3 phase heater help needed

[chid22]

There is a 12KW heater installed being controlled by a three phase thyristor control. There are 6 x 2kw heating elements and i am stuggling to understand the operation. There are two elements connected to each phase but then they are then all linked to a common bar on the opposite side of the elements.

But i am told that there is no neutral needed as the heaters are in a star configuration which i am struggling to understand.

Hope this makes sense any help is much appreciated

 

[roukel01]

isn't that the same as a motor wired in Y ?? Looking at the terminals in a motor, you connect to U1 V1 W1 to the 3 phases and then the U2 V2 W2 are linked together, a balanced load.

 

[telectrix]

the star point is neutral in a star configuration. i.e 230v on each phase, 0v at the star point, so each pair of the elements has 230 across them.

 

[telectrix]

what i mean to say is that in star, by applying 3 phases, the star configuration gives you a neutral at the star point without the need for a neutral from the supply

 

[armbands0]

I think you are right to struggle, if star connected, which from your description they are, then they need a Neutral.

It is unlikely that 6 resistive elements are going to be identical, so without a neutral where will the imbalence current go.

Check with the manufacturer, if they say no neutral required then you have the answer.

 

[Steve1412]

You dont need a neutral. The fact that the three elements across three phases are connected in star forms a neutral point. Although the resistance of each element maybe be slightly different ( as are the windings on a three phase motor ) they will balance near enough.

 

[Darkwood]

what i mean to say is that in star, by applying 3 phases, the star configuration gives you a neutral at the star point without the need for a neutral from the supply

Be careful with your advice Tel' as you may be confusing him more, the star configuration in a balanced load situation has no neutral current as the nature of a balanced 3ph system omits the need as no current would flow in it.. hence for a 3ph motor or as above. The star point shouldnt be referenced as the neutral point or earth tap in this situation as it is not.
My advice is for him to learn how 3ph is turned into 1ph for domestic use to understand the nature of the neutral and why it is needed then the above query may be easier for him to understand.

Dont get me wrong im clear you do understand how it all works but you explanation could lead to deeper confusion as the star point should not be referred to as the neutral point with the above example.