I used a little bit of brute force approach. It is probably not the most intuitive approach, but gives a quantitative answer whose validity you are welcome to judge for yourself.
You gave us FLA, HP, FLPF. From that data we can also calculate FL Eff =0.9455.
Using the attached spreadsheet (requires analysis tookpak installed), I fitted the following equivalent circuit parameters to your data:
R_NL = 40.27231006 ohms Resistor simulate portion of No-Load losses - connected direct in parallel with the source
R_1 = 0.011574312 ohms Stator Resistance
X_1 = 0.179466053 ohms Stator Reactance
R_2 = 0.01157434 ohms Rotor Resistance refd to stat - Should be ROUGHLY FullLoadSlip* 3*VLN^2/FullLoadWatts
X_2 = 0.177699823 ohms Rotor reactance refd to stator
X_M = 3.66270788 ohms magnetizing reactance
By the way I assumed a slip of 0.01.... it is not a critical assumption because R2 will vary to make up for any errors in estimating slip to keep R2/s nearly correct.... there are two other resistances in the model that can float to keep efficiency correct without imposing any constraint on R2.
The solution varies the equivalent circuit parameters to find a "weighted" best match to the target specifications. The power factor, efficiency, and full load current were weighted most heavily.
Since there is are more parameters available than input data, there is some flexibility in the solution. Using very low weighting factors I weakly imposed three thumbrules:
X2/X1 = 1.0
R2/R1 = 1.0
X1/XM = 0.05
The results comparing calculated performance of the model vs target performance specification gives outstanding agreemetn:
FullLoadAmps = 232.9999894 Amps Target= 233 FractError= -4.54736E-08 Weight= 1
FullLoadEff = 0.945497223 none Target= 0.945530445 FractError= -3.51364E-05 Weight= 10
FullLoadPF = 0.84489616 none Target= 0.845 FractError= -0.000122887 Weight= 10
FullLoadPower = 148298.9084 watts Target= 149200 FractError= -0.006039488 Weight= 0
X2overX1 = 0.990158416 none Target= 1 FractError= -0.009841584 Weight= 0.01
R2overR1 = 1.000002482 none Target= 1 FractError= 2.48166E-06 Weight= 0.01
X1overXm = 0.048998189 none Target= 0.05 FractError= -0.020036217 Weight= 0.01
I will tell you from experience, R2/R1 is not very critical due to presence of R_NL.
X2/X1 is not critical for reasons that can be seen by examining the simplifying assumptions used in the Ossanna diagram. The derivation of the Ossanna diagram starts by moving Xm to the line side of X1. How can we do it!!??!. The answer can be roughly seen by ignoring R1 and looking at the thevinin equivalent source of the circuit consisting of the voltage source, the leakage reactances and the magnetizing reactance. In realistic situations we see that thevinin equivalent is practically unchanged. What makes it happen? Simply that Xm>> X1 and Xm>>X2. If you work through the thevinin equivalent circuit with any of the leakage impedances moved to either side of the equivalent circuit, and then simplify the results using Xm>>X2, you will always end up with the same thevinin circuit which has
Voc ~ Vs
Isc ~ Vs/(X1+X2)
Rth = Voc/Isc
Since X1 and X2 appear only as a sum and not individually, it doesn't matter what their ratio is... only what their sum is.... we could lump all the total leakage reactance in either one (X1 or X2) and the thevinin circuit characteristics would not change much (based on the fact that Xm is so much larger than either one).
This observation helps simplify the vector diagram for the Ossanna diagram, but also tells us the assumtion X2/X1 is not critical.
X1/Xm is more of a critical assumption because it gets directly at the subject we have been talking about, and it has a dramatic effect on the computed no-load current in this problem. I noticed if you put the target at 0.1 or 0.2, the program still wants to drag it down to 0.05. If you put the target down below 0.5 the program drags the solution toward non-credible results.
I think the ratio 0.05 is a credible ratio based on looking at similar size motors and certainly the design presented above is a very plausible equivalent circuit model of the motor from no load to full load (there may be others).
Using the above equivalent circuit parameters, we can quickly calculate the no-load current as
NLA = VLN / (Xm + X1) = 277 / (3.66270788 + 0.179466053) = 69.1 Amps
if you add in the R_NL portion, it is 69.5 amps... not an important detail.
The bottom line, 70A would be my best prediction from the nameplate data you gave, and with a slightly different specified X1/XL it can easily change to 60A. I don't see any reason to suspect your measurement.
This is just one approach to the problem of estimating no-load currents from nameplate data. It may seem like overkill, but it's easy once you get the hang of the spreadsheet (that can be used for many many different tasks besides this). A little bit of vector thinking will probably give more insight into the behavior along the lines of the diagram linked by Gunnar.
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