View Single Post
Old 11-03-2015, 04:12 PM   #2279 (permalink)
e*clipse
Permanent Apprentice
 
Join Date: Jul 2010
Location: norcal oosae
Posts: 523
Thanks: 351
Thanked 296 Times in 213 Posts
Quote:
Originally Posted by MPaulHolmes View Post
Do you mean the PWM1H, PWM1L, ..., etc? Or do you mean other pins? All the other pins were semi-random, and mechanically convenient for routing.
Thanks - I was referring to the pins on the logic gates - for example PWM1L being connected to U11b with the output PWM1L_AFTER_FAULT

I was wondering why it's neighbor on the logic IC, for example is PWM2H. You've cleared that up - thanks!

Regarding the current sensing, I've found some more info that helps with shielding around the Melexis current sensors. The info looks pretty sophisticated, with magnetic FEA programs, etc. However, I think we can use some simple rules of thumb to make a make useful shields for this purpose. A company in Switzerland sells them, but they look pretty easy to make.

http://www.google.com/url?sa=t&rct=j...GTfNDbdnEHSrtQ
http://www.google.com/url?sa=t&rct=j...KPGO3xU1WmRewA
http://www.maglab.ch/uploads/media/UCR3.5-T-2.jpg
http://www.maglab.ch/uploads/media/2..._rev003_01.pdf

The bottom line from the first link is that magnetic cross-talk between the 3 phase output channels can hurt the current sensing accuracy. Completely wrapping the wire in a rectangular shield actually didn't help the sensor. However, a U-shaped sensor - like the ones shown on the Melexis data sheet - both straightened and enhanced the magnetic field for the sensor and shielded the magnetic field from other stuff. So if the simple rule of thumb guidelines on the Melexis sheet are followed making a shield should be NBD.

There seems to be no maximum length. So, for the round inverter design, a shield that extends from the circuit board to the top cover would serve the dual purpose of shielding the controller stuff from the magnetic fields in the output wires and focus the fields for the current sensors.

- E*clipse
  Reply With Quote
The Following User Says Thank You to e*clipse For This Useful Post:
MPaulHolmes (11-03-2015)