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Originally Posted by cts_casemod
V/Hz is just a dumb term that is incorrectly used by manufactures to define a controller with no intelligence of its own.
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OK
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The technical name is scalar control and just derives that for a decrease in frequency one has to reduce the voltage as well to keep the same magnetic flux, which is also true for Field Oriented Control.
Scallar control can be modified to use in a vehicle. Closed loop control, space vector modulation and adaptive output voltage are used to achieve great efficiency.
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The industrial AC controllers I've used have no option for encoder input on V/Hz. You can select a pump load (cubic curve), a fan load (squared curve) or a constant torque load (linear). There is an offset for the voltage to start at 0 Hz, usually called boost. As the frequency setpoint is raised, the voltage output is raised according to the type of load selected. And that's about it for control.
There are also a bunch of parameters for what frequency the boost cuts out, what the starting frequency is, frequencies to skip, aceeleration and deceleration rates, etc etc
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One doesn't necessarily need Field Oriented Control to achieve good performance, although it makes development easier between different motor types.
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No tuning when changing motors is the big advantage. An electrician can change out the motor without calling a tech to tune the drive to the new motor. Paul's version of tuning measures a rotor constant, inductance of the stator ... and something else that I don't remember right now
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Now if by V/Hz you want to say 'open loop scalar control', yes that's pretty much un-driveable on a road vehicle unless the driver has some practice. Its not something nice though.
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OK. Open loop scalar is the term. I learned something today!
I would like feedback to the tach on the dash.
Not sure if it would be undriveable, but it would certainly be different to accelerate or decelerate at a maximum programmed rate each time you change the throttle more than 1% or 2%, until the car is at the 'new' setpoint speed.
I might like to try it, just to see how different it is.