230v line to neutral single phase IEC motor

[Ingenieur]

Manual page 47
http://www.leroy-somer.com/_popup/en/downloads/catalogues/?id=351

Version PR with starting cap/relay

rated for 120/240 3W 60 Hz
UL Listed for use in the USA

Rated no load speed
1500 50 Hz
1800 60 Hz

 

[kwired]

Motor name plate

Motor is designed for 50 or 60 Hz, still will have different speeds for each, though that can be compensated for with gear/pulley reduction in anything not direct coupled to the load.

 

[mbrooke]

Every single phase motor I have ever seen you could go up or down a size in cap with no real ill effect.

Just making sure, Xc=1/ 2x3.14xfxc plays a funny role.

 

[ActionDave]

Just making sure, Xc=1/ 2x3.14xfxc plays a funny role.

Pie are squared times the angle of the bifocal divided by real world ups and downs leads me to be 99% sure that motor manufactures pick a capacitor size that is right in the middle of what works.

 

[kwired]

Pie are squared times the angle of the bifocal divided by real world ups and downs leads me to be 99% sure that motor manufactures pick a capacitor size that is right in the middle of what works.

Run capacitors are more precision, but you can get away with a pretty wide tolerance with start capacitors. In fact that is all a "hard start" device for hermatic refrigerant compressors is - a higher value capacitor temporarily placed across the run capacitor to increase the capacitance value during starting

 

[ActionDave]

Run capacitors are more precision, but you can get away with a pretty wide tolerance with start capacitors. In fact that is all a "hard start" device for hermatic refrigerant compressors is - a higher value capacitor temporarily placed across the run capacitor to increase the capacitance value during starting

I agree. I would always do my best to make sure a run cap stays the same as factory original. My thinking was going along the lines of motor makers are pretty good at making a product that will work in diverse environments.

 

[Ingenieur]

Motor name plate

thanks
rated shaft P
50 Hz 1.5 kw or 2 HP
60 1.8 kw or 2.4 HP
so fully rated at 60

Torque
50 Hz 7.25 lb-ft
60 Hz 7.3 lb-ft
essentially the same
so torque remains constant

shaft P = v x i x pf x eff (v x i = electrical power)
eff = Shaft P / (v x i x pf)
50 Hz 80%
60 Hz 79%

 

[mbrooke]

Pie are squared times the angle of the bifocal divided by real world ups and downs leads me to be 99% sure that motor manufactures pick a capacitor size that is right in the middle of what works.

Ok, just making sure :thumbsup: Id hate the OP put this in service only to find out latter the caps were not giving the right current to the start windings.

 

[mbrooke]

thanks
rated shaft P
50 Hz 1.5 kw or 2 HP
60 1.8 kw or 2.4 HP
so fully rated at 60

Torque
50 Hz 7.25 lb-ft
60 Hz 7.3 lb-ft
essentially the same
so torque remains constant

shaft P = v x i x pf x eff (v x i = electrical power)
eff = Shaft P / (v x i x pf)
50 Hz 80%
60 Hz 79%

Why would the torque be the same for 60Hz 230 volts? Id imagine with the reduced voltage in relation to the frequency torque would be less?

 

[Ingenieur]

Why would the torque be the same for 60Hz 230 volts? Id imagine with the reduced voltage in relation to the frequency torque would be less?

P = T w where w = (2 Pi n) and n = rev/sec
convert to HP and rpm
(60 sec/min x 550 ft-lb/sec) / (2 Pi rad/rev) = 5252

plug/rearrange
T = 5252/rpm x HP
you can check my math, perhaps I made an error

In our case
as rpm increases power goes up (per nameplate)...proportional +20%
but since rpm increases T decreases...inversely proportional +1/20%
cancel
net result is ~ the same

 

[Besoeker]

One question though. If the motor is purely for 50Hz, at 60Hz those caps might over drive a winding.

Accprding to the OP

It is a Leroy Somer 230v single phase 50hz, 60hz, 1.8kw.

From that, one might reasonably infer that it is not purely for 50Hz.

 

[Besoeker]

Why would the torque be the same for 60Hz 230 volts? Id imagine with the reduced voltage in relation to the frequency torque would be less?

In general, it wouldn't. That's why you get constant torque and constant power ranges on VFDs.

 

[Besoeker]

Please post the name plate

euro 3 phase
400 vac paper std which is 230 to n
UK actual is 415 iirc 240 to n

It's been 400V_LL and 230V_LN for decades.

A pic of the nameplate would be helpful, I agree.

 

[mbrooke]

Accprding to the OP


From that, one might reasonably infer that it is not purely for 50Hz.

I know, missed that tid bit :ashamed1::ashamed1:

 

[mbrooke]

P = T w where w = (2 Pi n) and n = rev/sec
convert to HP and rpm
(60 sec/min x 550 ft-lb/sec) / (2 Pi rad/rev) = 5252

plug/rearrange
T = 5252/rpm x HP
you can check my math, perhaps I made an error

In our case
as rpm increases power goes up (per nameplate)...proportional +20%
but since rpm increases T decreases...inversely proportional +1/20%
cancel
net result is ~ the same

I think there is more math to that being left out...like magnetic flux...but could be wrong here. Page 3 is what I have in mind:


https://www.google.com/url?sa=t&rct...sg=AFQjCNE93d6SfjrWrJSvcKcyoGODbDpPtw&cad=rja

 

[Besoeker]

I know, missed that tid bit :ashamed1::ashamed1:

No problem.
As my late, great friend Tommy was fond of saying:
"The man who never made a mistake never made anything."

 

[Ingenieur]

for the same v 230 the current goes up at 60 Hz (8.4 to 10) (i is ~ to instantaneous torque)
why?
the Z of the motor must decrease for I to increase
which is the larger percentage/influence of total Z: the C of the motor or the L (ignore R)
if f increases what happens to each?

the motor draws more i so makes more power (v being constant) AND more torque at the SAME rpm
but since speed increases the torque decreases to the 50 Hz rating

 

[Ingenieur]

I think there is more math to that being left out...like magnetic flux...but could be wrong here. Page 3 is what I have in mind:


https://www.google.com/url?sa=t&rct...sg=AFQjCNE93d6SfjrWrJSvcKcyoGODbDpPtw&cad=rja

no
that is the fundamental torque/power relationship
applies equally to a gas engine, a bicycle, or turning a wrench

if we know (for an electrical motor)
v
i
pf
eff
we know net or shaft power
if we know that AND rpm we know torque

 

[Besoeker]

for the same v 230 the current goes up at 60 Hz (8.4 to 10) (i is ~ to instantaneous torque)
why?
the Z of the motor must decrease for I to increase
which is the larger percentage/influence of total Z: the C of the motor or the L (ignore R)
if f increases what happens to each?

the motor draws more i so makes more power (v being constant) AND more torque at the SAME rpm
but since speed increases the torque decreases to the 50 Hz rating

Look at the cos phi. What does that tell you?

 

[mbrooke]

no
that is the fundamental torque/power relationship
applies equally to a gas engine, a bicycle, or turning a wrench

if we know (for an electrical motor)
v
i
pf
eff
we know net or shaft power
if we know that AND rpm we know torque

Then how or why does a 480 volt 60Hz motor produce less torque on 400 volts 60Hz?