Measuring up to 400A inverter currents in BLDC drive (non invasive measurement)

[zenerbjt]

Dear Engineers,
We are using 10Kw BLDCs fed by 3 phase inverters. We wish to scope the current waveform in the battery supply cables to the inverter. We have selected the MLX91209 current sensor since it gives a non-invasive solution, and our current peaks will be some 400A. One must simply mount it into a gap in a ring torroid, and then run the conductor through that same torroid. The MLX91209 then gives a voltage output proportional to the current. It has the same bandwidth as a current sense transformer, near enough.

https://www.melexis.com/en/product/MLX91209/250kHz-Programmable-Hall-Effect-Current-Sensor

However, the Melexis website doesn’t tell how we can get hold of the SUPRA 50 SP ferromagnetic cores for this useage.
Do you know how much these cost? ..We don’t  yet have a reply from MagLab, the named manufacturer.

[ahbushnell]

I would use a LEM current probe.  Is this to go on a product our just for test. 

https://www.digikey.com/products/en/sensors-transducers/current-sensors/525?k=LEM&k=&pkeyword=LEM&sv=0&pv276=249171&sf=0&FV=1153%7C182102%2C1989%7C0%2C-8%7C525%2C222%7C1131&quantity=&ColumnSort=0&page=1&stock=1&pageSize=100

This is an example.  Not the current number you see is the RMS.  It will measure higher peak currents.  Dig into the specifications.  We use them all the time. 

Andy

[Doctorandus_P]

Have you thought about using (a part of) the cable itself as a shunt resistor?
You will have some drift when the temperature of the copper changes, but HALL sensors are not the most accurate either.

[scrat]

Have you thought about using (a part of) the cable itself as a shunt resistor?
You will have some drift when the temperature of the copper changes, but HALL sensors are not the most accurate either.

That's definitely not a reliable way to measure current. Wonder why so many people in the world uses Hall sensors and expensive shunts...
I warmly second the LEM advice. Plenty of choice, well specified accuracy, bandwidth, etc.
Plus, you can choose the current output type (the most common one), which ensures quite good noise immunity when you bring the output signal through few meters wire (in other words, the typical closed-loop LEM sensors work as 1:N Current Transformers, except they also work with DC).