Beijer Electronics Frequency Inverter BFI-P2
KI00306B 2020-03
www.beijer.se www.beijer.no www.beijer.dk
www.beijerelectronics.com www.beijerelectronics.de www.beijerelektronik.com.tr
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4.5 Derating Information
Derating of the drive maximum continuous output current capacity is required when:
Operating at ambient temperature in excess of 40°C/104°F (IP55 & IP66) or 50°C / 122°F (IP20).
Operating at Altitude in excess of 1000m/ 3281 ft.
Operation with Effective Switching Frequency higher than the minimum setting.
The following derating factors should be applied when operating drives outside of these conditions.
Derating for Ambient Temperature
Enclosure Type
Maximum Temperature
without derating at Switching frequency of 4
kHz
Derate by
Maximum
Permissible
IP20
50°C / 122°F
N/A
50°C / 122°F
IP55
40°C / 104°F
1.5% per °C (1.8°F)
50°C / 122°F
IP66
40°C / 104°F
2.5% per °C (1.8°F)
50°C / 122°F
Derating for Altitude
Enclosure Type
Maximum Height Above Sea Level Without
Derating
Derate by
Maximum
Permissible
IP20, IP55 and IP66
1000m / 3281ft
1% per 100m / 328 ft
4000m / 13123 ft
Derating for Switching frequency
Example of Applying Derating Factors
A 4kW, IP66 drive is to be used at an altitude of 2000 metres above sea level, with 12 kHz switching
frequency and 45°C ambient temperature.
From the table above, we can see that the rated current of the drive is 9.5 Amps at 40°C,
Firstly, apply the switching frequency derating (if any), 12 kHz, 25% derating, 9,5 x 75%= 7,1 A
Now, apply the derating for higher ambient temperature, 2.5% per °C above 40°C = 5 x 2.5% = 12.5%
7,1 Amps x 87.5% = 6,2 Amps.
Now apply the derating for altitude above 1000 metres, 1% per 100m above 1000m = 10 x 1% = 10%
6,2 Amps x 90% = 5,5 Amps continuous current available.
If the required motor current exceeds this level, it will be necessary to either:
Reduce the switching frequency selected or use a higher power rated drive and repeat the calculation to
ensure sufficient output current is available.
Enclosure
Type
Switching Frequency
4 kHz
8 kHz
12 kHz 16 kHz 24 kHz
32 kHz
IP20
N/A
N/A
20%
30%
40%
50%
IP55
N/A
10 %
10 %
15 %
25 %
N/A
IP66
N/A
10 %
25%
35%
50%
50%
