Mukul Tyagi
Newbie level 1
My boss gave me two numbers ptq and pt2 , 480/120 volts potential transformer of 150 VA , 60 Hertz to test because it was blowing fuses .
I used 50 HZ supply for all my testing as 60 HZ is not available in the workshop .
i did the following tests , i did the ratio test and it gave results very close to the ratio is is designed for i.e 4:1
Sr.No APPLIED PRIMARY (VOLTS ) SECONDARY VOLTAGE (VOLTS ) VOLTAGE RATIO
1 50 12.56 3.98:1
2 100 25.23 3.96:1
3 150 37.78 3.97:1
4 200 50.36 3.97:1
5 256 64.4 3.97:1
I tested the DC Resistance of the primary winding and the secondary windings and it came out to be
Primary winding resistance (H1, H2) - 16.2 Ω
Secondary winding Resistance (X1, X2) - 1.5 Ω
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Conducted Insulation test @ 1000 volts and obtained the below mentioned values:
a) Between primary and secondary : 2.2 GΩ
b) Between primary and ground : 2.2 G Ω
c) Between secondary and the ground : 2.2 G Ω
also i measured the inductance of the both primary and the secondary winding , the winding not being tested was shorted while measuring the inducatance
i have forgotten the exact value but there was a difference of 1.9 mHenry between the primary of pt 1 and pt2 . the inductance of the secondary windings is the same .
i have also measured the inrush current for the pt primary keeping the secondary open , it came out to be 1.28 A for pt1 and 1.31 A for pt2 , i beleive tha fuse being used is of .5 ampere
Please suggest me what other tests i can do .
are these pt good ?
and while doing the inrush current test i applied 380 volts @ 50 Hz , how do i determine the correct voltage while working on 50 Hz , because the transformer is designed for 60 HZ, what care should i take to avoide damage to the equipment
I used 50 HZ supply for all my testing as 60 HZ is not available in the workshop .
i did the following tests , i did the ratio test and it gave results very close to the ratio is is designed for i.e 4:1
Sr.No APPLIED PRIMARY (VOLTS ) SECONDARY VOLTAGE (VOLTS ) VOLTAGE RATIO
1 50 12.56 3.98:1
2 100 25.23 3.96:1
3 150 37.78 3.97:1
4 200 50.36 3.97:1
5 256 64.4 3.97:1
I tested the DC Resistance of the primary winding and the secondary windings and it came out to be
Primary winding resistance (H1, H2) - 16.2 Ω
Secondary winding Resistance (X1, X2) - 1.5 Ω
-------
Conducted Insulation test @ 1000 volts and obtained the below mentioned values:
a) Between primary and secondary : 2.2 GΩ
b) Between primary and ground : 2.2 G Ω
c) Between secondary and the ground : 2.2 G Ω
also i measured the inductance of the both primary and the secondary winding , the winding not being tested was shorted while measuring the inducatance
i have forgotten the exact value but there was a difference of 1.9 mHenry between the primary of pt 1 and pt2 . the inductance of the secondary windings is the same .
i have also measured the inrush current for the pt primary keeping the secondary open , it came out to be 1.28 A for pt1 and 1.31 A for pt2 , i beleive tha fuse being used is of .5 ampere
Please suggest me what other tests i can do .
are these pt good ?
and while doing the inrush current test i applied 380 volts @ 50 Hz , how do i determine the correct voltage while working on 50 Hz , because the transformer is designed for 60 HZ, what care should i take to avoide damage to the equipment