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To truly "open circuit test" a motor as I interpret it, remove it from power, and measure the following:

* Using an Ohmmeter, measure each winding resistance.  Start from W1 to W2.  This will be some value, such as 5.1Ω.
* Measure U1 to U2 and it should be very close to the previous value; within 10% or better.
* Measure Y1 to Y2 and likewise.  If any one is greater than 10% different than the others, then that winding is damaged and running the motor could be dangerous.

* Still using the Ohmmeter, measure "across" various windings, such as W1 to U2 and vice-versa. All should measure "open" or infinite resistance (no winding there.)  My suspicion is that there are other connections not evident (motor might already be wired for star or delta configuration), and this will find those connections.  Draw these on paper to figure out how it is really wired.

* Using an Ohmmeter which can read very high Ohms (giga-Ohmmeter or "insulation tester" would be best), check the resistance between all windings and motor chassis Earth ground.  Anything seen should be 20MΩ or higher, indicating that there is almost zero electrical flow between these "hot" windings and the chassis.  If one reads substantially lower than the other (say 10MΩ), then that indicates the winding insulation is degraded and may soon catastrophically fail.  Anything under 5MΩ is bad and should not be run.

* Most consumer single-phase motors only have a thermal cut-out switch.  But three-phase motors usually have either an overall thermal switch or a (simple to complex) temperature sensor. Find a datasheet for the motor model and check the thermal sensor.  It may be normally closed, open, or some resistance value depending on temperature.  If that isn't working correctly, it will prevent the motor from running in the field application.

* If the motor has any feedback devices (generator/tach, hall sensors, resolver, encoder, etc.), try to test that according to the motor datasheet/feedback device manual.  Just try to ensure they work. A misbehaving or mis-wired feedback device can cause the motor to run erratically in the field, run backwards, accelerate instantly, etc.

If all of these "static tests" pass, then the motor is good to be run-tested, which others have described here.

P.S. Could the motor terminals be labeled U,V, and W?  There are many possibilities, but most frequently these three letters are used for motors today.