Why always MVA rating in electric machines?

Replies

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  chirag_kotadia

  Re: Why always MVA rating in elect. machines?
  
  VA rating is the one that is indicating the complex power which contains reactive power and active power. Watt rating neglects the power factor between current and voltage while VA rating account this. Hope u r clear.
• 

  cranky

  chirag_kotadia

  VA rating is the one that is indicating the complex power which contains reactive power and active power. Watt rating neglects the power factor between current and voltage while VA rating account this. Hope u r clear.

  Like chirag mentioned VA refers to Volt amperes rating and W refers to watt.But I guess you mentioned it incorrectly.Watt takes into account of powerfactor.We have W=VA * (power factor)
  
  Since the load may vary and hence the power factor(if resistive,more power factor and inductive,the otherwise) it becomes difficult to rate since power becomes dependent on load which is not what we wan't to denote.Hence,VA is preferred.
  
  Also,The electricity boards insist on keeping power factor high.
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  vishu445

  adding to cranky, VAR stands for volt ampere reactive which is the measure of the apparent power. This power just fluctuates between the conductors and has no effect on the load. Also it earns no revenue.
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  vibhor_one

  can you tell me something more var?
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  cranky

  Even i would like to know..Var is Apparent power..mathematically equal to VIsin@
• 

  vishu445

  Apparent Power is measured in terms of VAR. It will more clearer to visualize VAR on Power Loci Transmission Line. For example, consider the power circle diagram of sending end. The two coordinate axes are of MW(real power) and MVAR(apparent power). From here we can can conclude all the transmission parameters vary in terms of both real and apparent power. Also remember the fact that effects of apparent power are confined to transmission and has no effect on load.