DIYer logo

DIY - you may not save money, but you can earn many ... fun, new knowledge, experience, ... even money at last

Topic

star A.C. Devices
star A.C. EMI Filter
star A.C. Spectrum
star Digital Oscilloscope
star Flat Top A.C.
star Isolation Transformer - Safer Power Supply ?
star Isolation Transformer
star MCB - For Testing
star Relay - Power Failure Manual Reconnection System
star Soft Start Circuit
star Soft Start Circuit 2
star Tube Amplifier
5Z3P, 6N9P, EL34
 

Useful Info.

star AWG Vs mm
 

My AV System

star System Info.
star Testing Result 2016-5-14
star Testing Result 2014-7-27
   

Case Opening

star Cambridge Audio
CA 351C
star KEF Q300 Speaker
   

Unboxing

star 5z3p 6n9p EL34
Tube Amplifier DIY kit
star AudioQuest USB A-B Forest 1.5m
star B&W 685 S2 speaker
star WireWorld RCA Luna 7 1m
   

Other DIY

star Medeco Lock Replacement
   

 

Custom Search

Isolation Transformer
Part 10

Refer to the  Isolation Transformer Part 9, my Isolation Transformer does not match the safety expectations, there is a Voltage Potential Difference between one of the outputs and the Earth.

Last night, I tried a test, using an Ampere Meter to see whether the Voltage Potential Difference provides a dangerous electric current.

I did not take photos during the test because 100% concentration is needed for this dangerous test ... ...

This time, I disconnect all stuff, only the Isolation Transformer Coils were tested outside the Aluminum Case.

The Shielding is connected to the Earth as the test before:

Out 1 <---> Earth ( Shielding is connected to it ) : 54 V

Out 2 <---> Earth ( Shielding is connected to it ): 165 V

Results of Isolation Transformer Coils inside the Aluminum Case

You will see the  Out 1 <-> E  (54 V) is smaller ,  Out 2 <-> E  (165 V) is larger this time.
54 V+ 165 V = 219 V

For the Shielding is not connected to the Earth:
Out 1 <---> Shielding only : 114 V
Out 2 <---> Shielding only : 104 V
114 V + 104 V = 218 V

Out 1 <---> Earth only : 217 V
Out 2 <---> Earth only : 11 V
217 V + 11 V = 228 V

Strange ... ???

According to the theory, the output of the Isolation Transformer does not form a Voltage Potential Difference with Earth. But there is ... ... so, I try the dangerous test ... ... measure the Electric Current between the Out 1 / Out 2 with the Earth.

Fortunately, the Electric Current is ZERO ... ... this shows that the Voltage Potential Difference may be due to Capacitive Coupling. In other words, it is theoretically safe for touching.

Please DO NOT touch the output of the Isolation Transformer even it is THEORETICALLY safe. Please refer to here.

Moreover, the test shows that the Placement of the Isolation Transformer may affect the Capacitive Coupling effect. And one of the suggestions is that, keep the installation plate and screws insulated.

If the plate is electrically connected to the case, the electromagnetic field may also easily go around the case or form a voltage potential difference among the Isolation Transformer, the case, the earth, ... At last, worsen the Capacitive Coupling effect or the performance of the Isolation Transformer.
I am waiting for the ordered Plastic Screws for installing the Isolation Transformer Coil. I hope the Long Run Test can start as soon as possible.
Part 10 finished

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12