Isolation Transformer

[Love4sound]

Dear Fm’s

I am planning to get an isolation transformer for my HT set up from vertex. At present I have a 5kv vertex servo stab. Plan is to power the isolation transformer using Vertex servo stab and placing it next to the vertex inside the HT room and connect all my HT gears to the isolation transformer. I have no idea on the noise levels of isolation transformers. My MLP will be 7-8 feet from both servo stab and isolation transformer. Kindly advise on the noise levels of isolation transformer.

 

[OM_2K19]

Why not opt for Online UPS? It will make your chain even simpler. The output of an online UPS is derived from the standby battery (galvanic isolation); hence it's even better than the Mains, depending on the model. The typical noise level is around 25/30db from a meter distance.

 

[Love4sound]

Why not opt for Online UPS? It will make your chain even simpler. The output of an online UPS is derived from the standby battery (galvanic isolation); hence it's even better than the Mains, depending on the model. The typical noise level is around 25/30db from a meter distance.

Ok main reason for me to think about isolation transformer is I am getting some hum sound which is intermittent. This must be due to some device in my house or flat inducing noise in the mains. Next is neutral line is faulty and voltage between N-E is 20-50V. So vertex suggested to try an isolation transformer. Online ups will be much more expensive and isolation transformer may serve the purpose in my case.

 

[OM_2K19]

Ok main reason for me to think about isolation transformer is I am getting some hum sound which is intermittent. This must be due to some device in my house or flat inducing noise in the mains. Next is neutral line is faulty and voltage between N-E is 20-50V. So vertex suggested to try an isolation transformer. Online ups will be much more expensive and isolation transformer may serve the purpose in my case.

Gotcha, isolation transformer comes built-in with most of the 3 phase Servo stabilizer; it's pretty rare in single-phase. However, how much it will help minimize the HUM is debatable though.

 

[Love4sound]

Gotcha, isolation transformer comes built-in with most of the 3 phase Servo stabilizer; it's pretty rare in single-phase. However, how much it will help minimize the HUM is debatable though.

Yeah true. But if the source of the hum is through the main line caused by some other devices in my home or the apartment then chances are the isolation transform will remove the hum. Once when I was standing next to the amp and speakers observing the hum for a minute it just stopped suddenly from both the PA and the speakers.It didn’t come back for a hour of my testing. So I suspected some device on the house or apartments is causing the hum and it would have been shut down when the hum went away. Another source I found out was my tv. It is causing a very loud hum like a motor. So have it unhooked now and asked LG to bring a new power chord and power supply board to test.

 

[Subbu68]

Ok main reason for me to think about isolation transformer is I am getting some hum sound which is intermittent. This must be due to some device in my house or flat inducing noise in the mains. Next is neutral line is faulty and voltage between N-E is 20-50V. So vertex suggested to try an isolation transformer. Online ups will be much more expensive and isolation transformer may serve the purpose in my case.

The neutral do have voltage w.r.t. earth. Unbalanced load in your network (I guess an apartment complex) would return a current to flow back to the x'mer and with even a less than an ohm neutral earth pit, corrosion in joints, cable resistance etc.a few amps enough to give a voltage rise. Even the earthing system may not be perfect considering the standards of installations in general.

It could be even induction from another phase.
I could see two phases running in same conduit in my apartment in India.

And the appliances with motors like mixies can be heard through audio system...every wire is an antenna.

Isolation trafos should help. Keep the output floating neutral.

Any UPS would induce switching noises i believe.

TVs are notorious due to the SMPS in them.you can't get it cleaned up. Just place a radio near it and test

And if you have inverter at home switch it off and see. Many years back went to my MIL's place. Wife's grandpa asked me to solve an issue of him having to listen to his radio outside the house. Switched off the inverter and all his stations were back. With inverter and wiring acting like a RF blocker.

 

[Love4sound]

The neutral do have voltage w.r.t. earth.

True but however don’t you think 25-50V is very high. As far as I know it shouldn’t cross 3 volts.

Switched off the inverter and all his stations were back. With inverter and wiring acting like a RF blocker.

I have done almost every tests. Please do check out the below thread. I have checked the direct neutral line from EB post with earth disconnecting everything in the apartment

My earthing is screwed

Dear Fm’s As the title suggests my earthing is all messed up. Neutral to earth reading as per IEEE standard should not exceed 3 volts for homes and 5 for industrial. Mine is always around 15-30. I contacted vertex and had their electrician inspect my grounding. As per his suggestions we...

www.hifivision.com

 

[mbhangui]

And the appliances with motors like mixies can be heard through audio system...every wire is an antenna.

Isolation trafos should help. Keep the output floating neutral.

Any UPS would induce switching noises i believe.

TVs are notorious due to the SMPS in them.you can't get it cleaned up. Just place a radio near it and test

And if you have inverter at home switch it off and see. Many years back went to my MIL's place. Wife's grandpa asked me to solve an issue of him having to listen to his radio outside the house. Switched off the inverter and all his stations were back. With inverter and wiring acting like a RF blocker.

+1 to that and also tubelights and led bulbs and led tube lights which have noisy dc-dc converters in them. There is nothing more I hate than SMPS power supplies.

 

[Subbu68]

True but however don’t you think 25-50V is very high. As far as I know it shouldn’t cross 3 volts.

I have done almost every tests. Please do check out the below thread. I have checked the direct neutral line from EB post with earth disconnecting everything in the apartment

My earthing is screwed

Dear Fm’s As the title suggests my earthing is all messed up. Neutral to earth reading as per IEEE standard should not exceed 3 volts for homes and 5 for industrial. Mine is always around 15-30. I contacted vertex and had their electrician inspect my grounding. As per his suggestions we...

www.hifivision.com

True, N-E voltages should be in the range you quoted.

I read through the other thread you mentioned quickly. I guess the issue is with the EB.

There could be some high resistance fault among two phases causing the neutral to rise. Check the phase to phase and phase to neutral voltages at your main incomer. This can give a clue.

Else the neutral earthing of EB transformer is the culprit for the reasons I wrote earlier. Not sure if you can get this to the regulator's notice.

Another culprit for your hum could be the wiring in the house. The usual malpractice of the electrical contractors - to loop the neutral whereas wiring regs all over the world says every circuit should have own neutral running to the DB. But over there they save wire and loop the neutrals. You pay for a point but they save the black wire and make a profit. When there is some motor say fridge or mixie running that obviously produce some harmonics and the interference can seep into the sensitive audio equipment. Try running a separate circuit with own neutral to the DB of your house with an extension chord. Later maybe try to reach the DB through the conduits with a separate neutral wire (possibly impossible).


I also read in the other thread about twisting wires causing issues. It is a perfectly acceptable method of jointing in the industry for wires up to like 2.5sq.mm if done properly. Having worked in India I can imagine what's happening there. One thing not used is the heat shrink insulation. Electricians use the normal insulation tape and stretch it over the wires. This gets undone over a period of time and water seeps in.

And copper or steel in earthing pit does not matter. Copper corrodes less, hence longer life. Earthing is basically to conduct away the fault current and magnitudes can be in the range of kA. So the material becomes immaterial if it is sized properly to meet the thermal requirements.

Earth resistance is the interface resistance between the metal surface and the general earth. Chemical earthing as they say is used in very dry areas and rocky places - basically is bentonite clay mixed with some additives to enhance conductivity as it absorbs and retains moisture from water seeping in to the ground as well as fills the voids (air is an insulator). They drill the rock, fill with the so called chemical and insert the earth rod. For Chennai with the clayey soil it may not add value.

 

[Subbu68]

Forgot to add..

There is an underlying danger to the public in the neighborhood. With 30-50V at the EB neutral point, a wet person (say from rain) accidentally touching the neutral can reach Indarlokam. It can be even a EB technician trying to repair something during a rain.

100mA is the typical fibrillation current for a 70kg man and wet person hand to foot is like 300 Ohm. So 50V and it's 160mA - fry...

 

[aeroash]

The usual malpractice of the electrical contractors - to loop the neutral whereas wiring regs all over the world says every circuit should have own neutral running to the DB.

Out of curiosity, and having zero grasp on this subject, if a faulty equipment is carrying harmonics back to the DB Neutral, won't it end up carrying noise to all the other neutral wiring? I'm assuming Neutral being connected via Bus Bar at the DB.

 

[Subbu68]

Out of curiosity, and having zero grasp on this subject, if a faulty equipment is carrying harmonics back to the DB Neutral, won't it end up carrying noise to all the other neutral wiring? I'm assuming Neutral being connected via Bus Bar at the DB.

Ideally, the current from the load should go back to DB neutral > transformer neutral > earth > generating station. But with looping of neutral it could affect all others. My interpretation is the circuit has a resistance that you cannot avoid. A noise producer sharing the same neutral would send the current to the DB of course, but the harmonic voltage due to the circuit resistance to the DB cause interference in others in the same circuit?

I have not had this experience in UAE where I live. Every circuit ends up with a neutral at the DB. Even if the TV is on, the radio on another circuit is not affected. Switch on a/c no issues, so too mixies or fridges. BTW, I just replied to Amit on a PM, my TV used to cause hum in my stereo when I connected with RCAs. Even if I switched the input to CD on my preamp or changed the input on the amp from Input 1 (pre to amp) to Input 2 (my DAC) it was in the background augmented by Klipsch's horns. I isolated the TV with an el cheapo optical DAC and the hum vanished.

Even in the main substations where the harmonics, noise and such devils can easily originate, there is no issue with the stations controls or other sensitive equipment there.

I would consult with my colleague who has worked a lot in the industrial set up and also produced the wiring regs for Abu Dhabi. An interesting subject opened up for further study.

 

[Love4sound]

Another culprit for your hum could be the wiring in the house.

There are two hums and one can be ignored while the other cannot be ignored. As you said the hum can be due to wiring or some device within the flats which can be eliminated by isolation transformer. Even if not I ndon’t think it’s going to be a problem interms if performance or durability of the device. The another hum is caused by my Tv. It make my Pa scream as if it’s going to vibrate and explode. The second I disconnect the tv it stops.

Try running a separate circuit with own neutral to the DB of your house with an extension chord. Later maybe try to reach the DB through the conduits with a separate neutral wire (possibly impossible).

I guess you are suggesting to try this method so we can have an open circuit test meaning no connection with flats and direct neutral line. We tried this by taking a wire directly from the EB post and with earth wire which was also disconnected completely from our circuit.For 3 months have done all the test and also installed new earth rods. All tests leads to faulty neutral line. Only time the N-E is at 1-3V is when there is a power cut and running on inverter

 

[Subbu68]

There are two hums and one can be ignored while the other cannot be ignored. As you said the hum can be due to wiring or some device within the flats which can be eliminated by isolation transformer. Even if not I ndon’t think it’s going to be a problem interms if performance or durability of the device. The another hum is caused by my Tv. It make my Pa scream as if it’s going to vibrate and explode. The second I disconnect the tv it stops.

I guess you are suggesting to try this method so we can have an open circuit test meaning no connection with flats and direct neutral line. We tried this by taking a wire directly from the EB post and with earth wire which was also disconnected completely from our circuit.For 3 months have done all the test and also installed new earth rods. All tests leads to faulty neutral line. Only time the N-E is at 1-3V is when there is a power cut and running on inverter

I think we crossed with the replies. My TV also does the same with RCA connection. With Klipsch's horns it is unbearable. An el cheapo Optical DAC resolved it. SMPS inside.

If you have tried with separate neutral, then the issue is outside your house or flat I think. I strongly feel a test of the line and phase voltages could point to a line to line high resistance fault. With current crop of LED lamps it may not be evident but with the good old incandescent lamps a voltage unbalance could have come out for a normal person with no multimeter. Technicians will look at the brightness of the LEDs and say "Ada ponga Sir, enna problem?" Maybe try to reach out to some EB engineer who is friendly to resolve this?

 

[Love4sound]

I think we crossed with the replies. My TV also does the same with RCA connection. With Klipsch's horns it is unbearable. An el cheapo Optical DAC resolved it. SMPS inside.

For me the tv just plugged in the same socket as the amp causes this. If I connect with different socket the sound is reduced by 40-50% but still loud and doesn’t feel safe for equipment. No rca or HDMI connected.

If you have tried with separate neutral, then the issue is outside your house or flat I think. I strongly feel a test of the line and phase voltages could point to a line to line high resistance fault. With current crop of LED lamps it may not be evident but with the good old incandescent lamps a voltage unbalance could have come out for a normal person with no multimeter. Technicians will look at the brightness of the LEDs and say "Ada ponga Sir, enna problem?" Maybe try to reach out to some EB engineer who is friendly to resolve this?

Been trying it for 3 months. They are absolute garbage. First they don’t even accept 25-50V is abnormal. They are asking so what if N-EV is 20-50V. Next is they are saying only one complain from the locality so not acceptable. For that also I submitted a letter to AE with 15-16 individual signatures. For that also they are saying that I am instigating others there is a problem but actually there is no problem so can’t check.

 

[Subbu68]

Been trying it for 3 months. They are absolute garbage. First they don’t even accept 25-50V is abnormal. They are asking so what if N-EV is 20-50V. Next is they are saying only one complain from the locality so not acceptable. For that also I submitted a letter to AE with 15-16 individual signatures. For that also they are saying that I am instigating others there is a problem but actually there is no problem so can’t check.

That's absolutely crazy. You may have to wait until someone gets killed? Try with a measurement of line voltages than N-E voltage.

Not sure how it works there, is there a channel to approach the regulator? I work for Abu Dhabi regulator and anyone can raise a complaint to us if the local utility do not resolve such issues.

 

[Love4sound]

That's absolutely crazy. You may have to wait until someone gets killed? Try with a measurement of line voltages than N-E voltage.

Not sure how it works there, is there a channel to approach the regulator? I work for Abu Dhabi regulator and anyone can raise a complaint to us if the local utility do not resolve such issues.

Nope in india if you take any service from government you need to be influential to get any support from them. Also what do you mean line voltages? L-N? If so that seems to be normal. It’s within 230-240V and some times it is high around 255-260V

 

[Subbu68]

Nope in india if you take any service from government you need to be influential to get any support from them. Also what do you mean line voltages? L-N? If so that seems to be normal. It’s within 230-240V and some times it is high around 255-260V

Line voltage is the voltage between each phases - R-Y, Y-B and B-R in a 3 phase system. L-N is phase voltage.

I think you answered it. The high voltage at times indicates the unbalance. I strongly suspect some fault between lines.

If there is a chance to check the N-E voltage at somebody's place not far from your place served by another transformer. If it is normal then a benchmark for you. When I used to live in T.Nagar I have seen every street with it's transformer.

I guessed electricity distribution is private now but found it is TANGEDCO - TNEB rechristened.

 

[Love4sound]

Line voltage is the voltage between each phases - R-Y, Y-B and B-R in a 3 phase system. L-N is phase voltage.

Ok how to check line voltage?

I think you answered it. The high voltage at times indicates the unbalance. I strongly suspect some fault between lines.

Not only this but also in each phase the L-E V also keeps fluctuating. For example if L-N is 230v in one phase with L-E being 240-250V in the same phase another phase L-N will be 230V but L-E will be 205-210V. This keeps fluctuating between all the 3 phases.

If there is a chance to check the N-E voltage at somebody's place not far from your place served by another transformer. If it is normal then a benchmark for you. When I used to live in T.Nagar I have seen every street with it's transformer.

I guessed electricity distribution is private now but found it is TANGEDCO - TNEB rechristened.

Hahahaha now days where ever I go I take my multimeter with me. Every other places I checked the N-E V is 0.5-2V. Now I can’t talk this with my area EB line man. They will say load there is different. They give all the nonsense excuses and absolutely have 0 knowledge. For every complaints they just bring one tester and say sir line working see tester is glowing and next is they will show ryb phases voltage on meter. I was like complain is not this please take the multimeter and check and they get so nervous and run away

 

[Subbu68]

Ok how to check line voltage?

Not only this but also in each phase the L-E V also keeps fluctuating. For example if L-N is 230v in one phase with L-E being 240-250V in the same phase another phase L-N will be 230V but L-E will be 205-210V. This keeps fluctuating between all the 3 phases.

Hahahaha now days where ever I go I take my multimeter with me. Every other places I checked the N-E V is 0.5-2V. Now I can’t talk this with my area EB line man. They will say load there is different. They give all the nonsense excuses and absolutely have 0 knowledge. For every complaints they just bring one tester and say sir line working see tester is glowing and next is they will show ryb phases voltage on meter. I was like complain is not this please take the multimeter and check and they get so nervous and run away

Check between the R and Y, Y and B and B and R. the terminating cables on the DB or the busbars have the colours to indicate this.

L-E voltage difference is an indication of a fault on the LV distribution network of your area.

Yeah, linemen think they know every electron flowing in the network. That is the aura our forefathers created around them. Similar to compounders in clinics. As I wrote someone among them should get a shock if not die from the neutral on a rainy day.