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Negative Torque Positive motion


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I plane to Use Power Brick AC in antenna tracker application.


Antenna, under wind action, has to work in 4 quadrant (as in Attachment).


When Wind Force acting in the same direction of the motion, we have motor that works as generator with negative current (and negative torque).


- IGBT-based drives inside Power Brick AC is capable to works in 4 quadrant ?


- If yes, for power Brick Ac used in direct PWM (with output continuos current = 8A rms/axis), which is the negative current limit in continuous duty?


- This negative current is dissipated or returned to the power supply?


thanks for the answer


Odoardo Palazzo


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The Brick AC, like any servo drive, is capable of full 4-quadrant operation. For the power transistors themselves, the continuous and intermittent current limits in generation should be considered the same as for motoring.


The energy from generation mode goes into charging up the bus capacitors, and this will increase the DC bus voltage. When the voltage exceeds a threshold, the "shunt" circuitry is turned on. Current will start flowing through a built-in shunt resistor, dissipating this energy.


The built-in shunt resistor does not have the capacity for heavy continuous use -- it is intended for occasional use, as for a rapid deceleration. If there is a possibility of continuous use, you will probably need to purchase a larger external shunt resistor. Contact tech support for assistance on this configuration.


The Brick AC does NOT have the capability to regenerate this power back to the AC line. That is expensive to implement, and few users would want it.

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