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OPA541: How to Drive a Three-Phase Star-Connected Motor Using Power Operational Amplifiers

FAZHI LIU
Prodigy 30 points
Part Number: OPA541

Tool/software:

I would like to inquire about the method of driving a three-phase star-connected motor using power operational amplifiers (op-amps). Specifically, I am concerned about the lack of a common ground signal in the outputs of the three power op-amps. Is there a return path for the current? My understanding is that power op-amps, unlike PWM drivers, cannot directly handle reverse current. Could you please provide a wiring diagram for connecting three power op-amps to a three-phase motor?

  • 0
    TI__Genius 14446 points

    Hey Fazhi,

    The power amplifier can drive a motor very similar to a PWM driver. If anything, the power op amp may be better suited to absorbing reverse current as the op amp is a four quadrant output device. 

    In terms of reverse current, the device will attempt to maintain low VID across the inputs by sinking or sourcing the required current. This hold true until we exceed the current capacity of the device.

    The heavy inductive loading of the motor can often cause "kickback" if the power amp is turned off while the motor is still operating. In these cases, external protection diodes may need to be installed at the output of the power amp to offer more protection against fault conditions. 

    When I hear three-phase motors I often think of AC induction motors (very large industrial motors). What size motor are you planning to test, is it a BLDC motor?

    You are using a star connection right? This means you will have an optional neutral point you could reference to. If you were using a delta connection, you would not have access to this fourth terminal. 

    The return currents do not need a common GND so long as all motor phases are similar impedance. 

    Thanks,

    Jacob