Blown talon srx modules

[s1900ahon]

Originally Posted by daneelshof

Manually rotating the motors does generate current and can fry motor controllers. We have fried many Victors and Jaguars this way. We have adopted the following "rule" because of this:

Pushing a robot turns motors which generate voltage, and that voltage is passed through the motor controller's MOSFETs to the battery terminal which subsequently can power the robot. The current path from M+/M- to V+/V- in the motor controller is done through the MOSFET's reverse body diode and they act as a rectifier.

You don't want to pass current through these diodes since they're not intended to pass significant current (they're parasitic), and when they do pass current through them, the power dropped across them is the forward diode voltage times the current. This is why the Black Jaguar, Talon SR, and Talon SRX use synchronous rectification (SR) when driving the motor. SR turns the low side of the H-Bridge on during the "off" phase of the drive. Unfortunately, when pushing the robot motor controllers are not doing SR.

When testing Black Jaguars, the team used a test bench with two CIMs, the output shafts coupled to each other through an AM ToughBox. One CIM was driven from the motor controller and the other used as a generator with the leads connected across a switchable bank of 1 ohm power resistors. You'd be surprised at how much power you can draw out of a CIM when the shaft is turned.

[MrForbes]

Originally Posted by s1900ahon

You'd be surprised at how much power you can draw out of a CIM when the shaft is turned.

I would expect it to be similar to the amount of power you can draw out of the shaft of a CIM when you apply electrical power to the wires.

[Ether]

If P2 is the maximum mechanical power you can draw from a CIM's output shaft for a given input electrical power P1,

and P3 is the maximum electrical power you can draw from a CIM whose output shaft is being driven with mechanical power P2,

then P3 is considerably less than P1.

Reason: motor losses work in both directions.