Does changing the voltage capability on my TS allow me to work the saw
harder or does it simply help prevent overheating and burnout and a few
breaker runs?

I have already blown out a capacitor on the motor, ugh. (120volt setting)

By doubling the voltage, the current is halved. Therefore the I/R (voltage
drop of the wire, which is a function of the current and resistance in wire)
is cut in half. (more voltage to the saw).
The saw starts better (the most current is on startup) runs better, cooler and
should last longer.
Just my $0.02

Frank

Brandt in western Canada wrote:

Does changing the voltage capability on my TS allow me to work the saw
harder or does it simply help prevent overheating and burnout and a few
breaker runs?

I have already blown out a capacitor on the motor, ugh. (120volt setting)

Be sure that the motor is capable of using 220 volts before changing. Larry
"Brandt in western Canada" wrote in message
...
Does changing the voltage capability on my TS allow me to work the saw
harder or does it simply help prevent overheating and burnout and a few
breaker runs?

I have already blown out a capacitor on the motor, ugh. (120volt setting)

"Brandt in western Canada" wrote in message
...
Does changing the voltage capability on my TS allow me to work the saw
harder or does it simply help prevent overheating and burnout and a few
breaker runs?

I have already blown out a capacitor on the motor, ugh. (120volt setting)

Every answer you get will be academic. The failed capacitor has nothing to
do with what voltage you run. The best reason to run 220 is to be able run
more tools on the feed without having to increase the feeder wire size.

Bob

Why would the saw run cooler if there is more voltage to the saw?

To first order, won't the saw consume the same amount of power when using
120V or 240V (assuming of course the motor is wired correctly for the
appropriate voltage)? That said, in reality I think that saw will consume a
little more power (maybe 5-10% more for a typical installation) in the 240V
configuration than it would in the 120V configuration.

BadgerDog



wrote in message
...
By doubling the voltage, the current is halved. Therefore the I/R (voltage
drop of the wire, which is a function of the current and resistance in
wire)
is cut in half. (more voltage to the saw).
The saw starts better (the most current is on startup) runs better, cooler
and
should last longer.
Just my $0.02

Frank

Brandt in western Canada wrote:

Does changing the voltage capability on my TS allow me to work the saw
harder or does it simply help prevent overheating and burnout and a few
breaker runs?

I have already blown out a capacitor on the motor, ugh. (120volt
setting)

The actual motor wire carries the same current on either voltage. You are
changing from parallel to series connection of the windings.
The drop mentioned is in the feed wire. If it were very large wire, the saw
wouldn't know the difference, but when more current is drawn and the saw
starts to bog down, then the current goes up even more and things snowball.
By keeping the voltage up by drawing less current on 220 and having less
sag, you allow the motor to do its thing and produce rated power at rated
current.

At lower voltage (sag) and higher current, heating rises in the motor
because of IR drop in the windings. This is true at either voltage, but
starts at higher loads because of less drop in the feed.

Wilson
wrote in message
...
By doubling the voltage, the current is halved. Therefore the I/R (voltage
drop of the wire, which is a function of the current and resistance in
wire)
is cut in half. (more voltage to the saw).
The saw starts better (the most current is on startup) runs better, cooler
and
should last longer.
Just my $0.02

Frank

Brandt in western Canada wrote:

Does changing the voltage capability on my TS allow me to work the saw
harder or does it simply help prevent overheating and burnout and a few
breaker runs?

I have already blown out a capacitor on the motor, ugh. (120volt
setting)

"BadgerDog" wrote in message

To first order, won't the saw consume the same amount of power when using
120V or 240V (assuming of course the motor is wired correctly for the
appropriate voltage)?

Yes.

That said, in reality I think that saw will consume a
little more power (maybe 5-10% more for a typical installation) in the
240V
configuration than it would in the 120V configuration.

How do you figure that? It is not logical.

In article ,
BadgerDog wrote:
Why would the saw run cooler if there is more voltage to the saw?

Wilson gave a good answer to this.

To first order, won't the saw consume the same amount of power when using
120V or 240V (assuming of course the motor is wired correctly for the
appropriate voltage)?

Yes - and also assuming that the specified voltage really reaches the
motor, i.e. that there is no "sag" due to I^2R drop in the circuit.

That said, in reality I think that saw will consume a
little more power (maybe 5-10% more for a typical installation) in the 240V
configuration than it would in the 120V configuration.

What is the basis for this? Versus the reality that the voltage "sag"
will always be more for the 120V setup (assuming the same wire in the
circuit) and so the motor windings will draw more current leading to
more heating and so more power consumption.
--
--henry schaffer
hes _AT_ ncsu _DOT_ edu

In article , "BadgerDog" wrote:
Why would the saw run cooler if there is more voltage to the saw?

Because the current is less, and it's current that generates heat, not
voltage.

To first order, won't the saw consume the same amount of power when using
120V or 240V (assuming of course the motor is wired correctly for the
appropriate voltage)?

To a first order approximation, yes.

That said, in reality I think that saw will consume a
little more power (maybe 5-10% more for a typical installation) in the 240V
configuration than it would in the 120V configuration.

Why would you think that?

--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)

Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
by sending email to autoresponder at filterinfo-at-milmac-dot-com
You must use your REAL email address to get a response.

Doug Miller asks:


That said, in reality I think that saw will consume a
little more power (maybe 5-10% more for a typical installation) in the 240V
configuration than it would in the 120V configuration.

Why would you think that?

Baffling. But I know people who swear that switching to 220 doubles a motor's
power, too.

Charlie Self
"The test and the use of man's education is that he finds pleasure in the
exercise of his mind." Jacques Barzun

The power is the same I (current) x E (voltage)
110V x 20 amps = 2200 watts
220V x 10 amps = 2200 watts. Period!
There are other loss that come into play (power factor) but lets leave that stuff
alone!
Also, You are "using" the same current in the motor (at 110 Vs 220) but since the
voltage drop doing to the motor increases (less voltage at the motor), it draws
more current to make up for the power loss (2200 watts)! So it works harder and
the power lines get hotter (that where the loss is going.)

Frank

Charlie Self wrote:

Doug Miller asks:


That said, in reality I think that saw will consume a
little more power (maybe 5-10% more for a typical installation) in the 240V
configuration than it would in the 120V configuration.

Why would you think that?

Baffling. But I know people who swear that switching to 220 doubles a motor's
power, too.

Charlie Self
"The test and the use of man's education is that he finds pleasure in the
exercise of his mind." Jacques Barzun

In article ,
Doug Miller wrote:
In article , "BadgerDog"
wrote:
Why would the saw run cooler if there is more voltage to the saw?

Because the current is less, and it's current that generates heat, not
voltage.

Oh, really?

Which generates more heat:
1) a 60-watt lightbulb (designed for 120V) running at 120v
2) a 60-watt lightbulb (designed for 240V) running at 240v

Note that #1 is drawing 1/2 amp, and #2 is drawing only 1/4 amp.


"Watts is watts", applies -- It doesn't matter how they're produced.

wrote in message
...
The power is the same I (current) x E (voltage)
110V x 20 amps = 2200 watts
220V x 10 amps = 2200 watts. Period!
There are other loss that come into play (power factor) but lets
leave that stuff
alone!
Also, You are "using" the same current in the motor (at 110 Vs 220)
but since the
voltage drop doing to the motor increases (less voltage at the
motor), it draws
more current to make up for the power loss (2200 watts)! So it works
harder and
the power lines get hotter (that where the loss is going.)

Frank


This is almost correct, but your wording has me confused about what
exactly you meant to say.

At 120V, when the current is approximately 2x, the voltage drop is
greater in the feeder cable, so there's less voltage across the motor.
That equates to less current per winding (they're in series here).

At 240V, since the current is roughly half, there's less voltage drop
in the feeder, so more voltage is allowed across the motor, which will
slightly increase the current per winding (which are now paralleled).

Of course, these variables all change with each incremental bit of
developed power. So it's kinda moot.

And (to mention what others have alluded), it gets more detailed when
you start considering the counter-EMF, mutual inductance, load rate of
change, and power factor.

If you have the means to use 240V, just do it. It's advantageous.

Hope this helps.
John Sellers

Robert Bonomi wrote:

In article ,
Doug Miller wrote:
In article , "BadgerDog"
wrote:
Why would the saw run cooler if there is more voltage to the saw?

Because the current is less, and it's current that generates heat, not
voltage.

Oh, really?

Which generates more heat:
1) a 60-watt lightbulb (designed for 120V) running at 120v
2) a 60-watt lightbulb (designed for 240V) running at 240v

Note that #1 is drawing 1/2 amp, and #2 is drawing only 1/4 amp.

"Watts is watts", applies -- It doesn't matter how they're produced.

I agree that "Watts is watts" but wouldn't the temperature of the
conductor(s) come into play since the resistance of a wire increases as the
temperature rises?

--
Jack Novak
Buffalo, NY - USA
(Remove "SPAM" from email address to reply)

In article ,
BadgerDog wrote:
Why would the saw run cooler if there is more voltage to the saw?

To first order, won't the saw consume the same amount of power when using
120V or 240V (assuming of course the motor is wired correctly for the
appropriate voltage)?

For a first order approximation, under 'steady-state' conditions, you
_are_ basically correct. Needless to say, considering only 'steady-state'
conditions is not really meaningful for analysing a table-saw.

The differences occur due to a variety of 'lesser' factors, including:
1) parasitic losses that are not directly related to applied voltage,
2) "stiffness" of the power _source_.
3) speed of response to varying load conditions -- when a motor is trying
to play 'catch up' to an increased load, it draws more power than it
does handling that same load at steady-state. The longer it takes to
get back to steady-state, the more 'excess' power consumed.
4) 'non-resistive' (e.g. 'capacitive', and/or 'inductive') components of
the load. (capacitance, inductance, and resistance react in _different_
ways, in parallel vs series circuits -- different from _each_other_, I
mean. e.g. in series, resistance 'adds', but capacitance 'divides')
5) 'power factor' -- pretty much equivalent to #3

That said, in reality I think that saw will consume a
little more power (maybe 5-10% more for a typical installation) in the 240V
configuration than it would in the 120V configuration.

More commonly, it is the other way around, a device is slightly _more_
efficient at the higher voltage. On a _good_ day, it may approach 2%.

However, there are no 'guarantees'. It depends, _entirely_, on the design of
the specific device.


BadgerDog



wrote in message
...
By doubling the voltage, the current is halved. Therefore the I/R (voltage
drop of the wire, which is a function of the current and resistance in
wire)
is cut in half. (more voltage to the saw).
The saw starts better (the most current is on startup) runs better, cooler
and
should last longer.
Just my $0.02

Frank

Brandt in western Canada wrote:

Does changing the voltage capability on my TS allow me to work the saw
harder or does it simply help prevent overheating and burnout and a few
breaker runs?

I have already blown out a capacitor on the motor, ugh. (120volt
setting)

John, series on 240, parallel on 120.
When you have sag and current goes up, it's up in the feed as well as in the
motor, so you actually do consume more power from the box, and a little more
in the motor (the IR heating).

Wilson
"John Sellers" wrote in message
. ..

wrote in message
...
The power is the same I (current) x E (voltage)
110V x 20 amps = 2200 watts
220V x 10 amps = 2200 watts. Period!
There are other loss that come into play (power factor) but lets
leave that stuff
alone!
Also, You are "using" the same current in the motor (at 110 Vs 220)
but since the
voltage drop doing to the motor increases (less voltage at the
motor), it draws
more current to make up for the power loss (2200 watts)! So it works
harder and
the power lines get hotter (that where the loss is going.)

Frank


This is almost correct, but your wording has me confused about what
exactly you meant to say.

At 120V, when the current is approximately 2x, the voltage drop is
greater in the feeder cable, so there's less voltage across the motor.
That equates to less current per winding (they're in series here).

At 240V, since the current is roughly half, there's less voltage drop
in the feeder, so more voltage is allowed across the motor, which will
slightly increase the current per winding (which are now paralleled).

Of course, these variables all change with each incremental bit of
developed power. So it's kinda moot.

And (to mention what others have alluded), it gets more detailed when
you start considering the counter-EMF, mutual inductance, load rate of
change, and power factor.

If you have the means to use 240V, just do it. It's advantageous.

Hope this helps.
John Sellers

In article t,
Bob Davis wrote:

"Brandt in western Canada" wrote in message
...
Does changing the voltage capability on my TS allow me to work the saw
harder or does it simply help prevent overheating and burnout and a few
breaker runs?

I have already blown out a capacitor on the motor, ugh. (120volt setting)

Every answer you get will be academic.

Including yours? evil grin

The failed capacitor has nothing to
do with what voltage you run. The best reason to run 220 is to be able run
more tools on the feed without having to increase the feeder wire size.

Bob

Consume more power? The first guy to respond to the question was spot
on. Has everybody who attemps to reply actually run a bunch of tool on
both 120 and 240? Same tools? Tried both ways? If you use a gawdawful
heavy cord direct from the service panel, maybe you couldn't tell the
diffence. In the real world, with similar gauge wiring, you'll find the
saw will start quicker and bog less. Since it bogs less, it runs
cooler. IMHO

rhg

BadgerDog wrote:

Why would the saw run cooler if there is more voltage to the saw?

To first order, won't the saw consume the same amount of power when using
120V or 240V (assuming of course the motor is wired correctly for the
appropriate voltage)? That said, in reality I think that saw will consume a
little more power (maybe 5-10% more for a typical installation) in the 240V
configuration than it would in the 120V configuration.

BadgerDog



wrote in message
...

By doubling the voltage, the current is halved. Therefore the I/R (voltage
drop of the wire, which is a function of the current and resistance in

wire)

is cut in half. (more voltage to the saw).
The saw starts better (the most current is on startup) runs better, cooler

and

should last longer.
Just my $0.02

Frank

Brandt in western Canada wrote:


Does changing the voltage capability on my TS allow me to work the saw
harder or does it simply help prevent overheating and burnout and a few
breaker runs?

I have already blown out a capacitor on the motor, ugh. (120volt

setting)

Robert Galloway wrote:

Consume more power? The first guy to respond to the question was spot
on. Has everybody who attemps to reply actually run a bunch of tool on
both 120 and 240? Same tools? Tried both ways? If you use a gawdawful
heavy cord direct from the service panel, maybe you couldn't tell the
diffence. In the real world, with similar gauge wiring, you'll find the
saw will start quicker and bog less. Since it bogs less, it runs
cooler. IMHO

In the real world if you're using the same gage wiring for a 240 volt
circuit and a 120 volt circuit that has to carry twice the current then
it's time to sue the electrician.

rhg

BadgerDog wrote:

Why would the saw run cooler if there is more voltage to the saw?

To first order, won't the saw consume the same amount of power when using
120V or 240V (assuming of course the motor is wired correctly for the
appropriate voltage)? That said, in reality I think that saw will
consume a little more power (maybe 5-10% more for a typical installation)
in the 240V configuration than it would in the 120V configuration.

BadgerDog



wrote in message
...

By doubling the voltage, the current is halved. Therefore the I/R
(voltage drop of the wire, which is a function of the current and
resistance in

wire)

is cut in half. (more voltage to the saw).
The saw starts better (the most current is on startup) runs better,
cooler

and

should last longer.
Just my $0.02

Frank

Brandt in western Canada wrote:


Does changing the voltage capability on my TS allow me to work the saw
harder or does it simply help prevent overheating and burnout and a few
breaker runs?

I have already blown out a capacitor on the motor, ugh. (120volt

setting)




--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)

In article ,
Nova wrote:
Robert Bonomi wrote:

In article ,
Doug Miller wrote:
In article , "BadgerDog"
wrote:
Why would the saw run cooler if there is more voltage to the saw?

Because the current is less, and it's current that generates heat, not
voltage.

Oh, really?

Which generates more heat:
1) a 60-watt lightbulb (designed for 120V) running at 120v
2) a 60-watt lightbulb (designed for 240V) running at 240v

Note that #1 is drawing 1/2 amp, and #2 is drawing only 1/4 amp.

"Watts is watts", applies -- It doesn't matter how they're produced.

I agree that "Watts is watts" but wouldn't the temperature of the
conductor(s) come into play since the resistance of a wire increases as the
temperature rises?

"Could be... Could be", says he. grin

The light-bulb design already takes that temperature rise into consideration.
The filament is designed to have the 'proper' resistance _at_operating_temp_.

Which is why incandescent bulbs _almost_ _always_ fail when they are turned
on. The initial, or 'inrush' current is _many_, *MANY*, times higher than
the 'operating current'. The 'cold' resistance of a 100 watt light-bulb is
typically in the _low_ single digits.

As a point of engineering detail, the operating temperature of both bulbs
will be fairly close to the same value. Incandescent bulbs of the same
wattage are _amazingly_ close to each other in the 'color' of the light
generated. which is _directly_ related to the temperature of the filament.
A white light 'color temperature' difference of as little as 100 degrees C is
easily detected by someone who is looking for it. Typical halogen white light
color temperatures are around 4500 degrees. The 'white' on a color CRT
is frequently in the mid 6000's. True daylight, if i recall correctly, is
around 9500 degrees. Tungsten-filament incandescent, poor things, are
down around 3000 degrees.


*IF* the filament in both bulbs is made of the same material, the 240v bulb
has a filament that is longer and thinner than the 120V one.

Frequently, however, the higher voltage bulbs are made with a somewhat
_different_ (higher resistance) composition of material for the filament.
Allowing the filament construction to be thicker than the 120V 'counterpart'.
This improves the mechanical stability, and the ability to withstand shock
and/or vibration.

120 volt light circuit maybe 14-3/G Most of us have shop circuits wired
with 12-3/G and an occasional 10-3/G. 12-3/G goes most places in my
shop 120 or 240.

rhg

J. Clarke wrote:
Robert Galloway wrote:


Consume more power? The first guy to respond to the question was spot
on. Has everybody who attemps to reply actually run a bunch of tool on
both 120 and 240? Same tools? Tried both ways? If you use a gawdawful
heavy cord direct from the service panel, maybe you couldn't tell the
diffence. In the real world, with similar gauge wiring, you'll find the
saw will start quicker and bog less. Since it bogs less, it runs
cooler. IMHO


In the real world if you're using the same gage wiring for a 240 volt
circuit and a 120 volt circuit that has to carry twice the current then
it's time to sue the electrician.


rhg

BadgerDog wrote:


Why would the saw run cooler if there is more voltage to the saw?

To first order, won't the saw consume the same amount of power when using
120V or 240V (assuming of course the motor is wired correctly for the
appropriate voltage)? That said, in reality I think that saw will
consume a little more power (maybe 5-10% more for a typical installation)
in the 240V configuration than it would in the 120V configuration.

BadgerDog



wrote in message
...


By doubling the voltage, the current is halved. Therefore the I/R
(voltage drop of the wire, which is a function of the current and
resistance in

wire)


is cut in half. (more voltage to the saw).
The saw starts better (the most current is on startup) runs better,
cooler

and


should last longer.
Just my $0.02

Frank

Brandt in western Canada wrote:



Does changing the voltage capability on my TS allow me to work the saw
harder or does it simply help prevent overheating and burnout and a few
breaker runs?

I have already blown out a capacitor on the motor, ugh. (120volt

setting)

As I understand it, your single pole (120v) 20 amp breaker trips under
a heavy load, more than 2400watts. By rewiring to 220 (or 240) volt,
you install a 2-pole breaker, probably 20amps PER leg. That kinda
makes you supply equivalent to 40 amps (~4800 watts) . Supplying the
saw with as much as double the current, certianly would make the
breaker trip less.

loadOn Sun, 13 Jun 2004 11:49:07 -0600, in rec.woodworking you wrote:

On Sun, 13 Jun 2004 00:36:05 GMT, Brandt in western Canada
wrote:

I have a 1 HP-110V Crapsman TS, whenever I saw hardwood lumbers the circuit
breaker trips. I also encountered the tripping problems with my 1-1/2HP-110V
compressor whenever the compressor loading. I rewired both machines to 220V and
the problems gone forever.

I learn these tips from helpful posters here. By rewiring it to 220V you really
have nothing to lose.

Does changing the voltage capability on my TS allow me to work the saw
harder or does it simply help prevent overheating and burnout and a few
breaker runs?

I have already blown out a capacitor on the motor, ugh. (120volt setting)

Robert Galloway wrote:

120 volt light circuit maybe 14-3/G Most of us have shop circuits wired
with 12-3/G and an occasional 10-3/G. 12-3/G goes most places in my
shop 120 or 240.

You're supposed to size the wire for the current and the length of the run
so that the voltage drop at max load is allowable. If you do that then saw
should not be "bogging" due to voltage drop in the wiring under heavy load.


rhg

J. Clarke wrote:
Robert Galloway wrote:


Consume more power? The first guy to respond to the question was spot
on. Has everybody who attemps to reply actually run a bunch of tool on
both 120 and 240? Same tools? Tried both ways? If you use a gawdawful
heavy cord direct from the service panel, maybe you couldn't tell the
diffence. In the real world, with similar gauge wiring, you'll find the
saw will start quicker and bog less. Since it bogs less, it runs
cooler. IMHO


In the real world if you're using the same gage wiring for a 240 volt
circuit and a 120 volt circuit that has to carry twice the current then
it's time to sue the electrician.


rhg

BadgerDog wrote:


Why would the saw run cooler if there is more voltage to the saw?

To first order, won't the saw consume the same amount of power when
using 120V or 240V (assuming of course the motor is wired correctly for
the
appropriate voltage)? That said, in reality I think that saw will
consume a little more power (maybe 5-10% more for a typical
installation) in the 240V configuration than it would in the 120V
configuration.

BadgerDog



wrote in message
...


By doubling the voltage, the current is halved. Therefore the I/R
(voltage drop of the wire, which is a function of the current and
resistance in

wire)


is cut in half. (more voltage to the saw).
The saw starts better (the most current is on startup) runs better,
cooler

and


should last longer.
Just my $0.02

Frank

Brandt in western Canada wrote:



Does changing the voltage capability on my TS allow me to work the saw
harder or does it simply help prevent overheating and burnout and a
few breaker runs?

I have already blown out a capacitor on the motor, ugh. (120volt

setting)






--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)

In article s.com,
(Robert Bonomi) wrote:

Keep in mind that the light bulb example is totally different than the
saw. In the light bulb, the watts go into heating the filament. A 60
watt bulb is just that regardless of the voltage/current relationship to
create the power.

In the case of the saw, most of the energy goes into cutting wood. Only
a small amount goes into heating the motor. The motor heating goes as
I^2*R. As the lower voltage requires a higher current, there is more
heating in the lower voltage situation.

Dick

In article ,
Doug Miller wrote:
In article , "BadgerDog"
wrote:
Why would the saw run cooler if there is more voltage to the saw?

Because the current is less, and it's current that generates heat, not
voltage.

Oh, really?

Which generates more heat:
1) a 60-watt lightbulb (designed for 120V) running at 120v
2) a 60-watt lightbulb (designed for 240V) running at 240v

Note that #1 is drawing 1/2 amp, and #2 is drawing only 1/4 amp.


"Watts is watts", applies -- It doesn't matter how they're produced.

In article s.com,
(Robert Bonomi) wrote:

All incandescent lamps use tungsten filaments. There are some trace
elements added that tend to prolong life but that material is not
altered for different voltages.

Halogen lampsd have one of the halogen gasses in the envelope. This
creates a "halogen cycle" where the evaporated tungsten combines with a
halogen gas molecule and then breaks down when the combined molecule
strikes the filament again. Thus the lamp can operate at a higher
temperature before failure.

Dick


Frequently, however, the higher voltage bulbs are made with a somewhat
_different_ (higher resistance) composition of material for the filament.

Allowing the filament construction to be thicker than the 120V
'counterpart'.
This improves the mechanical stability, and the ability to withstand
shock
and/or vibration.

"Edwin Pawlowski" wrote in message
...

"BadgerDog" wrote in message

To first order, won't the saw consume the same amount of power when
using
120V or 240V (assuming of course the motor is wired correctly for the
appropriate voltage)?

Yes.

That said, in reality I think that saw will consume a
little more power (maybe 5-10% more for a typical installation) in the
240V
configuration than it would in the 120V configuration.

How do you figure that? It is not logical.



Here's my rational for proposing that the 240V configuration gives the motor
slightly more power.

First consider the 120V configuration:
Lets suppose that the motor draws 16A from the 120V source. The motor
windings will be connected in parallel, so for two windings in parallel,
each winding will have 8A flowing through it and each will have close to
120V accross it (it is a little less than 120V because of the voltage drop
in the wiring). If the wiring has a resistance of 0.3 ohms (not
unreasonable for a run of 12 AWG wire), the voltage drop due to the wiring
would be 0.3 ohm * 16 A = 4.8 V. So, the each motor winding would see 120V -
4.8 V = 115.2V. Note, at this point we can calculate the resistance due to
the motor windings: 115.2 V / 8 A = 14.4 ohm. To double check the
calculations: For a single winding of 14.4 ohm, the resistance of two
winding in parallel will be 1/2 that of one (i.e. 7.2 ohm). The 120 V
circuit "sees" a total resistance of 0.3 ohm + 7.2 ohm = 7.5 ohm; 120 V /
7.5 ohm = 16A (as we originally supposed). In terms of power, the wiring
will use 16A * 4.8V = 76.8 Watts. The motor will use 16A * 115.2 V = 1843.2
Watts. Total power is 76.8 W + 1843.2 W = 1920 W, in agrrement with 16 A *
120 V = 1920 W for the total circuit.

Now consider the same motor configured for 240V operation:
Now the two winding are in series with each other and the wiring, so
doubling the voltage does not exactly halve the current (since the total
circuit resistance changes). The total circuit resistance will be 0.3 ohm
(assuming same run of wiring is used) + 28.8 ohm (two 14.4 ohm windings in
series) = 29.1 ohm. The current will be 240 V / 29.1 ohm = 8.25 A. Now we
can calculate the voltage drops: for the wiring we have 0.3 ohm * 8.25 A =
2.48V (close to 1/2 the 4.8 V drop for the 120 V configuration); 14.4 ohm *
8.25 A = 118.8 V for EACH winding. The winding together in series give a
drop of 2 * 118.8 V = 237.6 V; total circuit voltage drop of 2.475V + 237.6V
= 240.075V (slightly off from 240V due to rounding of current to 8.25A).
So, in the 240 V configuration, each winding sees a little more voltage AND
a little more current, so therefore the motor gets a little more power. We
can also calculate the power involved: the wiring uses 8.25A * 2.475 V =
20.4 W and the motor will use 8.25 A * 237.6 V = 1960.2 W, for a combine
total of 20.4 W + 1960.2 W = 1980.6 W.


To summarize:
120 V configuration: 1920 Watts total, 76.8 Watts for the wiring and 1843.2
Watts for the motor
240 V configuration: 1980.6 Watts total, 20.4 W for the wiring and 1960.2
Watts for the motor

Compared to the 120V configuration, when wired for 240 V the motor gets
1960.2 W - 1843.2 W = 117 W more power, or a (117/1843.2)*100 = 6.3%
increase.

Granted, I've simplified the analysis by only considering the resistive
loads (i.e. I've implicitly assumed that the reactance due to the motor's
inductance has been balances out by the reactance of the capacitor). Also,
I realize that motors are more complicated than I have described them; for
example the amount of current they draw depends on the level of mechnical
resistance they are working against (e.g. freely spinning saw blade versus
cutting 2 inch thick maple). However, I hope I've shed some light on the an
aspect of the 120V versus 240V debate in order to show that it is not as
simple as "double the voltage, halve the current" response that is given so
often.

Disclaimer: I am not an electrician, but I do have a background with some
things electrical.

BadgerDog

In article s.com,
says...
In article ,
Doug Miller wrote:
In article , "BadgerDog"
wrote:
Why would the saw run cooler if there is more voltage to the saw?

Because the current is less, and it's current that generates heat, not
voltage.

Oh, really?

Which generates more heat:
1) a 60-watt lightbulb (designed for 120V) running at 120v
2) a 60-watt lightbulb (designed for 240V) running at 240v

Note that #1 is drawing 1/2 amp, and #2 is drawing only 1/4 amp.

"Watts is watts", applies -- It doesn't matter how they're produced.

Point taken; just the same, a dual-voltage motor *does* run cooler at
240V than it does at 120V.

Whoops, got the motor connections backwards. And that was after I
checked and swapped them - twice.

I agree about the increased power draw when the motor load increases;
and so do the parasitic losses. But, that's why I said it's really a
moot issue. There's no such thing as constant load with a woodworking
machine. So, it doesn't make much sense to debate the issue of small
current changes. Bottom line - 240V makes for easier use of the
power, with less wasted energy.

Sorry for the confusion.
John Sellers

"Wilson" wrote in message thlink.net...
John, series on 240, parallel on 120.
When you have sag and current goes up, it's up in the feed as well as in the
motor, so you actually do consume more power from the box, and a little more
in the motor (the IR heating).

Wilson
"John Sellers" wrote in message
. ..

Robert Bonomi wrote:

I agree that "Watts is watts" but wouldn't the temperature of the
conductor(s) come into play since the resistance of a wire increases as the
temperature rises?

"Could be... Could be", says he. grin

The light-bulb design already takes that temperature rise into consideration.
The filament is designed to have the 'proper' resistance _at_operating_temp_.

I wasn't referring to the resistance of the filament but rather the conductors
feeding a motor being operated at 110V verses 220V. The amperage being double
when the equipment is operated at 110V would cause the conductors to generate more
heat decreasing the overall efficiency. Granted, with a short run the difference
would be minimal.

--
Jack Novak
Buffalo, NY - USA
(Remove "SPAM" from email address to reply)

Correct. As I mentioned in a different post, in an ideal world, every
application of a power tool would have copper coming to it of such size
that the maximum load of the tool wouldn't produce a discernible voltage
drop. This would include the cord provided by the manufacturer of the
tool. In the real world, I've been happier with tools running on 220.
I've spend a lot of time with most of them both ways. You pay's your
money and takes your choice. My advice is, if the tool stays in one
place all the time and 220 is handy, use it. YMMV.

rhg

J. Clarke wrote:

Robert Galloway wrote:


120 volt light circuit maybe 14-3/G Most of us have shop circuits wired
with 12-3/G and an occasional 10-3/G. 12-3/G goes most places in my
shop 120 or 240.


You're supposed to size the wire for the current and the length of the run
so that the voltage drop at max load is allowable. If you do that then saw
should not be "bogging" due to voltage drop in the wiring under heavy load.


rhg

J. Clarke wrote:

Robert Galloway wrote:



Consume more power? The first guy to respond to the question was spot
on. Has everybody who attemps to reply actually run a bunch of tool on
both 120 and 240? Same tools? Tried both ways? If you use a gawdawful
heavy cord direct from the service panel, maybe you couldn't tell the
diffence. In the real world, with similar gauge wiring, you'll find the
saw will start quicker and bog less. Since it bogs less, it runs
cooler. IMHO


In the real world if you're using the same gage wiring for a 240 volt
circuit and a 120 volt circuit that has to carry twice the current then
it's time to sue the electrician.



rhg

BadgerDog wrote:



Why would the saw run cooler if there is more voltage to the saw?

To first order, won't the saw consume the same amount of power when
using 120V or 240V (assuming of course the motor is wired correctly for
the
appropriate voltage)? That said, in reality I think that saw will
consume a little more power (maybe 5-10% more for a typical
installation) in the 240V configuration than it would in the 120V
configuration.

BadgerDog



wrote in message
...



By doubling the voltage, the current is halved. Therefore the I/R
(voltage drop of the wire, which is a function of the current and
resistance in

wire)



is cut in half. (more voltage to the saw).
The saw starts better (the most current is on startup) runs better,
cooler

and



should last longer.
Just my $0.02

Frank

Brandt in western Canada wrote:




Does changing the voltage capability on my TS allow me to work the saw
harder or does it simply help prevent overheating and burnout and a
few breaker runs?

I have already blown out a capacitor on the motor, ugh. (120volt

setting)

This would be true if you didn't rewire the motor from a parallel
connection to a series connection when going from 110 to 220. Current,
therefore I^2R losses, should be the same. Most small motors, however
don't change the connection to the start winding so it DOES carry twice
the current during the brief period it's active.

rhg

Richard Cline wrote:

In article s.com,
(Robert Bonomi) wrote:

Keep in mind that the light bulb example is totally different than the
saw. In the light bulb, the watts go into heating the filament. A 60
watt bulb is just that regardless of the voltage/current relationship to
create the power.

In the case of the saw, most of the energy goes into cutting wood. Only
a small amount goes into heating the motor. The motor heating goes as
I^2*R. As the lower voltage requires a higher current, there is more
heating in the lower voltage situation.

Dick


In article ,
Doug Miller wrote:

In article , "BadgerDog"
wrote:

Why would the saw run cooler if there is more voltage to the saw?

Because the current is less, and it's current that generates heat, not
voltage.

Oh, really?

Which generates more heat:
1) a 60-watt lightbulb (designed for 120V) running at 120v
2) a 60-watt lightbulb (designed for 240V) running at 240v

Note that #1 is drawing 1/2 amp, and #2 is drawing only 1/4 amp.


"Watts is watts", applies -- It doesn't matter how they're produced.

"BadgerDog" wrote in message
To summarize:
120 V configuration: 1920 Watts total, 76.8 Watts for the wiring and
1843.2
Watts for the motor
240 V configuration: 1980.6 Watts total, 20.4 W for the wiring and 1960.2
Watts for the motor

Compared to the 120V configuration, when wired for 240 V the motor gets
1960.2 W - 1843.2 W = 117 W more power, or a (117/1843.2)*100 = 6.3%
increase.

Granted, I've simplified the analysis by only considering the resistive
loads (i.e. I've implicitly assumed that the reactance due to the motor's
inductance has been balances out by the reactance of the capacitor).

Interesting. I'm not sure about the "simplified" part though
Ed

More consumption in the 240 volt mode. Makes sense. Doesn't work out
that way. The rotating motor functions as a generator. Its generated
emf opposes the supplied emf. Its ability to counter the supplied
voltage is what limits the net draw. If there's voltage drop in the
line, (which is more pronounced in the 120v mode) then the motor is
less effective as a generator, less effective at opposing the applied
emf and generates more temp rise. Motors run best at full rated
voltage. However you want to supply this, the result is the same. On
120 volt, use the largest gauge wire. For a given gauge, 240v will do a
better job of keeping your motor spun up to the full rated RPM and
therefore do the best job of generating counter emf.

bob g.

BadgerDog wrote:

Why would the saw run cooler if there is more voltage to the saw?

To first order, won't the saw consume the same amount of power when using
120V or 240V (assuming of course the motor is wired correctly for the
appropriate voltage)? That said, in reality I think that saw will consume a
little more power (maybe 5-10% more for a typical installation) in the 240V
configuration than it would in the 120V configuration.

BadgerDog



wrote in message
...

By doubling the voltage, the current is halved. Therefore the I/R (voltage
drop of the wire, which is a function of the current and resistance in

wire)

is cut in half. (more voltage to the saw).
The saw starts better (the most current is on startup) runs better, cooler

and

should last longer.
Just my $0.02

Frank

Brandt in western Canada wrote:


Does changing the voltage capability on my TS allow me to work the saw
harder or does it simply help prevent overheating and burnout and a few
breaker runs?

I have already blown out a capacitor on the motor, ugh. (120volt

setting)