nameplate speed on induction motor??

[far243]

hi all
i want to know the nameplate speed on induction motor is full load speed or no load speed?
i know when T-s charactristic induction motor and load charactristic cross together we have definite slip and load speed,but is it equal nameplate speed?

 

[jraef]

That is the rated speed at rated slip, so if not loaded beyond what the motor is rated for, that would equate to full load speed. I know it saounds kind of fuzzy, but there are a lot of variables that still fall within acceptable limits.

"Venditori de oleum-vipera non vigere excordis populi"

 

[far243]

you assume motor in noload condition! there is a slip(speed) at this condition certainly,(ind-motor can not reach sync speed)
if we load the motor(full load), we reach to another speed !! am i correct?
what is the diffrence between two speed or which of them ic nameplate speed?

 

[BigLe]

jraef's answer was clear. the name plate speed is acquired under rated condition. with no load you can pretty much reach 99.9% of the synchrous speed if lube is good. for example if you have a 4 pole machine the synchronous speed is 1800rpm, with no load, you should be able to observe 1799 rpm or so. the name plate speed should be 175x or so.. rated slip usually falls into 2-3%.

the fuzzy part is the on the definition of load.. it's given in watts not torque. you read the name plate speed, divided by rpm-> rad/s to get the rated torque.

 

[Farkel]

Designs A,B,&C have approx. 3% slip, NEMA says below 5%, while a Design D may be 5-8%, or 8-13% slip for a squirrel caged induction motor per MG-1.

 

[aolalde]

The "nameplate speed" on an induction motor is "The full load speed"

Full load means the condition at which the motor load ( brake horsepower) is equal to the nameplate HP.

 

[DickDV]

A motor nameplate is almost always a picture of the motor at full load. Only at full load will it develop the nameplate horsepower. Only at full load will it draw nameplate current. And only at full load will its shaft speed sag down to nameplate speed.

At less than full load, the speed will rise up toward sync speed until, at no load, it will be within about 1rpm of sync speed (due to windage losses, bearing drag, and seal drag).

In fact, assuming the supply voltage is correct, the shaft slip is probably the easiest and most reliable indicator of motor load available for field trades people.

 

[far243]

Tanks all