why do we use LPF wattmeter not UPF in the experiment of no load and blocked rotor test of 3phase slipring induction motor?
Answer Posted / saurabh wani
We use LPF only for no load test because at no load only reactive component of current flows in any machine. In 3 phase induction motor magnitude of reactive component current is more because of air gap. So power factor under no load operation is low and we use LPF wattmeter . If we use here UPF then it will give reading at time of starting only and after 3to 4 sec pointer will stable at zero no deflection.
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