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TIDM-1003: Number of Current Sense Resistors Needed for Instaspin Motion/FOC

Prodigy 150 points

Replies: 2

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Part Number: TIDM-1003

Hello,

I have been learning about inverter design for BLDC motors. I am very interested in using the C2000 micro-controllers with Instaspin-Motion in a new speed controller. I came across the TIDM-1003 Reference Design and I noticed that document shows three current sense resistors shunted to ground--one for each phase--to monitor the current on each phase. 

Is it really a requirement to have 3 separate current sense resistors? Or can I get by using 1 or 2 current sense resistors? What would be the consequences of doing so? Can I still make use of the C2000 Instaspin motion features? I am asking because I am mostly concerned about minimizing the impact to board space (and I am hoping to make use of an existing FET board that does not have any existing current sense resistors in the paths to ground with as little modifications as possible). Any ideas here?

Thanks,

John 

  • The phase current sensing (using current shunt resistor in TIDM-1003 case) is for current loop control only. It should not affect with your speed loop implementation. If you are interested in InstaSPIN-Motion, please look at TMS320F28069M, which is the only device supports it.

    Do you have alternative method of sensing phase current in our current board design? The method of current feedback doesn't matter and will be able to adapt by modification to code.

  • In reply to Han Zhang6:

    I spent the evening reading the InstaSPIN-FOC™ and InstaSPIN-MOTION™ User's Guide. Section 17 "Shunt Current Measurements" gives a thorough overview of the pro/cons for different current sense architectures and Section 5.2 lists the explicit hardware pre-requisites for InstaSPIN. Pulling from the documentation, 2 and 3 shunt setups are supported in sensorless setups. 1 shunt setups are not supported and 2-shunts are discouraged.

    I think I have the information I need to proceed.

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