Stober SI6A062 - Page 52

6 | Technical data STOBER
52
02/2019 | ID 442728.05
6.3.2.2 Effect of the surrounding temperature
Derating as a function of the surrounding temperature is determined as follows:
§ 0°C to 45°C: No restrictions (D
T
= 100%)
§ 45°C to 55°C: Derating −2.5%/K
Example
The drive controller needs to be operated at 50°C.
The derating factor D
T
is calculated as follows
D
T
= 100% − 5 × 2.5% = 87.5%
6.3.2.3 Effect of the installation altitude
Derating as a function of the installation altitude is determined as follows:
§ 0m to 1000m: No restriction (D
IA
= 100%)
§ 1000m to 2000m: Derating −1.5%/100m
Example
The drive controller needs to be installed at an altitude of 1500m above sea level.
The derating factor D
IA
is calculated as follows:
D
IA
= 100% − 5 × 1.5% = 92.5%
6.3.2.4 Calculating the derating
Follow these steps for the calculation:
1. Determine the highest clock frequency (f
PWM
) that will be used during operation and use it to
determine the nominal current I
2N,PU
.
2. Determine the derating factors for installation altitude and surrounding temperature.
3. Calculate the reduced nominal current I
2N,PU(red)
in accordance with the following formula:
I
2N,PU(red)
= I
2N,PU
× D
T
× D
IA
Example
A drive controller of type SI6A061 needs to be operated at a clock frequency of 8kHz at an
altitude of 1500m above sea level and a surrounding temperature of 50°C.
The nominal current of the SI6A061 at 8kHz is 4.5A. The derating factor D
T
is calculated as
follows:
D
T
= 100% − 5 × 2.5% = 87.5%
The derating factor D
IA
is calculated as follows:
D
IA
= 100% − 5 × 1.5% = 92.5%
The output current of importance for projecting is:
I
2N,PU(red)
= 4.5A × 0.875 × 0.925 = 3.64A