Motor load calculation

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Besoeker said:
Nope. Common mistake.
Power is power. You may express it in different units but it is still power.
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Wrong...again


Forms
mechanical
electrical

differing in magnitude by motor efficiency

power = energy/time or rate of energy transfer
forms of energy (and hence power since the denominator is common, ie time)
electrical, chemical, mechanical, etc

common mistake
 
Besoeker said:
The 249W is correct for output power or shaft power as it's sometimes called.
The 828 is the input VA, not power. Important distinction. It takes account of motor power factor and efficiency.
The 3.6A tells you how to ought to rate conductors and other circuit components.
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S in va is the TOTAL POWER
S = P + jQ
S total power in va
P real power in Watts
Q reactive power in var

the system must be sized for S since a Q current actually flows (if pf ne 1)
 
Ingenieur said:
Wrong...again


Forms
mechanical
electrical

differing in magnitude by motor efficiency

power = energy/time or rate of energy transfer
forms of energy (and hence power since the denominator is common, ie time)
electrical, chemical, mechanical, etc

common mistake
Click to expand...
Power is power.
No ifs, no buts.
You should understand that.
 
Besoeker said:
Power is power.
No ifs, no buts.
You should understand that.
Click to expand...

Energy is energy lol

It has different forms
you should understand that
shaft power
brake power
real power
reactive power

grab an energized conductor
grab a spinning shaft
2 distinct results
Both due to power, 2 different forms
 
Besoeker said:
VA is not a measure of power.
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Absurd
Don't they rate POWER transformers in va?
lol

The complex power is the vector sum of active and reactive power. The apparent power is the magnitude of the complex power.
Active power, P
Reactive power, Q
Complex power, S
Apparent power, |S|
Phase of current, φ
 
Ingenieur said:
Absurd
Don't they rate POWER transformers in va?
Click to expand...
They do, but they also rate some control transformers in VA, so that means that VA is a unit of control? :)

The VA rating of a power transformers does not, by itself, tell you how much power that transformer can supply. You also need to know the PF of the load.
 
Besoeker said:
But energy is not power. It is power times time.
Click to expand...

as I stated power = work or energy / time
joule/sec


Keep digging
various forms of power
real or active
total or complex
reactive
electrical
mechanical
chemical

force is force lol
energy is energy lol
 
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GoldDigger said:
They do, but they also rate some control transformers in VA, so that means that VA is a unit of control? :)

The VA rating of a power transformers does not, by itself, tell you how much power that transformer can supply. You also need to know the PF of the load.
Click to expand...

weak

really?
S va = P watt + jQ var

you need pf to determine active power not the total power
they do not rate transformers in watts lol
a transformer can supply all reactive power in var, no watts
pf = 0
but usually a combination
for a pf of 70% 50/50 real/reactive
if you need 1 Mw and 1 Mvar you can't supply with a 1 Mva...for long
not uncommon for motor loads

keep digging lol
 
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Power:

The rate of doing work. It is expressed in mass times distance over a period of time. Also see candle power and horsepower .

Expressed in watts (W) or kilowatts (kW), and is equal to:

or energy rate is measured in watts. It measures the rate at which power or energy is used. Power equals voltage times amps. or W = E x 1. The heavier the flow of amps at a given supply, the higher the rate at which energy is being supplied and used.

http://www.engineering-dictionary.org/Power

Energy:

Capacity for doing work.

In the simplest terms, energy is the ability to perform work. It may exist in several forms, such as heat energy, mechanical energy, chemical energy, or electrical energy, and may be changed from one form to another.

http://www.engineering-dictionary.org/ENERGY


Both definitions slightly edited by me for clarity.
 
Work = force x displacement
power = work/time
the units of work and energy are the same joules

The change in the kinetic energy of an object is equal to the net work done on the object. This fact is referred to as the Work-Energy Principle and is often a very useful tool in mechanics problem solving.
 
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Ingenieur said:
Work = force x displacement
power = work/time
the units of work and energy are the same joules

The change in the kinetic energy of an object is equal to the net work done on the object. This fact is referred to as the Work-Energy Principle and is often a very useful tool in mechanics problem solving.
Click to expand...

Yes, but the formulas for energy/work and power differ. Same base units, but time differs giving a rate for power. (I think I got that right)

http://www.easternct.edu/mathematic...cal-Science-Tables-Formulas-and-Equations.pdf
 
jumper said:
Yes, but the formulas for energy/work and power differ. Same base units, but time differs giving a rate for power. (I think I got that right)

http://www.easternct.edu/mathematic...cal-Science-Tables-Formulas-and-Equations.pdf
Click to expand...


The whole wing ding started with a comment
2 forms of power in this case
mechanical or shaft = active elec power P x eff
electrical S = P + jQ
mechanical and elec being 2 forms manifested

a third could be chemical
say you have an exlposion that releases 1 M joule in 1 sec
is that not 1 Mw of 'chemical' power
much different form than 1340 shaft mechanical HP or 1000 v x 1414 A x 0.707 (pf) elec Mw
???
all based on an innocuous statement latched onto by an internet stalker

the intent was to illustrate to the OP
elec input power in watts ne mechanical shaft power in watts
the 2 forms of power are not equivilent, they differ
 
Ingenieur said:
The whole wing ding started with a comment
2 forms of power in this case
mechanical or shaft = active elec power P x eff
electrical S = P + jQ
mechanical and elec being 2 forms manifested

a third could be chemical
say you have an exlposion that releases 1 M joule in 1 sec
is that not 1 Mw of 'chemical' power
much different form than 1340 shaft mechanical HP or 1000 v x 1414 A x 0.707 (pf) elec Mw
???
all based on an innocuous statement latched onto by an internet stalker

the intent was to illustrate to the OP
elec input power in watts ne mechanical shaft power in watts
the 2 forms of power are not equivilent, they differ
Click to expand...
Power is power. You need to get that into your daft noddle.
 
Besoeker said:
Power is power. You need to get that into your daft noddle.
Click to expand...

No need for insults pumpkin
you sound frustrated
it is ok to be wrong, as long as you accept it and learn from it
you should be used to it by now
thinking is obviously not your forte'

S in va total POWER
P in watts active POWER
Q in var reactive POWER
lol
power is power but 3 different units?
rotflmfao
 
Ingenieur said:
No need for insults pumpkin
you sound frustrated
it is ok to be wrong, as long as you accept it and learn from it
you should be used to it by now
thinking is obviously not your forte'

S in va total POWER
P in watts active POWER
Q in var reactive POWER
lol
power is power but 3 different units?
rotflmfao
Click to expand...
Nope. Power is just power.
My dog is black and white.
 
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