3 wires unipolar system existance
3-wire unipolar steppers don't exist. The standard is 5 or 6.

In principle you could make a 3-wire bipolar motor, with the two windings in series, but the driver would be unpleasantly complex, and the performance of the motor would suffer, as the maximum voltage available to each winding would be reduced for a given controller power supply, and this would reduce maximum speed.