Re: hi-freq motors[perske etc]

>--- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:
>
> Yikes! This is pretty scary. There are still some other things to
>look
> at. The thickness of the laminations is determined by the eddy
>losses,
> and that needs to be made thinner for higher frequencies. You did
>note
> this was a fairly small motor, so it is a little less likely to go
>boom.
> The motor shop may have selected a motor that had a more robust
> design than some others. Unless they have made it to run at much
>lower
> flux levels (lower torque, too) than the original motor, I can't
>see how
> they can get away with such a large frequency increase without
>smoking
> the stator. I just worry that something bad is going to happen
>someday,
> and somebody is going to get hurt. Even a piece of the integral fan
> flying off could be lethal.
>
> Jon

Jon,
I think you are missing one relevant point here. These rewinders have
been doing this for ages. In fact I just rang them [8.55am in UK
here ] and asked the father of the guy who currently runs the job how
long and how many they had done. Answers were over 25 years and
totals must be between 100 and 200.
This neck of the woods we live in is renown for chair frame
manufacture. Even today with cheap imports there must be close to 100
of these samll firms in a 4 town area. All running the same machines
so there are loads of these big high cycle motors around here. There
are 22 firms within a 3 mile radius of where I sit.
Not only that but there are three companies doing rewind work all in
this small area.
Perhaps with the different geographical operation betwen the UK and
the US your motor rewinders don't or can't be bothered to investigate
this. Or perhaps it's that the customer base is spread so wide it's
not worth the effort.
I suspect the latter as a friend in Arizona with a bed mill had a
Baldor servo motor go down. Baldors wanted $1100 for a new motor and
3 weeks deliver. No one in AZ was prepared to rewind a servo with
tacho. Nearest place he could find was in TX. $300 and 3 weeks turn
round. $600 for a 3 day turn round plus carriage both ways.
I had a spare motor here same model, good tacho, bad armature. Had it
rewound, one day $200, shipped out guaranteed next day from the UK to
AZ by Fedex, $170 so within the three day period he was back up and
running at half the cost.

John S.