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Sensorless motor control technology in VFDs

The technology is mature, although it is not as easy to implement (and not as widely documented) as other classical sensorless techniques.

High-frequency injection works on a different model than the fundamental one, since the frequencies involved are usually far higher than the nominal one, and suffers from some "reliability" issues (dependence on load, harmonics). This makes it more difficult to implement, at least when the motor to be driven isn't known before.
On the other hand, finding an IPM motor off the shelf isn't that easy, and most of the applications don't require full torque at very low-speed nor position control. If the market doesn't ask, the manufacturers (apart from the giant ones) don't offer it.

BTW, the problem we've found testing the A1000 (on a non-salient PMSM, so no HF injection) was at startup, which was quite weak (impossible even under 33% braking torque). With IPM motors and HF injection, they declare position control too, but we've never tested the A1000 on IPMs.

We implemented high frequency injection for low-speed control a few times. It's a little complicated, but not that big a deal if there is some saliency in the motor (it only needs a small saliency, which can be designed into even PMSM motors without greatly affecting performance). It's really good technology, but you have to be careful what you use it on.

It's not true position control--it only gives you position to within one-half electrical cycle at startup, and you have to then detect which half-pole the motor is in. So there is some possibility of uncontrolled motion right at startup. It's great, though, for loads with either very high inertia or very high ripple torque.

I think the reason why industry hasn't really latched onto it is because (unless you are using an IPM with a single large saliency) it really requires good knowledge of the particular motor saliencies, so it's not much use for general-purpose variable frequency drives (IPMs are not popular in general-purpose applications). However, for specific-purpose VFDs, it's very useful.

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