"John Larkin" wrote in
message ...
Wow. If it was delta, then 110 3-phase would require 6 wires (or five
if you cheat and share one corner) so the 110 3-phase motor would need
three isolated windings and most likely a 6-pole on/off switch. Was it
really like that?

Nope. Draw a picture of a Delta, center-tap each winding, and the three
center taps form another delta at half the voltage. Used a perfectly
standard (for 1922) 3 phase, 3 wire, 110v, 25Hz motor.

The 110 volt service made no connection to the corners of the 220 delta. The
110 delta was fed only from the center taps.

"John Larkin" wrote in
message ...
Wow. If it was delta, then 110 3-phase would require 6 wires (or five
if you cheat and share one corner) so the 110 3-phase motor would need
three isolated windings and most likely a 6-pole on/off switch. Was it
really like that?

Nope. Draw a picture of a Delta, center-tap each winding, and the three
center taps form another delta at half the voltage. Used a perfectly
standard (for 1922) 3 phase, 3 wire, 110v, 25Hz motor.

The 110 volt service made no connection to the corners of the 220 delta. The
110 delta was fed only from the center taps.

On Sat, 3 Jan 2004 14:10:54 -0500, "BFoelsch"
wrote:


"John Larkin" wrote in
message ...
Wow. If it was delta, then 110 3-phase would require 6 wires (or five
if you cheat and share one corner) so the 110 3-phase motor would need
three isolated windings and most likely a 6-pole on/off switch. Was it
really like that?

Nope. Draw a picture of a Delta, center-tap each winding, and the three
center taps form another delta at half the voltage. Used a perfectly
standard (for 1922) 3 phase, 3 wire, 110v, 25Hz motor.


Oh, yeah, OK. New Orleans is mostly below sea level, and the
Mississippi runs along most of it and peaks way above in the spring.
Up to fairly recently, New Orleans was drained by ancient pumps with
ancient switchgear, running on 25 Hz, and all the generators that made
the 25 Hz were (of course) in the city, below sea level too.

John

On Sat, 3 Jan 2004 14:10:54 -0500, "BFoelsch"
wrote:


"John Larkin" wrote in
message ...
Wow. If it was delta, then 110 3-phase would require 6 wires (or five
if you cheat and share one corner) so the 110 3-phase motor would need
three isolated windings and most likely a 6-pole on/off switch. Was it
really like that?

Nope. Draw a picture of a Delta, center-tap each winding, and the three
center taps form another delta at half the voltage. Used a perfectly
standard (for 1922) 3 phase, 3 wire, 110v, 25Hz motor.


Oh, yeah, OK. New Orleans is mostly below sea level, and the
Mississippi runs along most of it and peaks way above in the spring.
Up to fairly recently, New Orleans was drained by ancient pumps with
ancient switchgear, running on 25 Hz, and all the generators that made
the 25 Hz were (of course) in the city, below sea level too.

John

Clever, clever, delta, New Orleans.........................

And who said there's no wit here!

Yeah, 25 Hz has kind of pooped out recently. It is still generated on the
Canadian side of Niagara Falls, but it is all converted to 60.

Across the river in Buffalo, the utility still provides 25 Hz to about 50
customers, but they have announced its termination as of 2007. There are a
few isolated paper mills that make their own, I believe that Con Edison
makes a little, and there is one isolated pocket in Iowa, but that's all I
know of that's left.

I remember when 60, 50 and 25 cycle motors were all stocked items!

Thanks in advance.

"John Larkin" wrote in
message ...
On Sat, 3 Jan 2004 14:10:54 -0500, "BFoelsch"
wrote:


"John Larkin" wrote in
message ...
Wow. If it was delta, then 110 3-phase would require 6 wires (or five
if you cheat and share one corner) so the 110 3-phase motor would need
three isolated windings and most likely a 6-pole on/off switch. Was it
really like that?

Nope. Draw a picture of a Delta, center-tap each winding, and the three
center taps form another delta at half the voltage. Used a perfectly
standard (for 1922) 3 phase, 3 wire, 110v, 25Hz motor.


Oh, yeah, OK. New Orleans is mostly below sea level, and the
Mississippi runs along most of it and peaks way above in the spring.
Up to fairly recently, New Orleans was drained by ancient pumps with
ancient switchgear, running on 25 Hz, and all the generators that made
the 25 Hz were (of course) in the city, below sea level too.

John

Clever, clever, delta, New Orleans.........................

And who said there's no wit here!

Yeah, 25 Hz has kind of pooped out recently. It is still generated on the
Canadian side of Niagara Falls, but it is all converted to 60.

Across the river in Buffalo, the utility still provides 25 Hz to about 50
customers, but they have announced its termination as of 2007. There are a
few isolated paper mills that make their own, I believe that Con Edison
makes a little, and there is one isolated pocket in Iowa, but that's all I
know of that's left.

I remember when 60, 50 and 25 cycle motors were all stocked items!

Thanks in advance.

"John Larkin" wrote in
message ...
On Sat, 3 Jan 2004 14:10:54 -0500, "BFoelsch"
wrote:


"John Larkin" wrote in
message ...
Wow. If it was delta, then 110 3-phase would require 6 wires (or five
if you cheat and share one corner) so the 110 3-phase motor would need
three isolated windings and most likely a 6-pole on/off switch. Was it
really like that?

Nope. Draw a picture of a Delta, center-tap each winding, and the three
center taps form another delta at half the voltage. Used a perfectly
standard (for 1922) 3 phase, 3 wire, 110v, 25Hz motor.


Oh, yeah, OK. New Orleans is mostly below sea level, and the
Mississippi runs along most of it and peaks way above in the spring.
Up to fairly recently, New Orleans was drained by ancient pumps with
ancient switchgear, running on 25 Hz, and all the generators that made
the 25 Hz were (of course) in the city, below sea level too.

John

I read in sci.electronics.design that John Larkin jjlarkin@highlandSNIP
techTHISnologyPLEASE.com wrote (in ke7evvo4mvalsj6km5ja2u4di666ge0g49@
4ax.com) about 'why 3-phase power?', on Sat, 3 Jan 2004:

Up to fairly recently, New Orleans was drained by ancient pumps with
ancient switchgear, running on 25 Hz, and all the generators that made
the 25 Hz were (of course) in the city, below sea level too.

Naturally: 25 Hz is an unusually LOW frequency.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

I read in sci.electronics.design that John Larkin jjlarkin@highlandSNIP
techTHISnologyPLEASE.com wrote (in ke7evvo4mvalsj6km5ja2u4di666ge0g49@
4ax.com) about 'why 3-phase power?', on Sat, 3 Jan 2004:

Up to fairly recently, New Orleans was drained by ancient pumps with
ancient switchgear, running on 25 Hz, and all the generators that made
the 25 Hz were (of course) in the city, below sea level too.

Naturally: 25 Hz is an unusually LOW frequency.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

Rob Paisley wrote:
Bill wrote in message ...

wrote:


In sci.electronics.basics Rob Paisley wrote:

| For larger horsepower motors, Three Phases means that they will
| start with no external mechanical assistance.

And, as I understand it, they can then "stand on one leg" although they
will be a bit "shaky".


You can also reverse the rotation by swapping two of the phases. If one
phase is blown you can start it by giving it a spin in the right
direction, 'without' getting your hand caught

Bill Baka


I am not sure if a 3 phase motor would even rotate unloaded on 2
phases but it certainly would not develop a usable amount of
horsepower. I would suspect that running on 1 phase would be out of
the question.

I do know that if a loaded 3 phase motor blows a fuse it will almost
always blow a fuse in one of the other lines due to an overload. Due
to the way the control power for the motor is connected the starter
will then open the circuit if it did not already do so when the first
fuse failed.

Also, there is a number of 1.57 being bandied about in this thread
for the relative horse power of a 3 phase versus single motor for a
given current. This number should be 1.73 (The square root of 3.

Rob.
The motor I replaced was on an air conditioning blower and would rotate
if given a boost before turning on the power, but as you said not with
enough power. It just would not start without the third phase. The fix
was to replace a 3/4 horse motor with a 1 horse motor in the same NEMA
frame size. It was a 480 volt unit so we did not play much with it and
just tossed it. Seems us engineer types prefer 5 volt stuff.
Bill Baka

Rob Paisley wrote:
Bill wrote in message ...

wrote:


In sci.electronics.basics Rob Paisley wrote:

| For larger horsepower motors, Three Phases means that they will
| start with no external mechanical assistance.

And, as I understand it, they can then "stand on one leg" although they
will be a bit "shaky".


You can also reverse the rotation by swapping two of the phases. If one
phase is blown you can start it by giving it a spin in the right
direction, 'without' getting your hand caught

Bill Baka


I am not sure if a 3 phase motor would even rotate unloaded on 2
phases but it certainly would not develop a usable amount of
horsepower. I would suspect that running on 1 phase would be out of
the question.

I do know that if a loaded 3 phase motor blows a fuse it will almost
always blow a fuse in one of the other lines due to an overload. Due
to the way the control power for the motor is connected the starter
will then open the circuit if it did not already do so when the first
fuse failed.

Also, there is a number of 1.57 being bandied about in this thread
for the relative horse power of a 3 phase versus single motor for a
given current. This number should be 1.73 (The square root of 3.

Rob.
The motor I replaced was on an air conditioning blower and would rotate
if given a boost before turning on the power, but as you said not with
enough power. It just would not start without the third phase. The fix
was to replace a 3/4 horse motor with a 1 horse motor in the same NEMA
frame size. It was a 480 volt unit so we did not play much with it and
just tossed it. Seems us engineer types prefer 5 volt stuff.
Bill Baka