HV Winding Insulation

[paulengr]

So with all the spacing, is the transformer larger or less efficient?

Larger. %Z is a design choice. Say the ratio is 4:1 (480:120). We could wind it with say 1 primary turn and 4 secondary, or say 100 primary turns and 400 secondary turns. As you can guess one will have a vastly different impedance, efficiency, etc. Even with the same absolute turns we can adjust things. Say I have the same 1 primary turn but now I do it with 100 parallel one turn coils and 100 parallel secondary coils. Now I have again 10” “turns” and 400 “turns” but at 1% of the impedance. Or equivalently use a larger wire to achieve the same thing. Still with the same 480:120 ratio but vastly different impedance.

The other side of transformers is core design. Transformer losses are partly core losses and partly winding losses.

 

[mbrooke]

Larger. %Z is a design choice. Say the ratio is 4:1 (480:120). We could wind it with say 1 primary turn and 4 secondary, or say 100 primary turns and 400 secondary turns. As you can guess one will have a vastly different impedance, efficiency, etc. Even with the same absolute turns we can adjust things. Say I have the same 1 primary turn but now I do it with 100 parallel one turn coils and 100 parallel secondary coils. Now I have again 10” “turns” and 400 “turns” but at 1% of the impedance. Or equivalently use a larger wire to achieve the same thing. Still with the same 480:120 ratio but vastly different impedance.

The other side of transformers is core design. Transformer losses are partly core losses and partly winding losses.

Larger, but wouldn't this mean flux is weaker? For example, the greater the air space between the rotor and stator of an induction motor the less torque it will have.

 

[paulengr]

Larger, but wouldn't this mean flux is weaker? For example, the greater the air space between the rotor and stator of an induction motor the less torque it will have.

Yes but again you can do things to compensate. More windings gives you a greater flux. You just have to keep the ratio the same. As the total number goes up %Z and copper losses decreases while physical size increases assuming the core is adjusted too.

Switching to copper and/or using more windings to purposely decrease losses is something anyone can do when ordering a transformer to increase efficiency. Just ask to decrease %Z by 1% or so.

If you get the chance it is well worth your time to visit a custom transformer shop or at least a maintenance shop and see for yourself how these things go together. You learn a lot more seeing what goes inside. Testing on big ones also tends to look like a giant science experiment, well worth seeing.

 

[mbrooke]

Yes but again you can do things to compensate. More windings gives you a greater flux. You just have to keep the ratio the same. As the total number goes up %Z and copper losses decreases while physical size increases assuming the core is adjusted too.

Switching to copper and/or using more windings to purposely decrease losses is something anyone can do when ordering a transformer to increase efficiency. Just ask to decrease %Z by 1% or so.

If you get the chance it is well worth your time to visit a custom transformer shop or at least a maintenance shop and see for yourself how these things go together. You learn a lot more seeing what goes inside. Testing on big ones also tends to look like a giant science experiment, well worth seeing.

So R goes down but X goes up? I'm confused what it does to the X/R ratio.

 

[paulengr]

So R goes down but X goes up? I'm confused what it does to the X/R ratio.

Yes but only unloaded.

In a transformer we speak of copper and iron losses. It might not be copper or iron but those are the terms. Iron losses are constant regardless of load. And preferably small. It’s what we see unloaded. Copper losses are proportional to load current. Iron losses are inductive (does no work) while copper losses are resistive. But X/R is more a function of the load.