I feel certain that you will agree that the subject of this thread.....ie, a BLDC pump for pumping water (a constant load) at a fixed speed of (only ever) 8000RPM is a relatively simple task...but there are no controllers on the market that do this...why is this?
So, Why are simple Fixed Speed Pump Controller IC’s for BLDC pumps not available?
If we wish to pump water to our irrigation system, and we wish the BLDC pump motor to only ever spin at 8000RPM, then this is a fairly simple situation (compared to the requirement for a motor with a requirement to change from one speed to another very quickly whilst laoding might be constantly varying widely).
Why are simple BLDC motor controller ICs for fixed speed pumps (obviously fixed load aswell since they simply pump water at constant speed) not available?
Surely, all that is needed is a controller which …
1….First Aligns the motor into a known position..
2….then Slowly ramps up the bridge transistor switching frequency till the frequency necessary to give 8000RPM has been reached
3…..Then in-built back-EMF sensing could lock the motor coil pulses to the back EMF signals (sensorless control of BLDC) .
..there’d not even be any need to vary the commutation on time of the bridge transistors away from maximum at any stage, since an upstream SMPS could simply be controlled to supply whatever current the motor required to be able to spin at the required RPM?
..as such, you wouldn’t even need to use the BLDC Bridge driver to limit the current in the motor coils.
Why don’t off-the-shelf controllers, with such a simple modus operandi, exist anywhere in the world?