12.5. Derating Information
Derating of the drive maximum continuous output current capacity is require 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
12.5.1. Derating for Ambient Temperature
12.5.4. Example of applying Derating Factors
A 4kW, IP66 drive is to be used at an altitude of 2000 metres above sea level, with 16 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), 16 kHz, 0% derating
Now, apply the derating for higher ambient temperature, 2.5% per °C above 40°C = 5 x 2.5% = 12.5%
9.5 Amps x 87.5% = 8.3 Amps
Now apply the derating for altitude above 1000 metres, 1% per 100m above 1000m = 10 x 1% = 10%
8.3 Amps x 90% = 7.5 Amps continuous current available.
If the required motor current exceeds this level, it will be necessary to either
- Reduce the switching frequency selected
- Use a higher power rated drive and repeat the calculation to ensure sufficient output current is available.
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