astra_conv:conversion:isolation_check:isolation_check
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astra_conv:conversion:isolation_check:isolation_check [2014/03/15 00:12] richard |
astra_conv:conversion:isolation_check:isolation_check [2014/04/29 11:06] (current) richard |
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| The tap inputs can be seen at the bottom left of the diagram. Each of the two yellow tap wires also has an additional 22k series resistor close to the tap, for safety reasons. The two LCA110 solid state relays alternatingly connect them to chassis ground, over some more resistors and the two SFH617 optocouplers. With the 56k + 22k series resistors, the total isolation resistance sums up to a total of 100kOhms, which is safely above the required 50k. The LM2903 on the top left derives the control signals for the solid state relays from a sawtooth signal produced by a simple 555 oscillator. | The tap inputs can be seen at the bottom left of the diagram. Each of the two yellow tap wires also has an additional 22k series resistor close to the tap, for safety reasons. The two LCA110 solid state relays alternatingly connect them to chassis ground, over some more resistors and the two SFH617 optocouplers. With the 56k + 22k series resistors, the total isolation resistance sums up to a total of 100kOhms, which is safely above the required 50k. The LM2903 on the top left derives the control signals for the solid state relays from a sawtooth signal produced by a simple 555 oscillator. | ||
| - | If either of the two optocouplers' output transistors gets conductive, the voltage at the low-pass stage below will rise. Another LM2903 will trigger and create the warning signal, if a certain threshold is exceeded. The 555 timer in the following stage will trigger if this condition stays for a few seconds. | + | If either of the two optocouplers' output transistors gets conductive, the voltage at the low-pass stage below will rise. Another LM2903 will trigger and create the warning signal, if a certain threshold is exceeded. The 555 timer in the following stage will trigger if this condition persists for a few seconds. |
| The device has two outputs (active low and active high) for the "isolation check failed" alarm. | The device has two outputs (active low and active high) for the "isolation check failed" alarm. | ||
| + | Front and rear view of the unit. | ||
| + | {{ :astra_conv:conversion:wiring:p1110470.jpg?550 |}}{{ :astra_conv:conversion:wiring:p1110471.jpg?550 |}} | ||
| - | The "isolation check" circuit is continuously powered (i.e. not dependent on ignition). It's function can always be verified by a test button at the rear side of the rear battery box, that simulates a slight isolation fault (see chapter "rear traction battery box" below). | + | |
| + | The "isolation check" circuit is continuously powered (i.e. not dependent on ignition). It's function can always be verified by a test button at the rear side of the rear battery box, that simulates a slight isolation fault (see chapter "rear traction battery box"). | ||
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astra_conv/conversion/isolation_check/isolation_check.1394842334.txt · Last modified: 2014/03/15 00:12 by richard
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