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C
Commander Kinsey
Guest
On Tue, 04 Apr 2023 04:04:47 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
They get damn hot. What else would limit it?
On Mon, 03 Apr 2023 22:12:31 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Mon, 27 Mar 2023 18:55:25 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
On Mon, 27 Mar 2023 17:55:51 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Commander Kinsey <CK1@nospam.com> wrote:
I have a centre tapped transformer I wanted to get the most power out of.
Thinking a traditional full wave rectifier (just a diode on each side,
calling the centre tap 0V at the output) is only running current through
one half of the secondary at a time, which is inefficient (think of
P=i^2R), I thought about putting a bridge rectifier on each half, then
connecting the result in parallel. I made the following diagram by
adjusting someone else\'s, so it may look a bit odd.
https://i.imgur.com/d2TfZYO.jpg
I\'m a bit confused here because you can trace the current flow and show
the output has both 24V (if the current goes through the \"wrong\" bridge on
the way back) and 12V at the same time, which isn\'t possible. Can someone
explain what would happen in this circuit?
Any way to make this work? I want current flowing through both halves of
the secondary all the time. But I want half the full secondary\'s voltage.
There is nothing you can do to increase the power if your load is
resistive - but if it is smoothed with a capacitor, there might be.
Using a choke between the rectifiers and the first smoothing capacitor
will even-out the current peaks through the transformer windings and
reduce the losses which are proportional to the square of the current.
You may then be able to run the transformer at a higher current than the
\'official\' rating, which is usually specified for peaky rectified
current.
The output voltage will then be approximately the RMS voltage of the
waveform
Average is 2/pi times peak, which is a bit less.
(minus diode drops, the transformer winding resistance losses
and the choke resistance losses), not the rectified peak voltage. (minus
diode drops and somewhat larger transformer winding resistance loses).
Whether this ultimately equates to more *power*, rather than just more
current, will depend on the parameters of transformer and choke.
Another way to increse the power handling of an particlar size of
transformer is to increase the frequency. This may not be practical for
a mains transformer - and you will soon run into greater losses from
eddy currents in the core at higher frequencies - but it is commonly
used to reduce the size and weight of transformers in aircraft.
Power handling of a transformer or resistor or inductor improves with
air flow or heat sinking. They are usually specified in still air.
Good idea, I shall add those accordingly, got loads of heatsinks and fans kicking about.
Can I do the same with a SMPS? Mind you they\'re probably limited so I\'d need to alter the circuit.
Yes, air flow increases the power capability of most things. Resistors
can be run at 1.5 to as much as 5x rated power with a lot of air. This
is usually best determined by testing.
A flyback power supply may never put out much more than design
power... probably not cooling limited.
They get damn hot. What else would limit it?
J
John Larkin
Guest
On Thu, 13 Apr 2023 16:12:17 +0100, \"Commander Kinsey\"
<CK1@nospam.com> wrote:
Energy stored in the inductor times the pulse rate is the limit of
output power, and both are usually limited.
Cooling will improve reliability if it\'s getting hot.
<CK1@nospam.com> wrote:
On Tue, 04 Apr 2023 04:04:47 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
On Mon, 03 Apr 2023 22:12:31 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Mon, 27 Mar 2023 18:55:25 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
On Mon, 27 Mar 2023 17:55:51 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Commander Kinsey <CK1@nospam.com> wrote:
I have a centre tapped transformer I wanted to get the most power out of.
Thinking a traditional full wave rectifier (just a diode on each side,
calling the centre tap 0V at the output) is only running current through
one half of the secondary at a time, which is inefficient (think of
P=i^2R), I thought about putting a bridge rectifier on each half, then
connecting the result in parallel. I made the following diagram by
adjusting someone else\'s, so it may look a bit odd.
https://i.imgur.com/d2TfZYO.jpg
I\'m a bit confused here because you can trace the current flow and show
the output has both 24V (if the current goes through the \"wrong\" bridge on
the way back) and 12V at the same time, which isn\'t possible. Can someone
explain what would happen in this circuit?
Any way to make this work? I want current flowing through both halves of
the secondary all the time. But I want half the full secondary\'s voltage.
There is nothing you can do to increase the power if your load is
resistive - but if it is smoothed with a capacitor, there might be.
Using a choke between the rectifiers and the first smoothing capacitor
will even-out the current peaks through the transformer windings and
reduce the losses which are proportional to the square of the current.
You may then be able to run the transformer at a higher current than the
\'official\' rating, which is usually specified for peaky rectified
current.
The output voltage will then be approximately the RMS voltage of the
waveform
Average is 2/pi times peak, which is a bit less.
(minus diode drops, the transformer winding resistance losses
and the choke resistance losses), not the rectified peak voltage. (minus
diode drops and somewhat larger transformer winding resistance loses).
Whether this ultimately equates to more *power*, rather than just more
current, will depend on the parameters of transformer and choke.
Another way to increse the power handling of an particlar size of
transformer is to increase the frequency. This may not be practical for
a mains transformer - and you will soon run into greater losses from
eddy currents in the core at higher frequencies - but it is commonly
used to reduce the size and weight of transformers in aircraft.
Power handling of a transformer or resistor or inductor improves with
air flow or heat sinking. They are usually specified in still air.
Good idea, I shall add those accordingly, got loads of heatsinks and fans kicking about.
Can I do the same with a SMPS? Mind you they\'re probably limited so I\'d need to alter the circuit.
Yes, air flow increases the power capability of most things. Resistors
can be run at 1.5 to as much as 5x rated power with a lot of air. This
is usually best determined by testing.
A flyback power supply may never put out much more than design
power... probably not cooling limited.
They get damn hot. What else would limit it?
Energy stored in the inductor times the pulse rate is the limit of
output power, and both are usually limited.
Cooling will improve reliability if it\'s getting hot.
C
Commander Kinsey
Guest
On Thu, 13 Apr 2023 18:44:47 +0100, John Larkin <jjlarkin@highlandtechnology.com> wrote:
One of them (12V 83A) smells bad at only 60A. But it\'s been running 24/7 like that for a couple of years.
Another (12V 40A) gave up after running at half power for 4 months. When I opened it I found the two largest transistors weren\'t tightly attached to the heatsink, and were dead shorts across all three pins. Would that have killed anything else in the circuit? I\'ve ordered two replacement transistors (J13009). To be fair, it used to power a scuba compressor (at 40A) which made a lot of vibration.
On Thu, 13 Apr 2023 16:12:17 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Tue, 04 Apr 2023 04:04:47 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
On Mon, 03 Apr 2023 22:12:31 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Mon, 27 Mar 2023 18:55:25 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
On Mon, 27 Mar 2023 17:55:51 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Commander Kinsey <CK1@nospam.com> wrote:
I have a centre tapped transformer I wanted to get the most power out of.
Thinking a traditional full wave rectifier (just a diode on each side,
calling the centre tap 0V at the output) is only running current through
one half of the secondary at a time, which is inefficient (think of
P=i^2R), I thought about putting a bridge rectifier on each half, then
connecting the result in parallel. I made the following diagram by
adjusting someone else\'s, so it may look a bit odd.
https://i.imgur.com/d2TfZYO.jpg
I\'m a bit confused here because you can trace the current flow and show
the output has both 24V (if the current goes through the \"wrong\" bridge on
the way back) and 12V at the same time, which isn\'t possible. Can someone
explain what would happen in this circuit?
Any way to make this work? I want current flowing through both halves of
the secondary all the time. But I want half the full secondary\'s voltage.
There is nothing you can do to increase the power if your load is
resistive - but if it is smoothed with a capacitor, there might be.
Using a choke between the rectifiers and the first smoothing capacitor
will even-out the current peaks through the transformer windings and
reduce the losses which are proportional to the square of the current.
You may then be able to run the transformer at a higher current than the
\'official\' rating, which is usually specified for peaky rectified
current.
The output voltage will then be approximately the RMS voltage of the
waveform
Average is 2/pi times peak, which is a bit less.
(minus diode drops, the transformer winding resistance losses
and the choke resistance losses), not the rectified peak voltage. (minus
diode drops and somewhat larger transformer winding resistance loses).
Whether this ultimately equates to more *power*, rather than just more
current, will depend on the parameters of transformer and choke.
Another way to increse the power handling of an particlar size of
transformer is to increase the frequency. This may not be practical for
a mains transformer - and you will soon run into greater losses from
eddy currents in the core at higher frequencies - but it is commonly
used to reduce the size and weight of transformers in aircraft.
Power handling of a transformer or resistor or inductor improves with
air flow or heat sinking. They are usually specified in still air.
Good idea, I shall add those accordingly, got loads of heatsinks and fans kicking about.
Can I do the same with a SMPS? Mind you they\'re probably limited so I\'d need to alter the circuit.
Yes, air flow increases the power capability of most things. Resistors
can be run at 1.5 to as much as 5x rated power with a lot of air. This
is usually best determined by testing.
A flyback power supply may never put out much more than design
power... probably not cooling limited.
They get damn hot. What else would limit it?
Energy stored in the inductor times the pulse rate is the limit of
output power, and both are usually limited.
Cooling will improve reliability if it\'s getting hot.
One of them (12V 83A) smells bad at only 60A. But it\'s been running 24/7 like that for a couple of years.
Another (12V 40A) gave up after running at half power for 4 months. When I opened it I found the two largest transistors weren\'t tightly attached to the heatsink, and were dead shorts across all three pins. Would that have killed anything else in the circuit? I\'ve ordered two replacement transistors (J13009). To be fair, it used to power a scuba compressor (at 40A) which made a lot of vibration.
J
John Larkin
Guest
On Fri, 14 Apr 2023 14:54:11 +0100, \"Commander Kinsey\"
<CK1@nospam.com> wrote:
Unlikely to be a flyback, at that power.
Bad heat sinking for sure.
Heat skinks are expensive so that\'s where people skrimp. More air will
certainly make power supplies more reliable.
Vibration may have loosened the screws on the transistors.
<CK1@nospam.com> wrote:
On Thu, 13 Apr 2023 18:44:47 +0100, John Larkin <jjlarkin@highlandtechnology.com> wrote:
On Thu, 13 Apr 2023 16:12:17 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Tue, 04 Apr 2023 04:04:47 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
On Mon, 03 Apr 2023 22:12:31 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Mon, 27 Mar 2023 18:55:25 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
On Mon, 27 Mar 2023 17:55:51 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Commander Kinsey <CK1@nospam.com> wrote:
I have a centre tapped transformer I wanted to get the most power out of.
Thinking a traditional full wave rectifier (just a diode on each side,
calling the centre tap 0V at the output) is only running current through
one half of the secondary at a time, which is inefficient (think of
P=i^2R), I thought about putting a bridge rectifier on each half, then
connecting the result in parallel. I made the following diagram by
adjusting someone else\'s, so it may look a bit odd.
https://i.imgur.com/d2TfZYO.jpg
I\'m a bit confused here because you can trace the current flow and show
the output has both 24V (if the current goes through the \"wrong\" bridge on
the way back) and 12V at the same time, which isn\'t possible. Can someone
explain what would happen in this circuit?
Any way to make this work? I want current flowing through both halves of
the secondary all the time. But I want half the full secondary\'s voltage.
There is nothing you can do to increase the power if your load is
resistive - but if it is smoothed with a capacitor, there might be.
Using a choke between the rectifiers and the first smoothing capacitor
will even-out the current peaks through the transformer windings and
reduce the losses which are proportional to the square of the current.
You may then be able to run the transformer at a higher current than the
\'official\' rating, which is usually specified for peaky rectified
current.
The output voltage will then be approximately the RMS voltage of the
waveform
Average is 2/pi times peak, which is a bit less.
(minus diode drops, the transformer winding resistance losses
and the choke resistance losses), not the rectified peak voltage. (minus
diode drops and somewhat larger transformer winding resistance loses).
Whether this ultimately equates to more *power*, rather than just more
current, will depend on the parameters of transformer and choke.
Another way to increse the power handling of an particlar size of
transformer is to increase the frequency. This may not be practical for
a mains transformer - and you will soon run into greater losses from
eddy currents in the core at higher frequencies - but it is commonly
used to reduce the size and weight of transformers in aircraft.
Power handling of a transformer or resistor or inductor improves with
air flow or heat sinking. They are usually specified in still air.
Good idea, I shall add those accordingly, got loads of heatsinks and fans kicking about.
Can I do the same with a SMPS? Mind you they\'re probably limited so I\'d need to alter the circuit.
Yes, air flow increases the power capability of most things. Resistors
can be run at 1.5 to as much as 5x rated power with a lot of air. This
is usually best determined by testing.
A flyback power supply may never put out much more than design
power... probably not cooling limited.
They get damn hot. What else would limit it?
Energy stored in the inductor times the pulse rate is the limit of
output power, and both are usually limited.
Cooling will improve reliability if it\'s getting hot.
One of them (12V 83A) smells bad at only 60A. But it\'s been running 24/7 like that for a couple of years.
Unlikely to be a flyback, at that power.
Another (12V 40A) gave up after running at half power for 4 months. When I opened it I found the two largest transistors weren\'t tightly attached to the heatsink, and were dead shorts across all three pins. Would that have killed anything else in the circuit? I\'ve ordered two replacement transistors (J13009). To be fair, it used to power a scuba compressor (at 40A) which made a lot of vibration.
Bad heat sinking for sure.
Heat skinks are expensive so that\'s where people skrimp. More air will
certainly make power supplies more reliable.
Vibration may have loosened the screws on the transistors.
C
Commander Kinsey
Guest
On Sat, 08 Apr 2023 10:19:01 +0100, Paul <nospam@needed.invalid> wrote:
Ah! So the AND gate is actually a symbol meaning \"any component\". Not very intuitive.
On 4/5/2023 7:09 PM, Commander Kinsey wrote:
Thanks! It just so happens I just downloaded LTSpice, I\'d not got round to working out how to use it though. Where do you get the components to insert? I couldn\'t find the voltage source for example, only buttons for a handful of components.
This shows a voltage source symbol.
[Picture]
https://i.postimg.cc/28LzTPQY/component.gif
Ah! So the AND gate is actually a symbol meaning \"any component\". Not very intuitive.
C
Commander Kinsey
Guest
On Fri, 14 Apr 2023 15:34:41 +0100, John Larkin <jjlarkin@highlandtechnology.com> wrote:
Never made much heat when the heatsinks were in place.
What\'s weird is I have two of the 83A ones, the new one makes a quarter of the heat. Same design, same manufacturer, looks a little bit different peeking through the vents. Can they really improve efficiency that much?
On Fri, 14 Apr 2023 14:54:11 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Thu, 13 Apr 2023 18:44:47 +0100, John Larkin <jjlarkin@highlandtechnology.com> wrote:
On Thu, 13 Apr 2023 16:12:17 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Tue, 04 Apr 2023 04:04:47 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
On Mon, 03 Apr 2023 22:12:31 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Mon, 27 Mar 2023 18:55:25 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
On Mon, 27 Mar 2023 17:55:51 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Commander Kinsey <CK1@nospam.com> wrote:
I have a centre tapped transformer I wanted to get the most power out of.
Thinking a traditional full wave rectifier (just a diode on each side,
calling the centre tap 0V at the output) is only running current through
one half of the secondary at a time, which is inefficient (think of
P=i^2R), I thought about putting a bridge rectifier on each half, then
connecting the result in parallel. I made the following diagram by
adjusting someone else\'s, so it may look a bit odd.
https://i.imgur.com/d2TfZYO.jpg
I\'m a bit confused here because you can trace the current flow and show
the output has both 24V (if the current goes through the \"wrong\" bridge on
the way back) and 12V at the same time, which isn\'t possible. Can someone
explain what would happen in this circuit?
Any way to make this work? I want current flowing through both halves of
the secondary all the time. But I want half the full secondary\'s voltage.
There is nothing you can do to increase the power if your load is
resistive - but if it is smoothed with a capacitor, there might be.
Using a choke between the rectifiers and the first smoothing capacitor
will even-out the current peaks through the transformer windings and
reduce the losses which are proportional to the square of the current.
You may then be able to run the transformer at a higher current than the
\'official\' rating, which is usually specified for peaky rectified
current.
The output voltage will then be approximately the RMS voltage of the
waveform
Average is 2/pi times peak, which is a bit less.
(minus diode drops, the transformer winding resistance losses
and the choke resistance losses), not the rectified peak voltage. (minus
diode drops and somewhat larger transformer winding resistance loses).
Whether this ultimately equates to more *power*, rather than just more
current, will depend on the parameters of transformer and choke.
Another way to increse the power handling of an particlar size of
transformer is to increase the frequency. This may not be practical for
a mains transformer - and you will soon run into greater losses from
eddy currents in the core at higher frequencies - but it is commonly
used to reduce the size and weight of transformers in aircraft.
Power handling of a transformer or resistor or inductor improves with
air flow or heat sinking. They are usually specified in still air.
Good idea, I shall add those accordingly, got loads of heatsinks and fans kicking about.
Can I do the same with a SMPS? Mind you they\'re probably limited so I\'d need to alter the circuit.
Yes, air flow increases the power capability of most things. Resistors
can be run at 1.5 to as much as 5x rated power with a lot of air. This
is usually best determined by testing.
A flyback power supply may never put out much more than design
power... probably not cooling limited.
They get damn hot. What else would limit it?
Energy stored in the inductor times the pulse rate is the limit of
output power, and both are usually limited.
Cooling will improve reliability if it\'s getting hot.
One of them (12V 83A) smells bad at only 60A. But it\'s been running 24/7 like that for a couple of years.
Unlikely to be a flyback, at that power.
Another (12V 40A) gave up after running at half power for 4 months. When I opened it I found the two largest transistors weren\'t tightly attached to the heatsink, and were dead shorts across all three pins. Would that have killed anything else in the circuit? I\'ve ordered two replacement transistors (J13009). To be fair, it used to power a scuba compressor (at 40A) which made a lot of vibration.
Bad heat sinking for sure.
Heat skinks are expensive so that\'s where people skrimp. More air will
certainly make power supplies more reliable.
Vibration may have loosened the screws on the transistors.
Never made much heat when the heatsinks were in place.
What\'s weird is I have two of the 83A ones, the new one makes a quarter of the heat. Same design, same manufacturer, looks a little bit different peeking through the vents. Can they really improve efficiency that much?
C
Commander Kinsey
Guest
On Fri, 14 Apr 2023 15:34:41 +0100, John Larkin <jjlarkin@highlandtechnology.com> wrote:
Never made much heat when the heatsinks were in place.
What\'s weird is I have two of the 83A ones, the new one makes a quarter of the heat. Same design, same manufacturer, looks a little bit different peeking through the vents. Can they really improve efficiency that much?
On Fri, 14 Apr 2023 14:54:11 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Thu, 13 Apr 2023 18:44:47 +0100, John Larkin <jjlarkin@highlandtechnology.com> wrote:
On Thu, 13 Apr 2023 16:12:17 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Tue, 04 Apr 2023 04:04:47 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
On Mon, 03 Apr 2023 22:12:31 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Mon, 27 Mar 2023 18:55:25 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
On Mon, 27 Mar 2023 17:55:51 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Commander Kinsey <CK1@nospam.com> wrote:
I have a centre tapped transformer I wanted to get the most power out of.
Thinking a traditional full wave rectifier (just a diode on each side,
calling the centre tap 0V at the output) is only running current through
one half of the secondary at a time, which is inefficient (think of
P=i^2R), I thought about putting a bridge rectifier on each half, then
connecting the result in parallel. I made the following diagram by
adjusting someone else\'s, so it may look a bit odd.
https://i.imgur.com/d2TfZYO.jpg
I\'m a bit confused here because you can trace the current flow and show
the output has both 24V (if the current goes through the \"wrong\" bridge on
the way back) and 12V at the same time, which isn\'t possible. Can someone
explain what would happen in this circuit?
Any way to make this work? I want current flowing through both halves of
the secondary all the time. But I want half the full secondary\'s voltage.
There is nothing you can do to increase the power if your load is
resistive - but if it is smoothed with a capacitor, there might be.
Using a choke between the rectifiers and the first smoothing capacitor
will even-out the current peaks through the transformer windings and
reduce the losses which are proportional to the square of the current.
You may then be able to run the transformer at a higher current than the
\'official\' rating, which is usually specified for peaky rectified
current.
The output voltage will then be approximately the RMS voltage of the
waveform
Average is 2/pi times peak, which is a bit less.
(minus diode drops, the transformer winding resistance losses
and the choke resistance losses), not the rectified peak voltage. (minus
diode drops and somewhat larger transformer winding resistance loses).
Whether this ultimately equates to more *power*, rather than just more
current, will depend on the parameters of transformer and choke.
Another way to increse the power handling of an particlar size of
transformer is to increase the frequency. This may not be practical for
a mains transformer - and you will soon run into greater losses from
eddy currents in the core at higher frequencies - but it is commonly
used to reduce the size and weight of transformers in aircraft.
Power handling of a transformer or resistor or inductor improves with
air flow or heat sinking. They are usually specified in still air.
Good idea, I shall add those accordingly, got loads of heatsinks and fans kicking about.
Can I do the same with a SMPS? Mind you they\'re probably limited so I\'d need to alter the circuit.
Yes, air flow increases the power capability of most things. Resistors
can be run at 1.5 to as much as 5x rated power with a lot of air. This
is usually best determined by testing.
A flyback power supply may never put out much more than design
power... probably not cooling limited.
They get damn hot. What else would limit it?
Energy stored in the inductor times the pulse rate is the limit of
output power, and both are usually limited.
Cooling will improve reliability if it\'s getting hot.
One of them (12V 83A) smells bad at only 60A. But it\'s been running 24/7 like that for a couple of years.
Unlikely to be a flyback, at that power.
Another (12V 40A) gave up after running at half power for 4 months. When I opened it I found the two largest transistors weren\'t tightly attached to the heatsink, and were dead shorts across all three pins. Would that have killed anything else in the circuit? I\'ve ordered two replacement transistors (J13009). To be fair, it used to power a scuba compressor (at 40A) which made a lot of vibration.
Bad heat sinking for sure.
Heat skinks are expensive so that\'s where people skrimp. More air will
certainly make power supplies more reliable.
Vibration may have loosened the screws on the transistors.
Never made much heat when the heatsinks were in place.
What\'s weird is I have two of the 83A ones, the new one makes a quarter of the heat. Same design, same manufacturer, looks a little bit different peeking through the vents. Can they really improve efficiency that much?
C
Commander Kinsey
Guest
On Fri, 14 Apr 2023 15:34:41 +0100, John Larkin <jjlarkin@highlandtechnology.com> wrote:
Never made much heat when the heatsinks were in place.
What\'s weird is I have two of the 83A ones, the new one makes a quarter of the heat. Same design, same manufacturer, looks a little bit different peeking through the vents. Can they really improve efficiency that much?
On Fri, 14 Apr 2023 14:54:11 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Thu, 13 Apr 2023 18:44:47 +0100, John Larkin <jjlarkin@highlandtechnology.com> wrote:
On Thu, 13 Apr 2023 16:12:17 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Tue, 04 Apr 2023 04:04:47 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
On Mon, 03 Apr 2023 22:12:31 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Mon, 27 Mar 2023 18:55:25 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
On Mon, 27 Mar 2023 17:55:51 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Commander Kinsey <CK1@nospam.com> wrote:
I have a centre tapped transformer I wanted to get the most power out of.
Thinking a traditional full wave rectifier (just a diode on each side,
calling the centre tap 0V at the output) is only running current through
one half of the secondary at a time, which is inefficient (think of
P=i^2R), I thought about putting a bridge rectifier on each half, then
connecting the result in parallel. I made the following diagram by
adjusting someone else\'s, so it may look a bit odd.
https://i.imgur.com/d2TfZYO.jpg
I\'m a bit confused here because you can trace the current flow and show
the output has both 24V (if the current goes through the \"wrong\" bridge on
the way back) and 12V at the same time, which isn\'t possible. Can someone
explain what would happen in this circuit?
Any way to make this work? I want current flowing through both halves of
the secondary all the time. But I want half the full secondary\'s voltage.
There is nothing you can do to increase the power if your load is
resistive - but if it is smoothed with a capacitor, there might be.
Using a choke between the rectifiers and the first smoothing capacitor
will even-out the current peaks through the transformer windings and
reduce the losses which are proportional to the square of the current.
You may then be able to run the transformer at a higher current than the
\'official\' rating, which is usually specified for peaky rectified
current.
The output voltage will then be approximately the RMS voltage of the
waveform
Average is 2/pi times peak, which is a bit less.
(minus diode drops, the transformer winding resistance losses
and the choke resistance losses), not the rectified peak voltage. (minus
diode drops and somewhat larger transformer winding resistance loses).
Whether this ultimately equates to more *power*, rather than just more
current, will depend on the parameters of transformer and choke.
Another way to increse the power handling of an particlar size of
transformer is to increase the frequency. This may not be practical for
a mains transformer - and you will soon run into greater losses from
eddy currents in the core at higher frequencies - but it is commonly
used to reduce the size and weight of transformers in aircraft.
Power handling of a transformer or resistor or inductor improves with
air flow or heat sinking. They are usually specified in still air.
Good idea, I shall add those accordingly, got loads of heatsinks and fans kicking about.
Can I do the same with a SMPS? Mind you they\'re probably limited so I\'d need to alter the circuit.
Yes, air flow increases the power capability of most things. Resistors
can be run at 1.5 to as much as 5x rated power with a lot of air. This
is usually best determined by testing.
A flyback power supply may never put out much more than design
power... probably not cooling limited.
They get damn hot. What else would limit it?
Energy stored in the inductor times the pulse rate is the limit of
output power, and both are usually limited.
Cooling will improve reliability if it\'s getting hot.
One of them (12V 83A) smells bad at only 60A. But it\'s been running 24/7 like that for a couple of years.
Unlikely to be a flyback, at that power.
Another (12V 40A) gave up after running at half power for 4 months. When I opened it I found the two largest transistors weren\'t tightly attached to the heatsink, and were dead shorts across all three pins. Would that have killed anything else in the circuit? I\'ve ordered two replacement transistors (J13009). To be fair, it used to power a scuba compressor (at 40A) which made a lot of vibration.
Bad heat sinking for sure.
Heat skinks are expensive so that\'s where people skrimp. More air will
certainly make power supplies more reliable.
Vibration may have loosened the screws on the transistors.
Never made much heat when the heatsinks were in place.
What\'s weird is I have two of the 83A ones, the new one makes a quarter of the heat. Same design, same manufacturer, looks a little bit different peeking through the vents. Can they really improve efficiency that much?
F
Fredxx
Guest
On 15/04/2023 21:07, Commander Kinsey wrote:
Don\'t worry, it\'s well beyond your capability.
On Sat, 08 Apr 2023 10:19:01 +0100, Paul <nospam@needed.invalid> wrote:
On 4/5/2023 7:09 PM, Commander Kinsey wrote:
Thanks! It just so happens I just downloaded LTSpice, I\'d not got
round to working out how to use it though. Where do you get the
components to insert? I couldn\'t find the voltage source for
example, only buttons for a handful of components.
This shows a voltage source symbol.
   [Picture]
   https://i.postimg.cc/28LzTPQY/component.gif
Ah! So the AND gate is actually a symbol meaning \"any component\". Not
very intuitive.
Don\'t worry, it\'s well beyond your capability.
P
Peeler
Guest
On Sun, 16 Apr 2023 19:51:44 +0100, Fredxx, the notorious, troll-feeding,
senile smartass, blathered again:
> Don\'t worry, it\'s well beyond your capability.
Just like your incapability to resist the dumbest baits the troll keeps
setting out for you! LOL
senile smartass, blathered again:
> Don\'t worry, it\'s well beyond your capability.
Just like your incapability to resist the dumbest baits the troll keeps
setting out for you! LOL
J
John Larkin
Guest
On Sat, 15 Apr 2023 21:07:26 +0100, \"Commander Kinsey\"
<CK1@nospam.com> wrote:
You don\'t use LT Spice?
<CK1@nospam.com> wrote:
On Sat, 08 Apr 2023 10:19:01 +0100, Paul <nospam@needed.invalid> wrote:
On 4/5/2023 7:09 PM, Commander Kinsey wrote:
Thanks! It just so happens I just downloaded LTSpice, I\'d not got round to working out how to use it though. Where do you get the components to insert? I couldn\'t find the voltage source for example, only buttons for a handful of components.
This shows a voltage source symbol.
[Picture]
https://i.postimg.cc/28LzTPQY/component.gif
Ah! So the AND gate is actually a symbol meaning \"any component\". Not very intuitive.
You don\'t use LT Spice?
P
Peeler
Guest
On Sun, 16 Apr 2023 20:05:49 -0700, John Larkin, another obviously brain
dead, troll-feeding senile asshole, blathered:
> You don\'t use LT Spice?
The only thing that attention-starved gay wanker uses is you troll-feeding
senile assholes to feed him! And he seems to be very very good at that!
dead, troll-feeding senile asshole, blathered:
> You don\'t use LT Spice?
The only thing that attention-starved gay wanker uses is you troll-feeding
senile assholes to feed him! And he seems to be very very good at that!
C
Commander Kinsey
Guest
On Mon, 17 Apr 2023 04:05:49 +0100, John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:
I used PSpice a long long time ago.
On Sat, 15 Apr 2023 21:07:26 +0100, \"Commander Kinsey\"
CK1@nospam.com> wrote:
On Sat, 08 Apr 2023 10:19:01 +0100, Paul <nospam@needed.invalid> wrote:
On 4/5/2023 7:09 PM, Commander Kinsey wrote:
Thanks! It just so happens I just downloaded LTSpice, I\'d not got round to working out how to use it though. Where do you get the components to insert? I couldn\'t find the voltage source for example, only buttons for a handful of components.
This shows a voltage source symbol.
[Picture]
https://i.postimg.cc/28LzTPQY/component.gif
Ah! So the AND gate is actually a symbol meaning \"any component\". Not very intuitive.
You don\'t use LT Spice?
I used PSpice a long long time ago.