Altitude derating: The derating factor for 1500 m is
.
The derated drive output current becomes
Surrounding air temperature derating: From the table, the derating factor for 55 °C
surrounding air temperature is
The derated drive output current becomes
Example 1, UL (NEC): How to calculate the derated current
Drive type is ACS480-04-014A-4, which has drive output current of 14 A. Calculate the
derated drive output current (I
N
) at 4 kHz switching frequency, at 6000 ft (1829 m) altitude
and at 131 °F (55 °C) surrounding air temperature.
Switching frequency derating: From the table, no derating is needed at 4 kHz.
Altitude derating: The derating factor for 6000 ft is
The derated drive output current becomes
Surrounding air temperature derating: The derating factor for 131 °F surrounding air
temperature is
The derated drive output current becomes
Example 2, IEC: How to calculate the required drive
If your application requires a nominal motor current of 6.0 A at 8 kHz switching frequency,
the supply voltage is 400 V and the drive is situated at 1800 m altitude and at 35 °C
surrounding air temperature, calculate the required drive size.
Altitude derating: The derating factor for 1800 m is
.
Surrounding air temperature derating: No derating needed for 35 °C surrounding air
temperature.
To determine if the derated current of a drive is enough for the application, multiply the
nominal drive output current (I
N
) by all the applicable derating factors. For example, drive
type ACS480-04-12A7-4 has a nominal output current of 12.6 A. From the table, the switching
frequency derating for this drive type is 0.68 at 8 kHz. Calculate the derated drive output
current:
Technical data 99
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