SFFS422 May 2022
The PDS/SR is a DC-fed 3-phase inverter which supports the function STO (safe torque off) according to IEC 61800-5-2. The STO function supports IEC 60204-1 stop category 0, resulting in an uncontrolled coast stop too. It shall meet IEC61508 SIL 3 and ISO13849 category 3 PL e.
The STO function removes both supply voltages of the six isolated IGBT gate driver supplies. STO_1 removes the logic input supply (VCC) of the isolated gate drivers, STO_2 removes the input supply (P24V) to the isolated multi-output DC/DC, which therefore removes the isolated output supply rails (VCC2/VEE2) to the six isolated IGBT gate drivers, respectively. Due to that the six outputs of the isolated gate drivers are 0 V (off) and the six IGBTs turn-off respectively. In that case the 3-phase IGBT inverter cannot generate a rotating torque to the motor anymore.
The PDS/SR is operating in high demand or continuous mode, where the rate of demands for operation made on safety sub-function is greater than 1 per year.
| Parameter | Value | Comment |
|---|---|---|
| Safety function | STO | Safe torque off per IEC 61800-5-2 |
| Hardware redundancy (HFT) | HFT = 1 (1oo2) | |
| IEC 61508 SIL level | SIL 3 | |
| ISO 13849 | Category 3, PL e | |
| Demand mode | Continuous | |
| SFF/DC | ≥ 90% (HFT = 1) | Cat 3 PL e medium DC is ≥90%. |
| PFH | < 10-7 | The quantitative analysis is not part of this concept study. |
| STO response time | 10 ms (nominal), 200 ms (maximum) | The Time between active low STO and gate drive output (Vgs) low, which means power IGBTs are OFF. The quantitative analysis is not part of this concept study. |
| DTI (Diagnostics test interval) | 100 ms (10 Hz) | The quantitative analysis is not part of this concept study. Diagnostics runs at least 10 Hz (load switch STO_1 and load switch for STO_2). |
| FRT (Fault response time) | < 200 ms | |
| Mission time (TM) | 20 years | |
| STO input voltage range |
24-V DC ±15% (nominal) +/-60-V DC absolute maximum |
|
| STO input logic level, valid > 2 ms |
15- to 30-V DC: STO function not engaged <10-V DC: STO function engaged |
STO is active low logic input. Input is low-pass filtered to remove OSSD pulses. Valid STO is > 2 ms. |
| Support of OSSD test pulses | Test pulse duration < 1 ms, maximum repetition frequency 500 Hz |
Added low-pass filter to remove (filter-out) the test pulses to avoid trigger STO. Diagnostics for OSSD pulses run at 250 Hz (4-ms rate). |
| DC supply voltage | 24-V DC ±15% (nominal) | |
| Isolated gate driver supply voltages |
Logic supply: 3V3 to 5 V (nominal) Output supply: +15 V, –8 V (nominal) |
It is expected that the supply rails are protected to remain below the recommended maximum operating voltage of the selected isolated gate drivers. |
| Operating ambient temperature | –40°C to 85°C |