominal current
100
90
80
60
70
1000 2000 3000 4000
Input voltage
Rated output current
77
Figure 2-15 Derating with Altitude
2.10.4 Derating with Switching Frequency
The default switching frequency of the MICROMASTER 420 is 16 kHz for low
voltage units (230 V)and 4 kHz for high voltage units (400 V). This is usually
adequate for most applications and will allow full performance to be obtained from
all products over the full temperature range.
Select the switching frequency using P1800. High voltage units are automatically
derated by reducing the continuous output current if switching frequencies above
4 kHz are selected. Deratings are shown at P1800 in the System Parameter list.
The switching frequency will be automatically reduced if the internal temperature of
the inverter becomes too high (see r0037, inverter temperature). This reduces
losses and allows continued operation. This feature is controlled by P0290.
Under extreme conditions of overload, the switching frequency may momentarily
reduce to protect the inverter.
The derating applies to constant torque and variable torque settings. Table 2-5 on
Page 25 shows the value to which the maximum outputs are reduced.