Discussion of AC mains isolation transformers

[Ralf11]

did you see @jabbr 's post on a simple power strip on eBay?

 

I got one and like it (visual basis; no tests) better than my Tripp-Lite - the outlets are rotated and closer together; it is also hosp. certified

[zilch0md]

2 hours ago, look&listen said:

Uh, I don't think "preached" is the best word. How about "suggested" or "explained" ?

 

I'm good with that, but the Swenson is my shepherd, I shall not taunt.  He maketh me to break down the leakage currents: he leadeth me beside low noise levels.  He restoreth my soul, my R&B, and every other genre.  

 

I'd better stop there, before my system gets struck by lightning.

 

[asdf1000]

48 minutes ago, zilch0md said:

 

I'm good with that, but the Swenson is my shepherd, I shall not taunt.  He maketh me to break down the leakage currents: he leadeth me beside low noise levels.  He restoreth my soul, my R&B, and every other genre.  

 

I'd better stop there, before my system gets struck by lightning.

 

 

Hilarious!

[Speedskater]

By rule, one outlet strip (distribution box) should not be plugged into another outlet strip (that's Daisy Chain or series).  Get larger outlet strips.

Don't worry about how the strips are wired internally it's those long cords that may cause the problems.

Arrange your receptacles in a way to reduce the total length of cords from any one unit to any other unit.

While almost zero length Safety Ground conductors aren't possible, the shorter the better.

 

[Johnseye]

These Topaz isolation transformers are rated for 240 and include 2 hots. Does anyone know if there's any issue with running it at 120?  Also, if a single winding is being used at 120, is the .0005 capacitance rating still accurate? I don't know that only a single winding is used at 120, I'm just guessing. 

[One and a half]

1 hour ago, Johnseye said:

These Topaz isolation transformers are rated for 240 and include 2 hots. Does anyone know if there's any issue with running it at 120?  Also, if a single winding is being used at 120, is the .0005 capacitance rating still accurate? I don't know that only a single winding is used at 120, I'm just guessing. 

Each winding is rated at 120V.

There are 2 x120V windings on the primary and 2 x 120V on the secondary.

 

Normal supply

use an iec class D breaker, don’t know the equal in Nema std.

 

120V input, bridge the two windings together on the primary 

H1 to h3

H2 to H4

Repeat bridging on the secondary 120V output.

X1 to X3

X2 to X4

hot output on x1

neutral output on X4

ground the X4 and the shield together.

Use a standard GFCI on the output.

 

Capacitance is the same regardless of the windings connections.

 

Balanced mode

Connect primary with h2 h3 shorted

connect hot to h1

neuteal to h2

 

secondary

short x2,x3, ground this point and the shield tog

hot 1 x1

hot 2 x2

use a 2 pole GFCI-important it’s a 2pole

[Johnseye]

18 hours ago, One and a half said:

Each winding is rated at 120V.

There are 2 x120V windings on the primary and 2 x 120V on the secondary.

 

Normal supply

use an iec class D breaker, don’t know the equal in Nema std.

 

120V input, bridge the two windings together on the primary 

H1 to h3

H2 to H4

Repeat bridging on the secondary 120V output.

X1 to X3

X2 to X4

hot output on x1

neutral output on X4

ground the X4 and the shield together.

Use a standard GFCI on the output.

 

Capacitance is the same regardless of the windings connections.

 

Balanced mode

Connect primary with h2 h3 shorted

connect hot to h1

neuteal to h2

 

secondary

short x2,x3, ground this point and the shield tog

hot 1 x1

hot 2 x2

use a 2 pole GFCI-important it’s a 2pole

 

Thanks!

[Speedskater]

It this type of question ever comes up about a transformer that only has a single (rather than a dual) primary. Yes it can be used at half line voltage, but the max input current remains the same, so the max VA is cut in half.

[Johnseye]

11 minutes ago, Speedskater said:

It this type of question ever comes up about a transformer that only has a single (rather than a dual) primary. Yes it can be used at half line voltage, but the max input current remains the same, so the max VA is cut in half.

 

So because this transformer has dual primaries it is still rated at 1k VA and not 500.  Good to know. 

[Johnseye]

On 1/10/2018 at 6:11 PM, One and a half said:

Each winding is rated at 120V.

There are 2 x120V windings on the primary and 2 x 120V on the secondary.

 

Normal supply

use an iec class D breaker, don’t know the equal in Nema std.

 

120V input, bridge the two windings together on the primary 

H1 to h3

H2 to H4

Repeat bridging on the secondary 120V output.

X1 to X3

X2 to X4

hot output on x1

neutral output on X4

ground the X4 and the shield together.

Use a standard GFCI on the output.

 

Capacitance is the same regardless of the windings connections.

 

Balanced mode

Connect primary with h2 h3 shorted

connect hot to h1

neuteal to h2

 

secondary

short x2,x3, ground this point and the shield tog

hot 1 x1

hot 2 x2

use a 2 pole GFCI-important it’s a 2pole

 

Can someone explain how to ground the Topaz?  I was able to get power to the outlet but it's not grounded. I have a device that tells me if an outlet is grounded. 

 

@One and a half you state "ground the X4 and the shield together."  I don't think I follow. The H side ground is attached to the chassis. The ground from the breaker box is attached to the H side ground. On the X side I had the ground going to the outlet attached to the X side ground. Clearly this is wrong as the outlet wasn't grounded. I'm not sure how to connect X4 to ground if that's what I'm supposed to do. 

[One and a half]

1 hour ago, Johnseye said:

 

Can someone explain how to ground the Topaz?  I was able to get power to the outlet but it's not grounded. I have a device that tells me if an outlet is grounded. 

 

@One and a half you state "ground the X4 and the shield together."  I don't think I follow. The H side ground is attached to the chassis. The ground from the breaker box is attached to the H side ground. On the X side I had the ground going to the outlet attached to the X side ground. Clearly this is wrong as the outlet wasn't grounded. I'm not sure how to connect X4 to ground if that's what I'm supposed to do. 

Yes, there's a screw stud on the output box on the frame of the Topaz. Wire a green ground wire with an eye type crimplug from the screw, to X4 and connect the black flying wire that comes from within the transformer also to X4. The earth point on the primary runs through to the secondary box.

The ground to the outlet remains on the screw stud , also with an eye crimplug. 

[Speedskater]

Because the Safety Ground wire should run in close proximity to the Hot & Neutral wires all the way back to the main breaker panel, one way is to replace that circuit's cable.

Don't connect to a water pipe or ground rod. That will make a huge ground loop.

[Johnseye]

On 1/13/2018 at 8:28 PM, One and a half said:

Yes, there's a screw stud on the output box on the frame of the Topaz. Wire a green ground wire with an eye type crimplug from the screw, to X4 and connect the black flying wire that comes from within the transformer also to X4. The earth point on the primary runs through to the secondary box.

The ground to the outlet remains on the screw stud , also with an eye crimplug. 

 

Thank you, that got me up and running.

[twochaudio]

.  i never know what people are talking  about.   

[Cornan]

16 minutes ago, twochaudio said:

.  i never know what people are talking  about.   

 

And you are clear as crystal?

[sandyk]

On ‎17‎/‎01‎/‎2018 at 12:11 PM, Speedskater said:

Because the Safety Ground wire should run in close proximity to the Hot & Neutral wires all the way back to the main breaker panel, one way is to replace that circuit's cable.

Don't connect to a water pipe or ground rod. That will make a huge ground loop.

 IIRC, in Au. we are no longer permitted to connect the Safety Earth to a water pipe, in part at least, due to many water pipes now being replaced by PVC pipes.

Garry ?

[One and a half]

36 minutes ago, sandyk said:

 IIRC, in Au. we are no longer permitted to connect the Safety Earth to a water pipe, in part at least, due to many water pipes now being replaced by PVC pipes.

Garry ?

From the earth stake in the ground, the cable ends up at the main switchboard with no joints. From the main switchboard, another earth cable runs to the cold water pipe if metal, so that the pipes are earthed. Yuh, no point in earthing plastic pipes, but if a plastic pipe feeds an old copper main , then that copper main needs to be earthed. The hot water copper pipes should be done as well, at the heater, would be nice, since the water heater is not classed as a continuous earthing medium. There are new rules due to be released this year, so that may all change again.

 

The old days of using the water pipe as a protective earth source connection is no longer permitted.

[Speedskater]

In the US the Safety Ground was never explicitly permitted to use a water pipe as part of it's system (I think but havn't researched). It was sort of grandfathered in as a make-do solution.

 

However an external all metal water pipe is often used as part of the grounding system to Planet Earth.

 

Note the the Planet Earth grounding system and the Safety Ground system are two separate things. And only connected together at the main breaker panel.

[Johnseye]

What are the negatives, if any, of using an isolation transformer?  Is there any possibility of one negatively impacting the sound?  In this case let's take the .0005 pF Topaz or similar model as an example.

[Speedskater]

a] What size Isolation Transformer?

b] What size audio system?

c] Placement of Isolation Transformer?

d] How is the Isolation Transformer wired?

 

Don't worry about that 0.0005 pF  stuff.

[Johnseye]

1 minute ago, Speedskater said:

a] What size Isolation Transformer?

b] What size audio system?

c] Placement of Isolation Transformer?

d] How is the Isolation Transformer wired?

 

Don't worry about that 0.0005 pF  stuff.

 

a. 1kva

b. 250va

c. on a dedicated circuit just before the outlet of the audio equipment

d. hard wired

[esmit]

1 hour ago, Johnseye said:

 

a. 1kva

b. 250va

c. on a dedicated circuit just before the outlet of the audio equipment

d. hard wired

The sounds coming from your system will most likely be better than without the isolation transformer, but the transformer might hum. 

[Johnseye]

2 minutes ago, esmit said:

The sounds coming from your system will most likely be better than without the isolation transformer, but the transformer might hum. 

 

No concerns with hum.  It does hum, but very quietly where I need my ear close to it.  It's also in a sound isolated closet so there's no concern.

 

I do notice a difference in how the music sounds with it inline.  I have an identical, dedicated parallel circuit without the transformer and can plug into that to compare.  I guess I'm looking for a more engineering or scientific explanation of what it's doing that influences the sound and if there's any chance that influence could be negative.

[Johnseye]

On 1/5/2018 at 2:04 PM, Ralf11 said:

did you see @jabbr 's post on a simple power strip on eBay?

 

I got one and like it (visual basis; no tests) better than my Tripp-Lite - the outlets are rotated and closer together; it is also hosp. certified

 

Can you link the post or model?  I've searched through Jabbr's posts but couldn't find it.

 

Thanks

[Ralf11]

GTT is the name of it