While measuring power in a three phase load by two wattmeter method, the reading of two wattmeter are

While measuring power in a three phase load by two wattmeter method, the reading of two wattmeter are equal and opposite, when (a) load is balanced (b) power factor is unity (c) phase angle is between 60° to 90° (d) the load is purely inductive 
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Answer :

 Option (d)  Load is purely inductive 
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In a 3-phase power measurement by two wattmeter method the reading of one of the wattmeter was zero...

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