Hello,
So I am making my first Amplifier and I'm in desperate need of help.
Parts that ill be using are -
1. Two x 24V - 5Amp Transformer (230V to 24V)( I have 2 units of this transformer)
Specification
• voltage: 2 x 24V
• current: 1 x 5000mA (5A)
• Taps: 24-0-24 @ 5A & 0-6-12 @ 500ma
LINK - 24V - 5Amp Transformer (230V to 24V) [Heavy Duty] : Online Electronic Components Shop, Price in India : electroncomponents.com - 5Amp Transformer (230V to 24V) [Heavy Duty]
2.Low ESR Dual Rail PSU,4700uf/63volts X 8nos
Specifications
*8 pcs ELNA Power Capacitor 4700uf/63volts
*Ultra fast Rectifier using MUR860
LINK - https://www.eight-audio.com/collect...rail-psu-elna-10-000uf-x-4-200v-20a-rectifier
3. Two x EA - Premium 100watts Mosfet Amplifier IRFP240/IRFP9240 (One for each Channel)
Specs -
Power output @ 4 ohms 100 watts
Class AB
Frequency response 30-20,000 Hz
Total Harmonic Distortion 0.01%
Power supply +/- 35 VDC MAX
Transformer rating 24-0-24 volts AC 150VA per channel
LINK - https://www.eight-audio.com/collect...cts/100watts-hi-end-mosfet-amplifier-eaamsm01
Now here's the thing. I am familiar with wiring the PSU to the two Amps. But I still have doubts on wiring the Trans to the PSU.
My amp needs +/- 35V Max(I was told by the manufacturer that it can handle 30-35v without issues).
The transformers I have are Centre-tap. so the terminals go as 24-0-24 @ 5amp. Now to get a rectified output of +/-35V, How should I wire the PSU to the Trans?
Do i connect only the end terminals to input a total of 48v into the PSU or do i connect the end terminals to the same point and connect the centre tap terminal to the other point so that the two transformer terminals are in parallel with each other.
If anybody could give me a simplified wiring diagram for the transformer to PSU, That would be highly appreciated.
Thanks.
So I am making my first Amplifier and I'm in desperate need of help.
Parts that ill be using are -
1. Two x 24V - 5Amp Transformer (230V to 24V)( I have 2 units of this transformer)
Specification
• voltage: 2 x 24V
• current: 1 x 5000mA (5A)
• Taps: 24-0-24 @ 5A & 0-6-12 @ 500ma
LINK - 24V - 5Amp Transformer (230V to 24V) [Heavy Duty] : Online Electronic Components Shop, Price in India : electroncomponents.com - 5Amp Transformer (230V to 24V) [Heavy Duty]
2.Low ESR Dual Rail PSU,4700uf/63volts X 8nos
Specifications
*8 pcs ELNA Power Capacitor 4700uf/63volts
*Ultra fast Rectifier using MUR860
LINK - https://www.eight-audio.com/collect...rail-psu-elna-10-000uf-x-4-200v-20a-rectifier
3. Two x EA - Premium 100watts Mosfet Amplifier IRFP240/IRFP9240 (One for each Channel)
Specs -
Power output @ 4 ohms 100 watts
Class AB
Frequency response 30-20,000 Hz
Total Harmonic Distortion 0.01%
Power supply +/- 35 VDC MAX
Transformer rating 24-0-24 volts AC 150VA per channel
LINK - https://www.eight-audio.com/collect...cts/100watts-hi-end-mosfet-amplifier-eaamsm01
Now here's the thing. I am familiar with wiring the PSU to the two Amps. But I still have doubts on wiring the Trans to the PSU.
My amp needs +/- 35V Max(I was told by the manufacturer that it can handle 30-35v without issues).
The transformers I have are Centre-tap. so the terminals go as 24-0-24 @ 5amp. Now to get a rectified output of +/-35V, How should I wire the PSU to the Trans?
Do i connect only the end terminals to input a total of 48v into the PSU or do i connect the end terminals to the same point and connect the centre tap terminal to the other point so that the two transformer terminals are in parallel with each other.
If anybody could give me a simplified wiring diagram for the transformer to PSU, That would be highly appreciated.
Thanks.
Subtract the rectifier diode drops at the no load voltage and multiply that by 1.414 (close enough). For the full load voltage subtract the forward drop of the rectifier from the full load voltage and multiply that by 1.414. So your forward rectifier drop might be 1.2 V at light load, and 2.2 V or so at full load. You'll need to look up the rectifier you are using and look at the graph of voltage drop vs current to find those figures out. The transformer should have the no load and full load voltages stated that you need.
The procedure above will get you close enough in the ballpark, you don't need anything else too fancy, although you could use a program called PSUD to figure out your power supply. It's a free download, just Google it. You'll be using a standard bridge rectifier circuit to give you the supplies you need. I'm running around, so I did not have time to carefully read your question as the important bits are easily picked out by a quick scan of your post.
-Chris
The procedure above will get you close enough in the ballpark, you don't need anything else too fancy, although you could use a program called PSUD to figure out your power supply. It's a free download, just Google it. You'll be using a standard bridge rectifier circuit to give you the supplies you need. I'm running around, so I did not have time to carefully read your question as the important bits are easily picked out by a quick scan of your post.
-Chris
Thanks for replying this soon. But what I needed to know was just how to wire the transformer to my PSU board. There are 3 terminals on my transformer(24-0-24) and my PSU has 3 input terminals too(AC+,AC- and GND) I want to know which terminals of my transformer go where on my PSU so that my rectified voltage is 30~35V DC.
The transformer is rated as 230:24Vac
That tells you/us that the output is 24Vac when the input is fed with 230Vac and you have connected a big resistor to the secondary as a resistive load.
Change the loading, or change the input and the output voltage will change.
You have to design to suit that VERY VARIABLE output voltage.
Eg.
mains voltage is 238Vac, transformer regulation is 7%, rated is 230:24Vac & 150VA
the output voltage will be:
Vsec = Vsupply/Vrated * 24 * (1+regulation) = 238/230*24*1.07 = 26.57Vac
Attach a 7.68ohms power resistor to each secondary and the output voltage formula changes to: Vsec = Vsupply/Vrated * 24
Rectify that and feed into a capacitor smoothing circuit and you get a DC voltage across the capacitor
Vdc = Vac * sqrt(2) - Diode drop = 26.57 * 1.4141 - 1Vdrop = 36.6Vdc The Vdrop for a bridge passing very low current is ~1V. When passing a significant current it will drop ~1.2V to 1.4V
But feed into a capacitor input filter and you get a different voltage.
Attach a power amp passing no output current and the PSU voltage changes again.
As I said The output is VERY VARIABLE.
You will need to find out your worst case highest DC voltage so that you can specify the correctly rated capacitors.
Don't use 35V capacitors on a 24Vac transformer.
50Vdc caps will be OK.
40V might just be OK if the regulation is low.
That tells you/us that the output is 24Vac when the input is fed with 230Vac and you have connected a big resistor to the secondary as a resistive load.
Change the loading, or change the input and the output voltage will change.
You have to design to suit that VERY VARIABLE output voltage.
Eg.
mains voltage is 238Vac, transformer regulation is 7%, rated is 230:24Vac & 150VA
the output voltage will be:
Vsec = Vsupply/Vrated * 24 * (1+regulation) = 238/230*24*1.07 = 26.57Vac
Attach a 7.68ohms power resistor to each secondary and the output voltage formula changes to: Vsec = Vsupply/Vrated * 24
Rectify that and feed into a capacitor smoothing circuit and you get a DC voltage across the capacitor
Vdc = Vac * sqrt(2) - Diode drop = 26.57 * 1.4141 - 1Vdrop = 36.6Vdc The Vdrop for a bridge passing very low current is ~1V. When passing a significant current it will drop ~1.2V to 1.4V
But feed into a capacitor input filter and you get a different voltage.
Attach a power amp passing no output current and the PSU voltage changes again.
As I said The output is VERY VARIABLE.
You will need to find out your worst case highest DC voltage so that you can specify the correctly rated capacitors.
Don't use 35V capacitors on a 24Vac transformer.
50Vdc caps will be OK.
40V might just be OK if the regulation is low.
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Hi Andrew,
That is a capacitor input filter. If he begins with the rated no load voltage and corrects for the difference in mains voltage, he will get a value that is very close to what he would measure. No need for the more complicated math.
Hi HarshaaRaja,
Depending on your area, you might want to figure out what the maximum AC voltage would be in your area. Sometimes the mains will be at the highest level in the evening / night as most industrial users shut down. I would expect you could measure what amounts to be the worst case high voltage during that time. Maybe the weekend is higher still. To find the lowest mains voltage you'll see, try measuring the mains in the morning of mid afternoon when industrial production is at it's maximum and highest current draw. Depending on how closely your local electricity company corrects the mains voltages, you might find the situation reversed. Still, you want to see the voltages at times of minimum use and maximum use. Take some random measurements during your normal day. If you leave an analog meter connected to the mains on your bench for a bit, it will be easier to see when you should take an accurate measurement. A power line logging meter is the perfect instrument for this, but I doubt many people might have one of those.
Really, once you get your "ballpark" figures, you can build the thing and then take actual measurements. You may find that some parts of your circuit need to have voltage regulated inside your amplifier in case your minimum to maximum voltage swing is too high. If you need a minimum voltage, you must design for that, then make sure your maximum voltage doesn't exceed your maximum value that you can tolerate. Sometimes you'll have to design for the highest voltage level and make due with the performance loss at your lowest voltage points.
Don't get too wound up over super accurate figures. All you need to have are rough figures and some safety headroom for the high voltage situation. All this is dependent on how well the power in your area is regulated, and maybe how much heavy industry exists in your area. Don't lose sight of the actual requirements for your amplifier, and consider that you will probably move while your amplifier is still in use, look at the stated voltage range your electrical company states is it's normal range. You still should measure your actual values where you are in case they are outside the stated range of voltage.
Good luck on your amplifier build!
-Chris
That is a capacitor input filter. If he begins with the rated no load voltage and corrects for the difference in mains voltage, he will get a value that is very close to what he would measure. No need for the more complicated math.
Hi HarshaaRaja,
Depending on your area, you might want to figure out what the maximum AC voltage would be in your area. Sometimes the mains will be at the highest level in the evening / night as most industrial users shut down. I would expect you could measure what amounts to be the worst case high voltage during that time. Maybe the weekend is higher still. To find the lowest mains voltage you'll see, try measuring the mains in the morning of mid afternoon when industrial production is at it's maximum and highest current draw. Depending on how closely your local electricity company corrects the mains voltages, you might find the situation reversed. Still, you want to see the voltages at times of minimum use and maximum use. Take some random measurements during your normal day. If you leave an analog meter connected to the mains on your bench for a bit, it will be easier to see when you should take an accurate measurement. A power line logging meter is the perfect instrument for this, but I doubt many people might have one of those.
Really, once you get your "ballpark" figures, you can build the thing and then take actual measurements. You may find that some parts of your circuit need to have voltage regulated inside your amplifier in case your minimum to maximum voltage swing is too high. If you need a minimum voltage, you must design for that, then make sure your maximum voltage doesn't exceed your maximum value that you can tolerate. Sometimes you'll have to design for the highest voltage level and make due with the performance loss at your lowest voltage points.
Don't get too wound up over super accurate figures. All you need to have are rough figures and some safety headroom for the high voltage situation. All this is dependent on how well the power in your area is regulated, and maybe how much heavy industry exists in your area. Don't lose sight of the actual requirements for your amplifier, and consider that you will probably move while your amplifier is still in use, look at the stated voltage range your electrical company states is it's normal range. You still should measure your actual values where you are in case they are outside the stated range of voltage.
Good luck on your amplifier build!
-Chris
If he can measure his worst case highest voltage, then he does not need any arthmetic.
But, for that he would need a Variac, or pot luck that his mains happens to be at maximum supply voltage while he takes his measurement.
He needs some arithmetic and how to use that to arrive at a worst case highest voltage.
That allows him to specify his capacitors.
Otherwise it is guesswork.
I do not recommend guesswork for any Mains related attachments.
You as an experienced repair specialist and as a Moderator of this Forum know that !
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Hi Andrew,
I am completely aware of this. If you read that post, I pointed out at what times mains voltages would likely be at their extremes. Yes, there is an element of chance involved with that, but short of logging the mains voltage, it is very likely he will see both the maximum and minimum voltage excursions. Please, try it yourself and see. I also recommended that the OP contact the mains supplier and find out what their limits of regulation are. These figures should be outside of what he can measure, but he will also have taken his own readings to confirm those numbers. Doesn't sound like guesswork to me Andrew. In fact, I have had successfully determined my own mains voltage range by that method. For my new bench that is under construction right now, I plan to have the mains continuously monitored and displayed with a dedicated instrument that I will also calibrate. I'm following my own advice.
I think I have been both thorough and mindful in describing how to best capture the highs and lows of your mains voltage variations if a data logger is not available. Some DVMs these days do allow for capturing the minimum, maximum and average of some quantity. I might actually try this to see if there is any major departure from what I believe those limits are. You should give that a whirl Andrew.
Best, Chris
I am completely aware of this. If you read that post, I pointed out at what times mains voltages would likely be at their extremes. Yes, there is an element of chance involved with that, but short of logging the mains voltage, it is very likely he will see both the maximum and minimum voltage excursions. Please, try it yourself and see. I also recommended that the OP contact the mains supplier and find out what their limits of regulation are. These figures should be outside of what he can measure, but he will also have taken his own readings to confirm those numbers. Doesn't sound like guesswork to me Andrew. In fact, I have had successfully determined my own mains voltage range by that method. For my new bench that is under construction right now, I plan to have the mains continuously monitored and displayed with a dedicated instrument that I will also calibrate. I'm following my own advice.
Andrew, I always suggest people use a variac. However, a variac will not help the OP at all in determining his mains voltage swings unless it has in input voltage monitor. Otherwise the main purpose of a variac is to manually regulate the voltage being fed into a piece of equipment. I have three of these and some extra bare variacs as well. They will go into equipment planned for construction.
I think I have been both thorough and mindful in describing how to best capture the highs and lows of your mains voltage variations if a data logger is not available. Some DVMs these days do allow for capturing the minimum, maximum and average of some quantity. I might actually try this to see if there is any major departure from what I believe those limits are. You should give that a whirl Andrew.
Best, Chris
I wish I could, but I don't have any equipment that can do this for me.
As I reported a while back, Scottish Power did monitor my power quality twice when I complained that my voltage was outside the regulated limits.
Their equipment and safety procedure was impressive.
To cure the power quality issue they quadrupled the size of the local 6kV:240Vac transformer to feed our hamlet.
I have and luck never allowed me to measure the 216Vac to 253Vac regulated limits for our "Harmonised" supply voltage.
I regularly see 239Vac to 246Vac but no where near the extremes they are allowed to supply.
Our old standard voltage range before "harmonisation" was 226 to 254Vac, i.e. 240±~6%.
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