dual voltage AC motors query

[morrisman]

These modern 3 phase dual voltage motors 240 / 415 are apparently made this way because different countries use different voltage standards , the manufacturers do it in order to save costs

Question: are the stator windings (1.) tapped for the dual voltage , eg a twin set of terminals , or, (2.) is it just a case of connecting the windings in either delta ( 240 ) or star (415) .

If my second theory is correct , So in Delta mode, the windings exhibit half the impedance of star mode..is that correct .

MIKE

[jack620]

Hi Mike, in star mode you have 2 sets of windings in series for each phase, so they can cope with the higher voltage. In delta there is one winding per phase. I'm not sure about your theory because in delta you also have the other two windings in series across the winding in question. Hard to explain. Image one winding in parallel with 2 windings in series. The impedance calculation gets a bit more complicated. Maybe one of the gurus will be along shortly to clarify.

[RayG]

Hi Mike,

No, they don't do it to lower costs... the cost is no different, it's just a different way of making the connections to the motor windings.

Whether you wire it in 415v star or 240 delta the voltage across the stator windings is the same.

For a 415v star connected motor the voltage across the stator windings to neutral (the star point) is 240v..

The impedance of the windings is the same.

Regards
Ray

[morrisman]

Hi Mike,

No, they don't do it to lower costs... the cost is no different, it's just a different way of making the connections to the motor windings.

Whether you wire it in 415v star or 240 delta the voltage across the stator windings is the same.

For a 415v star connected motor the voltage across the stator windings to neutral (the star point) is 240v..

The impedance of the windings is the same.

Regards
Ray

Ok got it ..... thanks