Motor wiring's weird term question.

[melon]

Hi!
When it comes to electrical motor connection wiring what does "all voltage"
term mean? I found it as an alternative wiring for "star-delta" in the motor
controller's manual (no drawings, no explanations).

Thanks!

 

[daestrom]

Hi!
When it comes to electrical motor connection wiring what does "all
voltage"
term mean? I found it as an alternative wiring for "star-delta" in the
motor
controller's manual (no drawings, no explanations).

Haven't a clue. Never heard *that* term.

But "Full Voltage" is sometimes used to describe a motor starter. Rather
than connect the motor to "reduced voltage" for starting to limit the
in-rush, the motor is immediately placed directly across the line.

Is it possible the question was asking about a motor starter circuit and not
just the motor??

daestrom

 

[melon]

Haven't a clue. Never heard *that* term.

But "Full Voltage" is sometimes used to describe a motor starter. Rather
than connect the motor to "reduced voltage" for starting to limit the
in-rush, the motor is immediately placed directly across the line.

Is it possible the question was asking about a motor starter circuit and not
just the motor??

1st of all, thanks for your reply!
Yes, it actually is starter circuit wiring issue. I found that it's possible
to wire control circuit 480 or 480/277, so the first configuration is
aformentioned "all voltage", the second "delta-star", hope I'm not wrong.
Thanks once again.

 

[daestrom]

1st of all, thanks for your reply!
Yes, it actually is starter circuit wiring issue. I found that it's
possible
to wire control circuit 480 or 480/277, so the first configuration is
aformentioned "all voltage", the second "delta-star", hope I'm not wrong.
Thanks once again.

A three phase motor can be started at 'full voltage', but depending on size,
supply considerations and such, often a 'reduced voltage' starting is used.
One 'reduced voltage' method is to have all six leads (two for each phase)
of the motor winding brought out to the controller. If the motor is
designed to work as 480V delta, the starter can temporarily connect the six
leads of the motor as star. So each winding only sees 277V. After the
motor accelerates (as determined by... tach, current level, simple
time-delay or other method), the starter 'breaks' the star at the center and
connects those three leads to an appropriate phase so the motor is now
connected 480V delta. Needless to say, one has to be careful to interlock
the star and delta contactors so they don't pick up at the same time (would
result in short). And the phase connections have to be correct so the motor
doesn't try to reverse direction when switching from star to delta.

Your welcome

daestrom

 

[Louis Bybee]

| A three phase motor can be started at 'full voltage', but depending on size,
| supply considerations and such, often a 'reduced voltage' starting is used.
| One 'reduced voltage' method is to have all six leads (two for each phase)
| of the motor winding brought out to the controller. If the motor is
| designed to work as 480V delta, the starter can temporarily connect the six
| leads of the motor as star. So each winding only sees 277V. After the
| motor accelerates (as determined by... tach, current level, simple
| time-delay or other method), the starter 'breaks' the star at the center and
| connects those three leads to an appropriate phase so the motor is now
| connected 480V delta. Needless to say, one has to be careful to interlock
| the star and delta contactors so they don't pick up at the same time (would
| result in short). And the phase connections have to be correct so the motor
| doesn't try to reverse direction when switching from star to delta.

Wouldn't a 3-pole double-throw contactor be sufficient for that? Since each
winding is going to have one wire connected to a phase line, the other would
go to the contactor, which in one state connects them all to neutral, and in
the other, to the next phase, which will give either a plus 30 or a minus 30
degree phase angle change, depending on which way you go.

While one could "lashup" a home brew Wye-Delta reduced voltage starter, the
consequences of the home brew going South, or the liability issues if one
were to injure property/personnel while doing so, are more than most
reasonable people would risk.

Most commercial Wye Delta starters are interlocked both electrically and
mechanically for obvious reasons, and could also be of the open/closed
transition type.

The links below might be helpful in understanding the theory of Wye Delta
Starters.

http://www.usmotors.com/products/ProFacts/1-120-7.htm

http://www.squared.com/us/products/nema.nsf/bce2f96988bd1a338625643a006e3b29
/32451b329addd9bf85256712005af2f4/$FILE/C_50006-026-01.pdf

I'm sure that Google has many others.

Louis--
*********************************************
Remove the two fish in address to respond

 

[daestrom]

On Sun, 12 Dec 2004 02:46:11 GMT Louis Bybee

| While one could "lashup" a home brew Wye-Delta reduced voltage starter,
the
| consequences of the home brew going South, or the liability issues if
one
| were to injure property/personnel while doing so, are more than most
| reasonable people would risk.
|
| Most commercial Wye Delta starters are interlocked both electrically and
| mechanically for obvious reasons, and could also be of the open/closed
| transition type.

And what kind of interlocking is less likely to result in a shorted
condition than a double throw contactor?

While a large knife switch would work, most often it is done with two,
three-pole single-throw contactors. One contactor shorts the three lines
from the motor together to form a wye, and the other connects each of the
same three lines to the next phase in the rotation. Obviously, if both
contactors are closed at the same time, you have a direct line-line short.
So both electrical and mechanical interlocks are placed between the two
contactors to prevent this.

If you can find a three-pole, double-throw contactor, you could use one.
But remember this thing has to shift while under load (possibly higher than
rated current for the motor if you shift before up to full speed). I'm sure
*somebody* makes such a thing, but the much more common practice I've seen
is to use two single-throw contactors.

daestrom

 

[Bob]

Hi!
When it comes to electrical motor connection wiring what does "all voltage"
term mean? I found it as an alternative wiring for "star-delta" in the motor
controller's manual (no drawings, no explanations).

Thanks!

As an aside to the asides already going on in this thread, I will
venture a guess at the original poster's question.

You mention that something says "Delta-Star" on the starter, as
opposed to "All Voltage". This to me indicates a somewhat poor job of
translating some sort of language into "American-English", so they may
have misinterpreted the commonly used term "Full Voltage" for "All
Voltage" since in some languages, All and Full may be the same word. I
say this because were this being done for England, Autralia or some
other Brittish-English speaking nation, the translation would have
been Direct-On-Line, instead of Full Voltage when referring to
starters.

Am I correct that this is a staerter made in, perhapse, an Asian
nation? If they were as of yet unfamiliar with marketing in the US,
they will make these kinds of mistakes for a while.