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Old 06-07-2011, 05:18 PM   #4853 (permalink)
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Originally Posted by ianbartie View Post
Would would mind detailing how you got the motor amps up t0 625?
Here's a bit more detail on increasing the current:

VR1 adjusts the current trip level for the hardware overcurrent protection circuit only. The AVR micro sees the output from the HASS sensor directly without any scaling.

You have two options. One is to replace the HASS 300 sensor with an HASS 500. That will give you 500/300 = 1.66 * 500A = 833A. That is without any software change.

The other is to modify the software and keep the HASS 300 with VR1 turned to max for 775A. This will allow you maybe 700A as the PI loop that controls current does not work correctly if there is not some margin between the current it regulates and the hardware overcurrent trip point. The software modification is quite easy.

For the firmware cougar-v1.11b

In cougar.c, line 322 we have:

current_fb = (loc_current_fb * 19) >> 3; // (19/8 is 2.375)

This scales raw counts from the LEM current sensor to amps.
If you simply change the 19 to a 15 you will increase the raw counts required by a factor of 19/15 to achieve the same amps count.
Since the controller now puts out 509A, 509*19/15=644, so 644A.
If you change it to .... *31)>>4 then the current will be 625A

Note that the serial output to RTD Explorer will be wrong, as I mentioned previously.

The thing ought to be able to handle quite a bit more yet as the MOSFETs are rated at 130A each and there are ten of them. The diodes I think from memory are only 50A x 20 = 1000A, so there is a fair bit of safety margin. Might be interesting to take it up to 700A and see.
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