944U Datasheet, PDF (3/4 Pages) Cornell Dubilier Electronics – High Current, Low Profi le for Inverter Applications

Type 944U Polypropylene, DC Link Capacitors
High Current, Low Profile for Inverter Applications
Expected Lifetime Predictions
Capacitance: C (µF)
Equivalent Series Resistance: ESR (mΩ)
Frequency: f (kHz)
Ripple Current:
Ambient Temperature:
Core Temperature:
Total Thermal Resistance:
I (A_rms)
T_A (°C)
T_C (°C)
Θ (°C/W)
Thermal Resistance case-to-ambient: Θ_CA (°C/W)
Thermal Resistance core-to-case: Θ_CC (°C/W)
Airflow Speed: v (m/s)
Applied Voltage: V_A (V_DC)
Rated Voltage: V_R (V_DC)
Determine ESR at Operating Frequency
Use the 10 kHz ESR from the ratings tables.
For operation below 10 kHz, the ESR will need to be adjusted using the following
equation: ESR - 31.83/(10C) + 31.83/(fC).
Determine Thermal Resistance at Operating Frequency and Air Flow
Compute Θ = Θ_CC + Θ_CA. In the ratings tables, Θ_CA is for still air. For v = 0 to 5 m/s,
multiply Θ_CA by [(5 + 17.6(0.1^0.66)) / (5 + 17.6(v + 0.1)^0.66)]
Determine Expected Lifetime
Look up Expected Lifetime on the graph using V_A/V_R and T_C = T_A + I² (ESR/1000) Θ
The maximum allowed temperature rise is 40 °C and the maximum allowed core
temperature is 95 °C.
Expected Lifetime vs Hot Spot Temperature and Applied DC Voltage
1.6
1.5
1.4
50ºC
1.3
60ºC
1.2
70ºC
1.1
1
85ºC
0.9
0.8
1000
10000
Expected Lifetime (h)
100000
1000000
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