Calculation example – discharging circuit
Calculating an active discharge for the quad inverter by using of 3 watts of power resistors.
5 capacitors (each 15 µF) are connected in parallel for each inverter.
The discharge circuit should be activated with a normally open switch contact, if the HV circuit or the battery is disconnected.
Calculation example:
| Uo | = | 600 V | Uo | = |
HV battery voltage (DC circuit voltage) |
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R1, R2, R3, R4 |
= | 150 kOhm | R | = | Discharging resistance (predefined) |
| C | = | 300 µF | C | = |
DC circuit capacity (5 x 15 μF x 4 inverters) |
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Total resistance |
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Discharge current |
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Maximum power loss all resistors | |
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Maximum power loss each resistors | |
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Time constant |
Discharge time to prescribed residual voltage Uc
| Uc | = | 50 V | Uc | = |
Residual voltage at capacitor |
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ln |
= |
Logarithm naturalis |
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| Discharge time in seconds until residual voltage Uc is reached | ||
| Discharge time in minutes until residual voltage Uc is reached |
Result:
With active discharge according to the calculation example a discharge time of 111.821 s (1.86 min) is needed, to be discharged to a residual voltage of 50 VDC.
Residual voltage to prescribed discharge time t
| t | = | 300 s | t | = |
Discharge time |
Result:
After 300 s discharge time, the residual voltage is 1 volt.
