output from transformer is coming not as expected

[VickySalunkhe]

Last two images

Query still remains the same
Despite of bulding psu for giving output of 10A or 7A( because of losses)
I am still getting 3.5A max which is still half than what i am expecting.

[Zero999]

My bet is poor wiring. The solder joints are not wetted properly and twisting wires together like that doesn't ensure a good electrical connection!

[Damianos]

Bad wiring, that's for sure.
As mentioned all the solder joints need "repair", also the twisted wires need soldering, especially the connections of the rectifiers.
By the way, are the mains' connections well made and safe? It looks like there are bare feet there!

Some more notes:
- if the rectifiers are all the same, they are 35A/1000V, that is good enough. But this seems that is the only one good thing here!
- if the capacitors are all the same, some of them are abused! On one of them it is written 50V![Edit: it seems that I have confused the numbers! These capacitors have enough voltage margin.]
- the transformers have all the same dimensions, but two of them are 60VA and the others are 120VA, this is not possible!

The refereed AC values are not related with something else, at least they don't seem as ripple voltages. Where are they measured? Maybe the instrument has a strange behavior when it has AC over DC at its input(?).

[VickySalunkhe]

- if the capacitors are all the same, some of them are abused! On one of them it is written 50V!
- the transformers have all the same dimensions, but two of them are 60VA and the others are 120VA, this is not possible!

I have made the connections to the transformer as such to get
Around 38V from two transformers
Around 14V from remaining two transformers
I have total 4 transformer
3 of them are center tapped transformer 12-0-12V 5amp
4th transformer is 0-12V 5amp
Out of 3 center tapped transformer one transformer wiring had been done (wire 1,2 connected) so as to get 14V to match up with 4th transformer



And I tried to solder the wire with the rectifier but the solder wire is not getting stuck woth rectifier metal points.

[Ian.M]

What soldering iron are you using?

If the iron isn't up to the job, you'd be better off connecting the rectifiers with female spade crimp terminals, and joining the wires with screw terminals - either with ring crimp terminals secured by the terminal screw, no more that three ring terminals per screw, or by screw 'choc' block terminals with no more than two wires per side per hole.

[VickySalunkhe]

Will replacing the copper wire used for connections
With metal wire solve the issue of bad wiring?
Single Metal wire of thick width of about 2mm?
Will that work?

[Brumby]

Will replacing the copper wire used for connections
With metal wire solve the issue of bad wiring?
Single Metal wire of thick width of about 2mm?
Will that work?

Don't bother with that.  The copper wire used here should be more than good enough to solve your major problems.  Whether you need to go any thicker is a question for later.

When the phrase "bad wiring" is used here, we are talking about how well the terminations have been done.  In short - your connections are poor.

If we were to criticise the actual wire you have used, we would have said things like "poor quality wire", "inadequate" or things like that.

[Brumby]

I have strong doubt about the center tap transformer
i think i have read somewhere
by connecting wire 1 and 3 we get half the rated current is that true ?

No.

Only the voltage of a centre-tapped secondary is different, depending on which connections you use.  The current rating will be the same for any combination.

[Brumby]

5. Can you test the supply as suggested showing:
    a) DC volts, AC volts - with no load  and..

Transformer / Circuit	DC VOLTAGE	AC VOLTAGE
Full Circuit	58.6V	128.6V
1 & 2 (IN SERIES)	58.2V	127.6V
3 & 4 (IN SERIES)	58V	127.6V
transformer 1	39.2V	85.7V
transformer 2	19.2V	41.8V
transformer 3	39.4V	86V
transformer 4	18.93V	40.8V

    b) DC volts, AC volts, DC amps - for a load current between 0.5a and, say, 3A

Full Circuit	1 & 2 (IN SERIES)	3 & 4 (IN SERIES)
56.8VDC      125VAC     0.05 A	56.1VDC      123.2VAC     0.05 A	55.8VDC      122.9VAC     0.05 A
46.5VDC      99VAC     1.5 A	49.1VDC      108.2VAC     0.5 A	49.8VDC      109.3VAC     0.5 A
43.5VDC      95VAC     2 A	43.5VDC      96.2VAC     1 A	44.6VDC      98.1VAC     1 A
37VDC      81VAC     3.4 A(MAX)	42VDC      92VAC     1.16 A(MAX)	43VDC      94.3VAC     1.17 A(MAX)

Readings for full circuit are not accurate as i was not able to take readings on specific current value as i have taken for half circuit

Those AC volts readings are bizarre.

[Damianos]

- if the capacitors are all the same, some of them are abused! On one of them it is written 50V!
- the transformers have all the same dimensions, but two of them are 60VA and the others are 120VA, this is not possible!

I have made the connections to the transformer as such to get
Around 38V from two transformers
Around 14V from remaining two transformers
I have total 4 transformer
3 of them are center tapped transformer 12-0-12V 5amp
4th transformer is 0-12V 5amp
Out of 3 center tapped transformer one transformer wiring had been done (wire 1,2 connected) so as to get 14V to match up with 4th transformer



And I tried to solder the wire with the rectifier but the solder wire is not getting stuck woth rectifier metal points.

I was wrong! The voltage rating of the capacitors looks good enough.

The power of the transformers that you have are 12V*5A=60VA and 24V*5A=120VA, but they have the same dimensions.

[Brumby]

The power of the transformers that you have are 12V*5A=60VA and 24V*5A=120VA, but they have the same dimensions.

My guess is that the manufacturer got a great deal on E-I cores and made up a couple of variants with different secondaries.  (There's less copper in the 60VA versions.)

[Brumby]

5. Can you test the supply as suggested showing:
    a) DC volts, AC volts - with no load  and..

Transformer / Circuit	DC VOLTAGE	AC VOLTAGE
Full Circuit	58.6V	128.6V
1 & 2 (IN SERIES)	58.2V	127.6V
3 & 4 (IN SERIES)	58V	127.6V
transformer 1	39.2V	85.7V
transformer 2	19.2V	41.8V
transformer 3	39.4V	86V
transformer 4	18.93V	40.8V

    b) DC volts, AC volts, DC amps - for a load current between 0.5a and, say, 3A

Full Circuit	1 & 2 (IN SERIES)	3 & 4 (IN SERIES)
56.8VDC      125VAC     0.05 A	56.1VDC      123.2VAC     0.05 A	55.8VDC      122.9VAC     0.05 A
46.5VDC      99VAC     1.5 A	49.1VDC      108.2VAC     0.5 A	49.8VDC      109.3VAC     0.5 A
43.5VDC      95VAC     2 A	43.5VDC      96.2VAC     1 A	44.6VDC      98.1VAC     1 A
37VDC      81VAC     3.4 A(MAX)	42VDC      92VAC     1.16 A(MAX)	43VDC      94.3VAC     1.17 A(MAX)

Readings for full circuit are not accurate as i was not able to take readings on specific current value as i have taken for half circuit

Those AC volts readings are bizarre.

Not only are those AC voltage readings way too high, but they should be increasing with greater load, not decreasing.

These AC voltage readings should have been made across the capacitors - exactly the same points as the DC voltages.  Is that where they were made?

[VickySalunkhe]

These AC voltage readings should have been made across the capacitors - exactly the same points as the DC voltages.  Is that where they were made?

YES

[Brumby]

This may sound like a strange request - but repeat just one of those AC voltage measurements and then swap the meter leads and measure it again...

Does the meter give you the same reading?

[VickySalunkhe]

This may sound like a strange request - but repeat just one of those AC voltage measurements and then swap the meter leads and measure it again...

Does the meter give you the same reading?

NO

While testing the AC voltages swapping the meter leads gave output of 0V for all combinations

[Brumby]

Now I am officially confused.

How come we have gone from AC measurements ranging from 40V to 126V - to 0V?

[Damianos]

The power of the transformers that you have are 12V*5A=60VA and 24V*5A=120VA, but they have the same dimensions.

My guess is that the manufacturer got a great deal on E-I cores and made up a couple of variants with different secondaries.  (There's less copper in the 60VA versions.)

Maybe it is more cost effective for them to use the same cores and bobbins (?).

[VickySalunkhe]

Sir
I am testing a dc voltage by setting the dial on ac
So it must give high voltage on one side and 0 voltage on other side right

Am i right?
Or
You are asking something different which i have not got yet

[Damianos]

Obviously the instrument has not an AC coupling, so it shows strange results. It is seemed that it uses half wave rectification...
If there is a capacitor available, of more than 1 micro Farad, putting it in series with the instrument will give an indication of the ripple. This has to be zero without load and increasing with the output current.

[Brumby]

Obviously the instrument has not an AC coupling, so it shows strange results. It is seemed that it uses half wave rectification...

That is not obvious - but it is a possibility.

What is obvious is that we have some measurement issues.

If there is a capacitor available, of more than 1 micro Farad, putting it in series with the instrument will give an indication of the ripple. This has to be zero without load and increasing with the output current.

This is an idea - but the capacitor must be allowed to charge up to match the DC offset.

[Damianos]

Obviously the instrument has not an AC coupling, so it shows strange results. It is seemed that it uses half wave rectification...

That is not obvious - but it is a possibility.

What is obvious is that we have some measurement issues.

How do you explain this:

This may sound like a strange request - but repeat just one of those AC voltage measurements and then swap the meter leads and measure it again...

Does the meter give you the same reading?

NO

While testing the AC voltages swapping the meter leads gave output of 0V for all combinations

... if it is AC coupled?

If there is a capacitor available, of more than 1 micro Farad, putting it in series with the instrument will give an indication of the ripple. This has to be zero without load and increasing with the output current.

This is an idea - but the capacitor must be allowed to charge up to match the DC offset.

What prohibits the capacitor to charge up?

[VickySalunkhe]

How do you explain this:

This may sound like a strange request - but repeat just one of those AC voltage measurements and then swap the meter leads and measure it again...

Does the meter give you the same reading?

NO

While testing the AC voltages swapping the meter leads gave output of 0V for all combinations

... if it is AC coupled?

Sir as i am using full wave rectifier to convert ac to dc
One side will be double of the orginal amplitude
So acc. To that other side will have 0 V

So that's what i am getting
While i am getting some reading when i swap the meter leads of multimeter to the connection
It shows 0V and it should right?

[Damianos]

I can not understand the meaning of your description. Where do you mean there is a double voltage?
What are you measuring? Can you show this on a diagram?

[Brumby]

Obviously the instrument has not an AC coupling, so it shows strange results. It is seemed that it uses half wave rectification...

That is not obvious - but it is a possibility.

What is obvious is that we have some measurement issues.

How do you explain this:

This may sound like a strange request - but repeat just one of those AC voltage measurements and then swap the meter leads and measure it again...

Does the meter give you the same reading?

NO

While testing the AC voltages swapping the meter leads gave output of 0V for all combinations

... if it is AC coupled?

The OP isn't measuring what you think they are measuring.  This is borne out by this post of yours...

I can not understand the meaning of your description. Where do you mean there is a double voltage?
What are you measuring? Can you show this on a diagram?

... and this is something that I have been wanting to see for some time.  I have an answer in the pipeline...

If there is a capacitor available, of more than 1 micro Farad, putting it in series with the instrument will give an indication of the ripple. This has to be zero without load and increasing with the output current.

This is an idea - but the capacitor must be allowed to charge up to match the DC offset.

What prohibits the capacitor to charge up?

The impedance of the multimeter and time.  With a fully discharged 1uF cap and a 10M DMM input impedance, it will take around a minute for it to charge within 10% of the supply voltage and close to 2 minutes to get within 1%.  If there are any DC offset issues with the meter, then the DC component of the measurement setup needs to be zero.  There is a way to speed this up, though.  Simply charge the capacitor directly off the supply first.  One more consideration - that the capacitor have low leakage, otherwise the DC current flow could cause problems.

[Gregg]

Sometimes it is better to just start over.  By that I mean take it all apart and put it back together one part at a time making sure all connections are really good.  Test each part before connecting it to another and then test in circuit at each logical step of the assembly process.  Labeling the wires may help to test further as you assemble each power supply. 
1.   Take one transformer and test the input AC voltage and output voltage no load.  Make sure the output is what you expect and for the dual winding ones this will ensure they two aren’t cancelling each other.
2.   If possible put a load on the transformer output and measure the voltage again both in and out.  Write down the results
3.   Next add a bridge rectifier and test again both open circuit and with a load for AC volts on the input of the rectifier and DC volts on the output terminals
4.   I would leave the capacitors out until near the final testing
5.   After you have assembled the two higher voltage systems, try paralleling them and take some more readings.  If they are what you expect try them on the motor control and see what happens.
6.   Continue piece by piece in an orderly fashion until it either works or you see something that isn’t right.
7.   Post the results.

This is how you learn, by making mistakes and figuring them out; lessons you won’t forget.

( It is quite rare to officially confuse Brumby )