On 10/11/10 03:00, dennis wolfe wrote:
>
>
> Very noticeable grinding noise from the motor during the first few
> revolutions of start-up. More apparent with a very slow application
> of throttle. This wasn't objectionable either as it only happened for
> < one second at start-up.
>
This seems to be a characteristic of the technology - in 'traction'
applications (e.g. French built VAL metro/people mover trains - rubber
tyred automatically driven things), I noticed a very pronounced 'grind'
when the trains started to move. And it wasn't a particular build
either, I noticed it on 3 different VAL technology equipped systems on
different models of the rail cars.
(OK, my 'first' hobby is being an electric transit nut, not an electric
boater :-)
I assume for a few seconds from a standing start, the 'rotating'
magnetic fields are rotating faster than the motor core and it's
'slipping'. Once things start to actually move, the motor 'syncs up' and
becomes virtually silent.
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