Winding Resistance of Motor

One formula is to obtain a resistance meter, and measure it.

Must one assume that each motor is suited for the same voltage, or are they different voltages for the same power?

If the rated power output of each motor is known, why is the winding resistance of any relevance, please?

sorry i could not explain my question. i met a technician if some body ask him about any three phase motor(400v 50hz 1400rpm) he always tell the resistance within a half minute this resistance is not exact but always near the exact. i want to know is there any rule of thumb. how he do that with out calculating on paper or calculator.

Maybe if they are the exact same motor from the exact same factory made in the exact same batch. There are way too many variables involved for any generalized formula to be of much use. As PWSlack said, measure it. The best value of knowing is in relation to changes over time, so record the values now, then look at it again in a year and see how much it changes. The temperature by the way must be the same as well.

The stator winding resistance depends on many factors as: voltage, frequency, velocity, slip, power factor, efficiency, insulation class [maximum permissible temperature] and other. For instance if Rstator=2*ro*lm*w1/q1 where lm=average conductor length; w1=number of turns; q1=conductor cross-section

Ro depends upon material [usual copper of 100% conductivity], temperature [insulation class] w1=pi()*dia*A/2/3/Irated where dia=stator inner diameter A=amper/cm=140-550 [usually]; Irated depends on power,p.f., eff., voltage; q1=Irated/j j=current density [usually 4-7 A/mm^2].

Briefly: only by design the motor from the beginning one may state the resistance.

But-as PWSlack already said- the design will not be the actual resistance. It is better to measure it.

the simple answer is no. what are you trying to achieve? maybe we can offer useful advice