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Originally Posted by badfishracing
Is the hardware overcurrent, set by VR1, an actual TRIP/Shutdown, or does it simply cut back the PWM signal?
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As far as I know, it is a hardware detection circuit that disables the MOSFET driver, and it latches the over-current, and it displays a fault code, and you need to cycle power to get the Cougar to turn on the MOSFETs again.
Since it is hardware it is *FAST* ... the output from the current sensor is compared to a reference voltage with a comparator. When the voltage from the current sensor is above the reference voltage, the output of the comparator changes and the MOSFET driver is disabled.
I believe that there is a latch in there, but the micro may do the latching.
I'm a bit fuzzy on the details.
Paul will have to answer whether, under some weird set of circumstances, the High Current Fault would NOT latch, and if it didn't latch, how fast the circuit would enable after the current falls off (since the MOSFETs are turned off) before the MOSFETs are turned on again.
But this would not be normal operation!
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I'm having an issue with a modified, overpowered, PS board. When I hit full amps, 511 as seen on the RTD explorer, it seems to cut way back on power, even through the PWM still says full voltage?
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Modified and over-powered? How are you getting rid of the heat? You need a *LOT* of air moving across the heat sinks to get rid of that much heat.
Heat is proportional to the square of the current. I think that's one of the reasons that electric cars use such high voltages - the power electronics are easier to cool. And the copper wires don't need to be as big. And the contactors don't have to be as big
Is it possible that the modifications messed up the latch on the overcurrent somehow?
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I was running about 1250 amps (seen as 511) at only 50% PWM, for about one second, then power fell off, PWM showed 100%, but it felt like about 25% power.
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The PWM does not need to be very high at low revolutions to draw high amps. If the back EMF from the motor is low, lots of current can flow. But I guess that's why you built that DC Monster Controller!
What you describe sounds more like a heat issue to me. As the MOSFETs pump the amps, the temperature sensor gets hot, the PWM is limited to reduce the heat .. that sort of thing. I don't know where in the code (before or after the display section) the PWM is backed off.
*BUT*... there are others on this board who have hands-on experience with the Cougar and will give you a better idea on what to chase.
These are only my opinions, after all. I don't have an operational original Cougar 500A (although I did KILL one)