230v line to neutral single phase IEC motor

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example
DC motor (same principles apply)
100 HP (200 V, 400 A armature, eff ~ 93%)
100 rpm (yes, they are made, common for elevators)
3 ft dia. drum
drum speed = Pi x D x rpm= 940 ft/min 15.7 ft/sec

shaft torque = 5252/100 x 100 = 5252 lb-ft

force at drum radius = T/r = 5252 lb-ft /1.5 ft = 3500 lb
assume no slip, this could lift 3500 lb at 15.7 ft/sec
assume 5% slip and load to 95% SF, derate to lift 3150

unless designing a motor I don't care about flux, etc., just give me the basic electrical and performance data
 
Ingenieur said:
not for what we are discussing
a motor driving a load

if we know: v, I, pf, eff we know shaft power
does not matter what is going on in the motor (that is reflected in the above data)
add in rpm we know torque

from this we can determine the force on a belt
the volume/head capabilities of a pump
etc.
Click to expand...

We can, but lowering the voltage will reduce the available torque. For an over sized motor this will never be an issue, but for one that is undersized it may show up:


http://aceee.org/files/proceedings/2001/data/papers/SS01_Panel2_Paper27.pdf
 
Ingenieur said:
example
DC motor (same principles apply)
100 HP (200 V, 400 A armature, eff ~ 93%)
100 rpm (yes, they are made, common for elevators)
3 ft dia. drum
drum speed = Pi x D x rpm= 940 ft/min 15.7 ft/sec

shaft torque = 5252/100 x 100 = 5252 lb-ft

force at drum radius = T/r = 5252 lb-ft /1.5 ft = 3500 lb
assume no slip, this could lift 3500 lb at 15.7 ft/sec
assume 5% slip and load to 95% SF, derate to lift 3150

unless designing a motor I don't care about flux, etc., just give me the basic electrical and performance data
Click to expand...

But voltage and frequency effect flux.


But answer this for me in math or terminology: What if I took a 115 volt 60Hz 1 HP motor and ran it at 400 Hz 115 volts driving a 0.65kw load ?
 
Ingenieur said:
not true
why is it constant?
you lack understanding
you are not alone

power is power lol
Click to expand...
In this case, the power is proportional to the speed. That means the same torque at both speeds.
I suppose one could be pedantic and say that it is slightly lower at 60Hz. It's under1%. That could be accounted for by increased windage and friction.
 
mbrooke said:
But voltage and frequency effect flux.


But answer this for me in math or terminology: What if I took a 115 volt 60Hz 1 HP motor and ran it at 400 Hz 115 volts driving a 0.65kw load ?
Click to expand...

may burn up
assuming it has the caps included
It would increase current by (1/(2PiC60)) / (1/(2PiC400)) = 400/60 or 6.67 times (ignoring R and L)
 
Ingenieur said:
P = v x I
where does freq fit in?
it lowers the Z and allows more current
Click to expand...



With flux density. Again, think a 480 volt 60Hz motor on 400 volts 60Hz. It may draw more current, but it still lacks proper torque. Any HVAC tech can tell you when happens when an AC unit ages and its on a low voltage supply. Hard start kit comes out :thumbsup:
 
Besoeker said:
In this case, the power is proportional to the speed. That means the same torque at both speeds.
I suppose one could be pedantic and say that it is slightly lower at 60Hz. It's under1%. That could be accounted for by increased windage and friction.
Click to expand...

WHY is torque ~ constant?
it usually is not
it is inversely proportional to speed
P = T w or T = P/w

WHY does power increase with speed (freq) in this case?
 
Ingenieur said:
WHY is torque ~ constant?
it usually is not
it is inversely proportional to speed
P = T w or T = P/w

WHY does power increase with speed (freq) in this case?
Click to expand...
In this case you have 1.5kW at 1450rpm and 1.8kW 1t 1730rpm.
So speed and power go up by a factor of 1.2 or very close to that.

Now look at the equation you provided.

P=Tω

Absolutely no disagreement whatsoever with that. It's a relationship I've used it throughout my professional career for many applications.
So, if P and ω both go up by the same factor, as in this particular case, that will only work if T remains constant.
 
Besoeker said:
In this case you have 1.5kW at 1450rpm and 1.8kW 1t 1730rpm.
So speed and power go up by a factor of 1.2 or very close to that.

Now look at the equation you provided.

P=Tω

Absolutely no disagreement whatsoever with that. It's a relationship I've used it throughout my professional career for many applications.
So, if P and ω both go up by the same factor, as in this particular case, that will only work if T remains constant.
Click to expand...

obviously the ratio's work in this case
but why?
why does I (and therefore power) increase with rpm?

torque is not constant for a given freq for this motor, look at the data sheets previously posted
 
240V in this country is 240V line to line. Don't think of it as 2x120V, unless you intend on using 120V for something. If you are using the 240V, any line to neutral voltage level is inconsequential.

When you have 3 phase 240V, it is, again, 240V line to line. SOME 240V Delta services have a winding that is tapped in the center to allow for a limited amount of 120V but that is not always the case.
 
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Besoeker said:
Thank you. That was my simple point.
Seems to have been hard work getting there.......
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Your 'point', although simple, adds no understanding of the system
it is so obvious it does not bear mentioning and does not hold true in general
why does current (hence power) increase?
does this hold true for a 3 ph squirrel cage/induction motor?
why not? (Hint: Z goes up i goes down, the opposite)

here's the whole quote
no selective editing to cherry pick and deflect in order to avoid answering a basic question

Ingenieur said:
obviously the ratio's work in this case
Click to expand...
Ingenieur said:
but why?
why does I (and therefore power) increase with rpm?

torque is not constant for a given freq for this motor, look at the data sheets previously posted
Click to expand...
 
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Besoeker said:
Now, having seen the nameplate, you could have done that a lot more simply.
The power is proportional to speed in both cases.
That can only happen with constant torque.

No need to make it any more complex than that.
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If you had read the previous posts you would have seen that was already noted
although meaningless in achieving an understanding of the system
still does not explain why i increases with freq?

Ingenieur said:
as rpm increases power goes up (per nameplate)...proportional +20%

but since rpm increases T decreases...inversely proportional +1/20%

net result is ~ the same
Click to expand...
 
Ingenieur said:
Your 'point', although simple, adds no understanding of the system
it is so obvious it does not bear mentioning and does not hold true in general
why does current (hence power) increase?
does this hold true for a 3 ph squirrel cage/induction motor?
why not? (Hint: Z goes up i goes down, the opposite)

here's the whole quote
no selective editing to cherry pick and deflect in order to avoid answering a basic question

Click to expand...
The OP want's to know what the motor will do, not why it will do it.
 
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