It is currently 22 Feb 2017, 11:43
Robert wrote:So is this thing not a manual star-delta starter?
Robert wrote:I read it as position A does not latch so returning the lever to A but not keeping hold of it = off.
I did 3 phase theory at ONC and I do remember a fair bit of it. Unlike transmission line theory during HNC electrical and electronic engineering which I've completely forgotten.
9fingers wrote:Looks like a simple star delta and not really worthy of Mr Leonard who provided much cleverer things!
Mark. Make sure that you only use this with motors that are designed for star delta starting eg those marked 700/400 volts.
Reason for one ?? Need was brought about by the
general lack of sufficient capacity of early
distribution systems to start "across the lne " a
large motor on a machine with a high inertia.
The compensator was an early "Soft Start", in
that the first step from the off position was to
manually insert either a transformer or some
value of resistance to ease the starting surge
and limit the inrush current during the period
when the motor was essentially stalled. After the
machine was moving and coming slowly up to speed,
the operating lever on the compensator was moved
to "Run" and full voltage was applied to the
motor.. Later this manual switching was made more
automatic, through the provision of push buttons
and a step timer. If the price is reasonable and
you have a limited electrical service in your
shop,, then consider it's purchase,,, HOWEVER, if
you have to change the motor because of you not
having the right power available for the old
motor (like , you don't have three phase.) then
forget it you don't need it.
More questions ??
9fingers wrote:700 volts ( = approx 400 x root3) is not needed, but would be the natural voltage for full power for a motor that is designed for 400v when in delta.
During starting, the windings are in star but only getting 1/root3 of the voltage and as power is proportional to V squared, the power during starting is about 1/3rd of the normal rated power.
Does that help?
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