Quote:
Originally Posted by nlc
In my opinion, the real reason to use 3 sensors on big controller is because the current sensor price is really low compared to the global controller cost, thus it become really interesting to completely protect the third phase semiconductor too.
Because with 2 sensors, the 3 phase outputs can be short circuit protected between each other, but only two of them are short circuit protected between phase and +vbus ou gnd. With the third phase current, all phase can be completely protected (short circuit with an other phase, vbus ou gnd)
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I think that what Paul said is that he's measuring 2 currents at the same time and that this is enough information.
Perhaps I should describe what I think the measurements can do and then you can correct that. I must have something messed up here.
- the hall effect current sensors are on the three output phases, after the IGBTs
- phase to phase issues can be detected in the motor by comparing phase currents
- phase to ground issues can be detected in the motor by having the currents not add to 0
- V+ to V- cannot be detected, since the sensors are isolated from the bus by the IGBTs?
- V+ or V- to ground cannot be detected, since it is not a complete circuit?
- measuring 2 currents gives most of that protection but you have to do some math
Where did I go wrong?