Wye or Star vs the Delta Electrical System

ronaldrc

Senior Member
Location
Tennessee
Hello


I am going to ask one of those off the wall questions I come up with some time that make most on here ignore me.

Here is the Question. Now first I know nothing is 100 percent efficient, but how many on here think that the wye or star electrical system is not 100 percent efficient like the Delta system is?

I look at it this way delta has 3 windings which are completely additive.

With the Three Phase Wye we sacrifice 32 volts just too gain the neutral, that's really a lot of wasted power when you consider how large our electrical systems are.

I do know there are problems with circulating currents with delta to delta but is it really worth the sacrifice?


Would some of you give me your thoughts on this?

Cyber cuts and bruises don't hurt and I couldn't look any worse
so I'm ready for the sticks and stones.

Ronald :)
 

kwired

Electron manager
Location
NE Nebraska
Hello


I am going to ask one of those off the wall questions I come up with some time that make most on here ignore me.

Here is the Question. Now first I know nothing is 100 percent efficient, but how many on here think that the wye or star electrical system is not 100 percent efficient like the Delta system is?

I look at it this way delta has 3 windings which are completely additive.

With the Three Phase Wye we sacrifice 32 volts just too gain the neutral, that's really a lot of wasted power when you consider how large our electrical systems are.

I do know there are problems with circulating currents with delta to delta but is it really worth the sacrifice?


Would some of you give me your thoughts on this?

Cyber cuts and bruises don't hurt and I couldn't look any worse
so I'm ready for the sticks and stones.

Ronald :)
Voltage is 32 volts less, but no power is wasted.

Resistance loads will draw less power but you are still only billed for the power actually used.

Inductive loads will draw more current (if the load remains constant) but again you are only billed for the power actually used.
 

ronaldrc

Senior Member
Location
Tennessee
Voltage is 32 volts less, but no power is wasted.

Resistance loads will draw less power but you are still only billed for the power actually used.

Inductive loads will draw more current (if the load remains constant) but again you are only billed for the power actually used.
I am not thinking in terms of what the customer pays. True lower voltage means less wattage or power.

But in terms of the size of the utilities and generating plants which could be sized smaller if they used those wasted 32 volts.


Ronalds :)
 

kwired

Electron manager
Location
NE Nebraska
I am not thinking in terms of what the customer pays. True lower voltage means less wattage or power.

But in terms of the size of the utilities and generating plants which could be sized smaller if they used those wasted 32 volts.


Ronalds :)
But nothing is lost, meaning for given resistive load power is less but you were still billed for what you used. If you need 10 kWhrs to get the job done it will still take 10 kWhrs, current will just be a little higher or the duration will be longer.
 

GoldDigger

Moderator
Staff member
In terms of the generating plant, nothing is "wasted". The plant just delivers the same energy at a different voltage and current combination.
You need to go back to basic electrical theory.

Sent from my XT1080 using Tapatalk
 

ronaldrc

Senior Member
Location
Tennessee
In terms of the generating plant, nothing is "wasted". The plant just delivers the same energy at a different voltage and current combination.
You need to go back to basic electrical theory.

Sent from my XT1080 using Tapatalk

I think I understand what you are saying but it looks to me like the generating plant had to work harder to produce that 32 volts which did not get used? If we used that extra 32 volts from a delta system it would have produce more power.
 

GoldDigger

Moderator
Staff member
I think I understand what you are saying but it looks to me like the generating plant had to work harder to produce that 32 volts which did not get used? If we used that extra 32 volts from a delta system it would have produce more power.
The plant does not work hard at all to produce volts. It only works to produce volts times amps. Regardless of whether the load is wired wye or delta, the current in each phase wire times the phase to neutral voltage times the phase angle is the power, period.
Wiring the loads to the higher phase to phase voltage allows them to draw a lower current for the same power, allowing them to use less copper. :)
But the power plant cannot tell the difference.

Sent from my XT1080 using Tapatalk
 

kwired

Electron manager
Location
NE Nebraska
I think I understand what you are saying but it looks to me like the generating plant had to work harder to produce that 32 volts which did not get used? If we used that extra 32 volts from a delta system it would have produce more power.
There is no extra 32 volts without a change in current to arrive at the same power. The generating plant can be any voltage, transmission can be any voltage, then we eventually get back to distribution voltage and finally the user service - all transformations are at a ratio. All these transformers change voltage and current changes proportionally so we have same net power on either side of the transformer (disregarding core and line losses).

The transformers with a 240 volt output are just at a different primary to secondary ratio than the ones with a 208 volt output, and either voltage could be wye or delta derived, just so happens the 240 is most commonly from a delta and the 208 most commonly from a wye in North America.
 

Besoeker

Senior Member
Location
UK
Hello


I am going to ask one of those off the wall questions I come up with some time that make most on here ignore me.

Here is the Question. Now first I know nothing is 100 percent efficient, but how many on here think that the wye or star electrical system is not 100 percent efficient like the Delta system is?

I look at it this way delta has 3 windings which are completely additive.

With the Three Phase Wye we sacrifice 32 volts just too gain the neutral, that's really a lot of wasted power when you consider how large our electrical systems are.

I do know there are problems with circulating currents with delta to delta but is it really worth the sacrifice?


Would some of you give me your thoughts on this?

Cyber cuts and bruises don't hurt and I couldn't look any worse
so I'm ready for the sticks and stones.

Ronald :)
And a thought for you that follows the same logic as your wasted 32V.
Many residences in the US are served with 120-0-120.
Lighting is typically run on 120V.
Why not run it on the 240V you get from 120-0-120?
Why waste that 120V?
Do you see where your logic fails?

Product advice:
No sticks and no stones were used in the making of this post.
 

ronaldrc

Senior Member
Location
Tennessee
And a thought for you that follows the same logic as your wasted 32V.
Many residences in the US are served with 120-0-120.
Lighting is typically run on 120V.
Why not run it on the 240V you get from 120-0-120?
Why waste that 120V?
Do you see where your logic fails?

Product advice:
No sticks and no stones were used in the making of this post.
I do understand the Power Law and do agree it throws a wrench in my logic.

But look at it this way our automobiles Electrical systems run on a 12 volt system

But if my circuits are designed so I can just use 9 volts of it why do I want to pay for a battery that requires two more cells to produce that extra 3 volts.

Couldn't the same logic be applied to the size of the Alternators on our electrical system?





And thanks for being easy on me :Ronald :)
 

kwired

Electron manager
Location
NE Nebraska
I do understand the Power Law and do agree it throws a wrench in my logic.

But look at it this way our automobiles Electrical systems run on a 12 volt system

But if my circuits are designed so I can just use 9 volts of it why do I want to pay for a battery that requires two more cells to produce that extra 3 volts.

Couldn't the same logic be applied to the size of the Alternators on our electrical system?





And thanks for being easy on me :Ronald :)
I don't know what typical voltage is for utility generators, and it may depend somewhat on size and other conditions at the generation site. The thing about AC current is it is easily transformed with relatively little loss. In fact commercial distribution is AC because of this. The loss is not 32 volts because we used a wye system instead of a delta though, it is resistance in the lines, losses in the transformers, and is lost as heat.

Lets go back to what you asked in the OP:

Here is the Question. Now first I know nothing is 100 percent efficient, but how many on here think that the wye or star electrical system is not 100 percent efficient like the Delta system is?
...
With the Three Phase Wye we sacrifice 32 volts just too gain the neutral, that's really a lot of wasted power when you consider how large our electrical systems are.

You asked about efficiency. Other than somewhat minimal line and coil loss which you have with either system, power in is equal to power out. So what if it is a different voltage, we can transform to any voltage we want by changing the primary to secondary turn ratio.

You then mention 32 volts as being wasted power. It is not wasted power, it is just voltage that is lower, and to achieve same power current has to go up. There will be additional line losses but it will be fairly minimal.

Compare what you are asking about to why we don't use 480 volts for everything instead of 120, 240 or 208. There will be less line losses in the 480 volt system, but aside from that, power in is still equal to power out. Those line losses can be compensated for by using larger conductors regardless of the voltage and for most basic calculations we disregard those kinds of losses.
 
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ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
I am not thinking in terms of what the customer pays. True lower voltage means less wattage or power.

But in terms of the size of the utilities and generating plants which could be sized smaller if they used those wasted 32 volts.


Ronalds :)
There is no wasted 32 volts. The only thing that is changed is the reference point from which the phase voltage is measured.
 

Besoeker

Senior Member
Location
UK
I do understand the Power Law and do agree it throws a wrench in my logic.

But look at it this way our automobiles Electrical systems run on a 12 volt system

But if my circuits are designed so I can just use 9 volts of it why do I want to pay for a battery that requires two more cells to produce that extra 3 volts.
To have the same capacity, the cells would need to be physically larger. And 9V lights would need more current for the same output light output. So your battery wouldn't be any smaller, the currents would be higher so conductors might have to be beefed up. The alternator would have to be capable of a higher current output. It's a no win.

Couldn't the same logic be applied to the size of the Alternators on our electrical system?
If you need 100kW, you need 100kW regardless of the voltage.
Think about transmission lines. They are high voltage for a reason. It gets the current down for the same power to be transmitted.


And thanks for being easy on me :Ronald :)
You're welcome.
 

ronaldrc

Senior Member
Location
Tennessee
Please disregard my stupid answer. Thank you.

I didn't think it was a stupid question, I did start to ask you what you where referring to though.

I do think the loss of the 32 volts is neg. PF. at the very least.

I just wanted some thought on this 32 volts and I do appreciate the feedback.

Ronald :)
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Engineer
With the Three Phase Wye we sacrifice 32 volts just too gain the neutral, that's really a lot of wasted power when you consider how large our electrical systems are.
Such a sleight of hand, first you mention transformer connections, then you jump to voltage differences.
What "power" do you consider is wasted with:
Delta system at 240V
Wye system at 240Y/138V
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
I didn't think it was a stupid question, I did start to ask you what you where referring to though.

I do think the loss of the 32 volts is neg. PF. at the very least.

I just wanted some thought on this 32 volts and I do appreciate the feedback.

Ronald :)
I was thinking 1.17something for the square root of 3 instead of 1.7something. Brain fart.

But the difference between any two low voltage distribution voltages is just a difference in the windings ratio of a transformer supplying the end user. It doesn't mean that anything is being wasted.
 

gar

Senior Member
131211-1022 EST

ronaldrc:

You need a basic understanding of fundamentals. One fundamental is the "conservation of energy". See http://en.wikipedia.org/wiki/Conservation_of_energy

Start at the thermal engine driving an alternator. Coal or some other fuel is used to provide the input energy to drive a steam engine or turbine. The connected generator or alternator is a load on the heat engine. Whatever, electrical loads are on the generator are indirectly a load on the original source of energy (coal or whatever).

If there is no current being drawn from the generator, then there is no electrical load, but the generator is producing some voltage. There is a load on the original source of energy in the form of friction and other losses in the system. A big part of the loss is in the conversion of heat power into mechanical power. Mostly in that only a portion of the input heat energy is converted to mechnical energy, and the rest is lost heat energy as heat.

If I have an AC generator, and fully electrically load it with high quality capacitors to the point of full rated current, then I have essentially no power load on the generator. But I will have maximum allowed power dissipation in the generator. The internal losses in the generator now require some additional and equal input energy from the heat source.

Next remove the capacitor load. Put a pure resistive load on the generator that draws the maximum rated current. You now have the same internal losses in the generator as with the capacitive load, and additionally the power being dissipated in the load resistor. Now the source of heat energy has to supply all of the load energy.

The only place I mentioned voltage was with reference to the fact that voltage is present without any load current on the generator.

You have already been told by others that you are confusing voltage with power or energy.

On an instantaneous basis power can be described by the equation:

p = v*i and energy is the integral (summation) of p*dt over some time period.

In p*dt p is the instantaneous power and dt is an infinitismal period of time.


Consider your car battery example. Once car batteries were a nominal 6 V. In the 1950s this changed over a few years to 12 V. Why?

First: lead-acid cells have a nominal voltage of 2 V, thus any battery will be made to have a nominal voltage of 2*N where N is an integer. Fewer cells used means fewer components and less assembly cost.

Second: 6 V was adequate to start early engines, and power the limited electrical equipment. Starting in the 1950s engines got bigger and compression ratios increased. This required more torque from the starter motor. Also the electrical load was increasing. Because of higher currents and high resistive losses the decision was made to double the nominal voltage. The loads were designed around the new voltage level. Soon we may go to 24 to 48 V.

The source voltage was determined by an overall determination of system requirements balanced by cost of manufacture. With the source voltage defined, then the load components were designed for that source voltage. Your oddball 9 V device was not designed for direct automotive use. Thus, you have to do a voltage conversion by some means. This can be a series pass regulator (power waste) or by a switching regulator or a motor generator. I have a PE103 dynamotor (dynamo?motor, first known use 1899) that I will sell you. 6 or 12 V input and about 500 V output by memory.

.
 
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