Canned motor design rotor magnetics

[artis]

Randomly stumbled upon the canned motor , usually used for pumps to avoid a dynamic seal between the pump fluid and atmosphere.
What I cannot understand is this. It is a AC induction motor but the squirrel cage rotor is wrapped inside a sealed metal outer can. On top of that most designs also have a second steel sheet cylinder separating the rotor fluid compartment and stator.
That makes two cylindrical metal sheets between the stator and rotor squirrel cage bars.

So a simple question - how does the rotor bars get any induced current in them at all? Because from what I recall about EM a continual conducting sheet applied to a changing time varying magnetic field causes very strong eddy currents that oppose the applied field.

So what is the trick here? The metal cylinder made from an alloy of poor conductance and thin to minimize the eddy currents or else?

 

[Baluncore]

The metal cylinder made from an alloy of poor conductance and thin to minimize the eddy currents or else?

Yes, thin stainless steel can be non-magnetic and have quite a high electrical resistance.

The rotating field is three-phase, so the effective poles of the rotating field are much larger than the gaps between the stator windings. The eddy current loops are therefore large, so have long peripheral resistive conduction paths.

The currents induced in the sleeve produce a reverse field that only cancels a small part of the rotating field.

 

[artis]

Could it also be that having a 3 phase stator field, the reverse fields and currents produced within the two metal cylinder sleeves that are between the stator and rotor have currents that also cancel one another , at least partially ?

Somewhat similarly how a set of parallel loops that share one common conductor moved across magnet poles all get induced current in the same direction therefore the existence of the common conductor causes current cancellation?

 

[Baluncore]

Could it also be that having a 3 phase stator field, the reverse fields and currents produced within the two metal cylinder sleeves that are between the stator and rotor have currents that also cancel one another , at least partially ?

I think the (rotating) stator field will induce eddy currents in the first sleeve that will partly cancel the incident field in that forward direction. That reduces the magnitude, but does not change the sign of the magnetic field that passes through the first sleeve, to reach the second sleeve, where a similar attenuation occurs again.

If the sleeve was a perfect conductor, the entire incident field onto the sleeve would be cancelled in the forward direction, while all the magnetic field would be reflected back to the field windings.