loss of phase... what if question

[Smart $]

But there would be no 120deg separation, right?

Correct.

 

[winnie]

But there would be no 120deg separation, right?

No 120 degree phase separation...unless you got very lucky.

With one primary leg lost, only single phase power will be supplied to the transformer.

With balanced resistive loads on the secondary (as was specified) all of the secondary voltages will be essentially in phase.

With the right combination of secondary loads, I would bet that you _could_ get a 120 degree phase separation, but that is essentially using the energy stored magnetically in the transformer to provide phase conversion. It wouldn't be a useful technique for generating proper phase angles, but I guess a measured phase angle difference on the secondary side could not rule out loss of phase on the primary side.

-Jon

 

[Electric-Light]

No 120 degree phase separation...unless you got very lucky.

With one primary leg lost, only single phase power will be supplied to the transformer.

With balanced resistive loads on the secondary (as was specified) all of the secondary voltages will be essentially in phase.

With the right combination of secondary loads, I would bet that you _could_ get a 120 degree phase separation, but that is essentially using the energy stored magnetically in the transformer to provide phase conversion. It wouldn't be a useful technique for generating proper phase angles, but I guess a measured phase angle difference on the secondary side could not rule out loss of phase on the primary side.

-Jon

If you put a three phase motor on the secondary and capacitor start it, then I'm sure you'll end up with tree phaise pwr

 

[winnie]

If you put a three phase motor on the secondary and capacitor start it, then I'm sure you'll end up with tree phaise pwr

Agreed, although you would probably get better results putting it in parallel with the primary

-Jon

 

[mivey]

Actually, I had to recheck mine, too, and I see where I made a mistake! Your magnitudes are good but three angles are off.

AN = 60<-90d
BN = 60<-90d
CN = 120<90d
AB = 0
BC = 180<90d
CA = 180<-90d

Nope. Only one. It should have been:

the secondaries become:
AN = 60<-90d
BN = 60<-90d
CN = 120<90d
AB = 0
BC = 180<-90d
CA = 180<90d

Add: before the phase loss we have:
AN = 120<-30d
BN = 120<-150d
CN = 120<90d
AB = 208<0d
BC = 208<-120d
CA = 208<120d

 

[mivey]

ah, good, someone finally agrees with my answer <G>?

Yes.

 

[Smart $]

Nope. Only one. It should have been:

the secondaries become:
AN = 60<-90d
BN = 60<-90d
CN = 120<90d
AB = 0
BC = 180<-90d
CA = 180<90d

Add: before the phase loss we have:
AN = 120<-30d
BN = 120<-150d
CN = 120<90d
AB = 208<0d
BC = 208<-120d
CA = 208<120d

Let's just say we were both wrong... twice. When I figured it the first time, I made a mistake, which I discovered the second time. Then the second time, I was trying to convert my angles based on primary ?A vector being 0deg, to your secondary AN being 0deg. Now, on you last post you changed your secondary AN is -30deg before loss!!! Anyway,I think I have it completely sorted.

With voltages based on "an" before loss as being the 0deg reference, after loss of primary Line A we have:

an = 60<-60d
bn = 60<-60d
cn = 120<120d
ab = 0
bc = 180<-60d
ca = 180<120d

 

[mivey]

Let's just say we were both wrong... twice.

I'll agree you were wrong twice. My one mistake was dropping the minus sign for the AN angle on the secondary in my original post. I was half asleep. All of the other voltages and angles I posted were correct.

When I figured it the first time, I made a mistake, which I discovered the second time. Then the second time, I was trying to convert my angles based on primary ?A vector being 0deg, to your secondary AN being 0deg.

I gave the primary and secondary voltages as they would flow through a normal D-Y transformer. No need to reset the secondary angle to zero. The part that was of interest after all was the voltage and angle relationships.

Now, on you last post you changed your secondary AN is -30deg before loss!!!

That never changed. Check my original post and primary voltages and angles and it will be clear.

Anyway,I think I have it completely sorted.

With voltages based on "an" before loss as being the 0deg reference, after loss of primary Line A we have:

an = 60<-60d
bn = 60<-60d
cn = 120<120d
ab = 0
bc = 180<-60d
ca = 180<120d

Quite right for that scenario, but not my original voltage arrangement. My arrangement started with the source having a zero AN angle. With your scenario of finishing with a zero AN angle we have:

With primary supply of
AN = 277<30d
BN = 277<-90d
CN = 277<150d
AB = 480<60d
BC = 480<-60d
CA = 480<180d

and before the phase loss we have these secondaries:
AN = 120<0d
BN = 120<-120d
CN = 120<120d
AB = 208<30d
BC = 208<-90d
CA = 208<150d

then losing supply A so we get the following at the primary windings:

AC = 240<-60d
BA = 240<-60d
CB = 480<120d

the secondaries become:
AN = 60<-60d
BN = 60<-60d
CN = 120<120d
AB = 0
BC = 180<-60d
CA = 180<120d

Hopefully no typos on that one.

 

[Smart $]

...

I gave the primary and secondary voltages as they would flow through a normal D-Y transformer. No need to reset the secondary angle to zero. The part that was of interest after all was the voltage and angle relationships.

...

True... but you're the only one saying the primary system is wye (or virtual wye).

 

[mivey]

True... but you're the only one saying the primary system is wye (or virtual wye).

The primary neutral reference voltages were given to show the shift from primary to secondary. The transformer primary is 3-wire delta so it is the same as phase-ground references. Note that I dropped the primary phase-neutral voltages after the lost phase because there is a neutral shift and they would not have added value.

 

[Smart $]

The primary neutral reference voltages were given to show the shift from primary to secondary. The transformer primary is 3-wire delta so it is the same as phase-ground references. Note that I dropped the primary phase-neutral voltages after the lost phase because there is a neutral shift and they would not have added value.

I don't care what your reason(s) were or are, secondary wye voltages are, in general, referenced by nominal "an" voltage as 0 degrees... and that corresponds to the primary "AC" voltage. There is no need for primary "AN", real or virtual, to enter the picture on a D-Y xfmer issue.

 

[mivey]

I don't care what your reason(s) were or are

No matter. I made the calculations I considered interesting. You are free to do likewise.

secondary wye voltages are, in general, referenced by nominal "an" voltage as 0 degrees... and that corresponds to the primary "AC" voltage.

If the secondary voltages stand alone maybe. If looking at source and load side, generally we take a voltage reference from the source and progress towards the load. YMMV.

There is no need for primary "AN", real or virtual, to enter the picture on a D-Y xfmer issue.

I find it useful at times. Transformer phase relation diagrams do this as well.

 

[Smart $]

No matter. I made the calculations I considered interesting. You are free to do likewise.

As you know, we are free to do it any way we like... but that don't mean I have to like yours... LOL

If the secondary voltages stand alone maybe. If looking at source and load side, generally we take a voltage reference from the source and progress towards the load. YMMV.

That "we" is far from all inclusive. YMWNV.

I find it useful at times. Transformer phase relation diagrams do this as well.

As stated, you are free to do it anyway you like... and I actually recommend doing it that way if it is useful to you. However, I have yet to see a transformer diagram which actually uses it. Most will show PRI AC or H1-H3 and SEC AN at 180 degrees, and many to most show a virtual PRI AN at -150 degrees.

 

[mivey]

As you know, we are free to do it any way we like... but that don't mean I have to like yours... LOL

And risk hurting my feelings?

That "we" is far from all inclusive.

Of course there are times it is useful the other way. My comment was in general practice, standards and otherwise when we relate the primary and secondary sides.

However, I have yet to see a transformer diagram which actually uses it.

Keep Googling. You will find it is the way the phase shift is referenced for different configurations.

Most will show PRI AC or H1-H3 and SEC AN at 180 degrees, and many to most show a virtual PRI AN at -150 degrees.

I see you did learn that AN does enter the picture. Keep searching. Look up the way phase relationships are designated.

 

[Electric-Light]

I gave the primary and secondary voltages as they would flow through a normal D-Y transformer. No need to reset the secondary angle to zero. The part that was of interest after all was the voltage and angle relationships.

You attach two synchronous alternators like this on a doubled ended motor. You bring them into phase by adjusting mechanically so the two are perfectly in phase...

If you parallel them through a 1:1 transformer would it bind or let out the smoke?

 

[GoldDigger]

You attach two synchronous alternators like this on a doubled ended motor. You bring them into phase by adjusting mechanically so the two are perfectly in phase...

If you parallel them through a 1:1 transformer would it bind or let out the smoke?

As long as you oriented the lead polarity of the 1:1 transformer correctly, the two should parallel just fine with only load current to let out the smoke.
The motor will be driving twice the mechanical load of one alternator if you load each alternator to full output.
Just make sure that you do not try to connect your transformer after a rectifier bridge!!

 

[junkhound]

You attach two synchronous alternators like this on a doubled ended motor. You bring them into phase by adjusting mechanically so the two are perfectly in phase...

If you parallel them through a 1:1 transformer would it bind or let out the smoke?

There will be serious balance problems with the left generator AND the motor. You will need to re-align the shafts to keep the whole thing from shaking apart.

 

[Phil Corso]

Electric Light...

Although they will operate at the same frequency, their output voltages will not be "aligned" unless physically done so! This fact is also true even though the are connected via a 1:1 Xfmr.

For more info I suggest searching the WEB for "Tandem-coupled Induction-motors"!

Regards, Phil Corso

 

[winnie]

You would need to be careful about the phase rotation; one will be spinning clockwise and the other counterclockwise. Which means that you can't simply connect (directly or via a transformer) phase A to A, B to B and C to C. You would need to adjust the phase angle, and swap a pair of phases. But if everything is aligned, excitation adjusted, etc., then you should be able to parallel the two alternators.

-Jon

 

[Smart $]

...

Keep Googling. You will find it is the way the phase shift is referenced for different configurations.

I see you did learn that AN does enter the picture. Keep searching. Look up the way phase relationships are designated.

I don't have to look it up. I already know how phase angle displacements are depicted.