This is a work in progress…..
Warning – not all terms are technically correct. I am certain someone will put me straight.
Here we go…
Take one small 4 pole (1330 ! RPM) 3 phase induction motor. Nominally 415V 50Hz connected in star. (Out of the skip bin. Working perfectly. Right price !)
Original rating 0.37kW ( 1/2hp), now make it deliver 1.5kW continuous / 4.5kW peak at 6000 RPM (less some increased losses)
How ?
Open it up. Identify the coils / wiring and re-arrange so emotor is wired for 104V. Then run it at v/f ratio of 2, up to approx 415V.
Put it another way…. Make it into a 200Hz emotor.
Ok, giving the insulation a hard time maybe !
It will make it non ‘off the shelf industrial’ for the purists but it may address our present v/f limitation on industrial AC induction motors without doing a rewind $$.
The victim...
The emotor and full coffee cup. Stator in emotor body only shown. Rotor, bearings and end caps already removed.
Nameplate 415V in star. ( It would also connect as 240V in delta.)
Existing wiring after I cut some of the tie down cords to free the wiring.
Note the interphase insulating paper, normally expected for VFD work. Tick.
Identifying the stator segments pole pitch.
Here is the coffee inspired sketch ! (actually more than one cup required). Just for me to follow you understand. You guys all know this gear.
24 segment so pitch is 6 segments per pole. 4 poles (2 pole pairs) N.S.N.S.
Terminal block.
Shorting bar goes across top 3 terminals for star and vertically over each pair for delta. Normal 3PIM connections.
Freeing up the inter coil wiring that has high temp woven fibreglass sleeving on it.
Starting the wiring cuts. Fortunately this emotor has minimal varnish splashed over the wiring so it is easy and non destructive to pull the wiring free and no damage to the enamel on the copper wiring.
There are 4 coils per phase ( in series) x 3 phases = 12 coils in total. The coils are quite separate items.
The plan is to re-connect these series coils all in parallel (observing phase). i.e. 1/4 voltage (415/4 ~ 104V in star) ( 60V in delta)… could also arrange for 1/2 voltage, but then ….go for broke ! (My Danfoss says it will run a motor down to 50V)
I played with this using clip leads and a DC power supply. Seems to make sense so far.
Screwdriver probes flux in each segment to locate coil positions when 12V DC passed through each coil. I should use a P.magnet to confirm polarity as well.
This all leads to thoughts of modifying Red Suzi's emotor.
Ok, so tell me it has all been done before. Tough.

Anyone interested in this ? Shall I post any more of this experiment ?