# 280V motor on 230V circuit

Discussion in 'Electronic Repair' started by Deodiaus, Apr 26, 2008.

1. ### Don KellyGuest

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Fair enough- but still overkill. For the bulk of the calculations that one
does, single precision is more than adequate. Anything more, even for
comparison of numbers is really fluff.
I simply set my display to show the desired sig figs and let the calculator
deal with the rest in its normal internal mode. I don't want to see the
extra digits, or , if I do, 1 or 2 is sufficient. Ditto with the computer.
Only if I am dealing with ill conditioned sets of simultaneous equations ,
will I really require double precision.

2. ### bzGuest

pounds (mass), lbm, as opposed to pounds (force), lbf, or lb.

It is necessary to distinguish between mass and force but they are both
measured in pounds in the english system.

Metric is 'much simpler' with grams(mass) and newtons(force).

--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

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3. ### krwGuest

The "English" system uses the "stone" as the measurement of mass.
The pound ('lb') is the unit of *FORCE*.
Evidently *you* think the "English" system is too complicated. ;-)

4. ### bzGuest

http://www.engineeringtoolbox.com/mass-weight-d_589.html

I don't think any of them are 'too complicated'.
It is easy enough to convert from one to another.

However, FAILURE to convert has been known to cause problems, such as a
Mars mission that crashed because the wrong units were used.

http://www.cnn.com/TECH/space/9909/30/mars.metric/

--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

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5. ### charlesGuest

The 'Stone' is a unit of mass, not "The unit of mass"

All the engineering I ever learned in the British (Imperial) system used
pounds.

No - the modern Metric system uses the kilogramme as its fundamental unit.

6. ### krwGuest

It is *the* unit of mass. The pound-mass is a recent abortion.
You must be a kid.
Only if you spell funny.

7. ### charlesGuest

cleverly, we use the same word for two different things to confuse
foreigners.

8. ### charlesGuest

No - 68!!!
Even in 1961 the MKS system was the norm.

9. ### bzGuest

Really gets to be fun when working with things like foot-pounds,
as in torque, angular momentum, and the pressure due to a certain depth of
water.

Trying to remember when the pounds are mass and when they are force gets
to be fun.

--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

10. ### krwGuest

I first heard pound-mass about ten years ago. All through high
school and college the English unit for mass was the stone (as in
the FSF system of measurements).
Sure, but you still spell like a frog. ;-)

11. ### Don KellyGuest

In the early '50's there were two other units around- the poundal (1/g
pounds force) or a mass called a slug (g pounds mass). Learning mechanics
with these units (don't use them together)is worse than working in the
stone, furlong, fortnight set of units.
The poundal was introduced in 1879 as part of the "english set of units"
(Wikipedia is sometimes useful).

12. ### charlesGuest

I certainly remember the poundal.

The various old english measures: chain, rod, quarter, peck, etc, were, of
course, very useful to teach children arithmetic since they all came with
different bases.

and of course you can measure viscosity in Acres per year - if you want to.

13. ### Ian JacksonGuest

You forgot the poles and perches, the bushels, and of course, the LSD.

14. ### Guest

| charles wrote:
|>> says...
|>>> It is necessary to distinguish between mass and force but they are both
|>>> measured in pounds in the english system.
|>
|>> The "English" system uses the "stone" as the measurement of mass.
|>> The pound ('lb') is the unit of *FORCE*.
|>
|> The 'Stone' is a unit of mass, not "The unit of mass"
|>
|> All the engineering I ever learned in the British (Imperial) system used
|> pounds.
|
| I always thought the British pound was a unit of currency.

That's why I never wanted to carry around the British currency. It can be
quite a chore to carry 50 pounds in your pocket

15. ### charlesGuest

that saying must be some years old.

A pint's now about three pounds ;-(

16. ### Andrew GabrielGuest

Also a US pint (16 fl.oz) is smaller than an Imperial pint (20 fl.oz),
so that would make beer more expensive in the US ;-)

17. ### David LesherGuest

Just wait until you run into BTU's....

18. ### David LesherGuest

The pole pigs here [7200v in/120-240 out] are fixed tap, I'm told. Saves
money. I think they are fused at 10A in. Older ones may have settable taps.
Capacitors are in various places but we also have three 7200V line
regulators a block away, one on each primary phase. They are
auto-transformers, with allegedly auto-controlled tap changers, much as
the other poster described. [But his description is more complex than
I recall from the class covering same. The essential aspect was you
CAN short two taps together while switching; the inductance limits the
current change while you do..]

I say "allegedly" as twice now, the regulators have stuck and my UPS
woke me up at 2:30AM with notices it was disconnecting from the now-128v+
line. I solved the issue that night by putting a Variac in the line
ahead of it, and cranking it down.

It took multiple calls and finally PSC [oversight agency] complaints
to get PEPCO to fix the damn thing.

I envy EU houses. If we had regular 240V/30A+ outlets, I'd be able to
buy a snowblower with real guts. The [email protected] ones are wimpy.

19. ### Guest

|
|
|>All distribution transformers, sometimes called "pole pigs", that I
|>to as taps. Usually they are an actual bolted "tap" and you open the
|>transformer and set the output voltage by making the proper tap
|>connection when the transformer is installed and frankly it is usually
|>ignored thereafter.
|
| The pole pigs here [7200v in/120-240 out] are fixed tap, I'm told. Saves
| money. I think they are fused at 10A in. Older ones may have settable taps.
|
|>The other "cans" you often see on poles are capacitors used to adjust
|>the power factor on some secondaries.
|
| Capacitors are in various places but we also have three 7200V line
| regulators a block away, one on each primary phase. They are
| auto-transformers, with allegedly auto-controlled tap changers, much as
| the other poster described. [But his description is more complex than
| I recall from the class covering same. The essential aspect was you
| CAN short two taps together while switching; the inductance limits the
| current change while you do..]
|
| I say "allegedly" as twice now, the regulators have stuck and my UPS
| woke me up at 2:30AM with notices it was disconnecting from the now-128v+
| line. I solved the issue that night by putting a Variac in the line
| ahead of it, and cranking it down.
|
| It took multiple calls and finally PSC [oversight agency] complaints
| to get PEPCO to fix the damn thing.
|
| I envy EU houses. If we had regular 240V/30A+ outlets, I'd be able to
| buy a snowblower with real guts. The [email protected] ones are wimpy.

So put one in.

20. ### David LesherGuest

The issue is not the outlets available in my house [but I sometimes wish
for 3 phase..].

Rather, it's the ready market of consumer appliances that would take
advantage of them. That would require many houses to have them.