Triphase motors: how to differentiate "hot" & "cold" sides of wiring?

If the motor has a standard junction box on it with six power terminals, the three at one side are the "start" of each winding.

It does not matter which side you actually use, as long as you are consistent.

Generally, shorting the three terminals at one side [along the top or bottom in the diagram] and feeding the three at the other side gives "star" configuration and linking so the short circuits are between the two sides, 1-1, 2-2 & 3-3 gives delta [ie. vertical links in that diagram]..

eg. showing with links for a fixed star config - the links vertical would give fixed delta: http://www.pcbheaven.com/userpages/images/med_thum...

Trace the terminals through to the other end of the wiring.

If there is no terminal box, it gets rather difficult - I'd identify each winding then use "star" by guesswork and try feeding via a resistor bank or three high-power filament lamps with the motor mechanically disconnected.

See if it will run or even turn it by hand and feel for "cogging" (if there is not enough power to run it), swapping one pair at a time to test then swap the same one back. You can only have one wrong at worst; either two of three or all three must be in phase one way or the other..

This isn't simple. Refer to this link for diagrams:

There are 3θ motors with split windings (single winding 2 speed),

and others which are different.

https://images.search.yahoo.com/search/images;_ylt...

There is no hot and cold.

You will have six motor leads marked T₁ through T₆

Please refer to a diagram.

Joining T₁+T₂+T₃ and T₄+L₁ , T₅+L₂, T₆+L₃ gives you "Star" or "Wye".

Refer to motor starter wiring diagram, and the motor diagram.

(buy one don't build one)

Update with the motor's make and model for a better answer.

Motors usually have a plate riveted to the housing that identifies the phasing of the wires. If not, the manual for the motor has this info. If you don't have the manual, check the manufacturer's web site.