AndrewT said:
jnb said:
Hi,
if you allow full current at start up you will need a big mains fuse. That is the main disadvantage you should try to avoid.
There is also the possibility that the distribution board breaker will trip each time you start up. Finally the power draw will momentarily pull down the voltage sent to the rest house. Some equipment may trip, and lights may dim and TV/monitor distort.
If your transformer is 120Vac 600VA, then theoretically it can operate all day with a 5A mains fuse. But at start up it may require a 15A mains fuse (or possibly even higher) to avoid nuisance tripping. There is a potential for 1.8kVA passing through a fault and the fuse not rupturing. That is an increased fire risk.
you can allways put extra turns on the transformer primery.
this will lower the mag current,reducing mechanical noise and magnetic field,and will lower the inrush.
but this adds to the cost!
and no transformer companiy will do that!
this will lower the mag current,reducing mechanical noise and magnetic field,and will lower the inrush.
but this adds to the cost!
and no transformer companiy will do that!
Adding primary turns also makes the transformer less efficient because of increased copper losses.
adding more turns to the primery winding does not necessarly mean more copper losses!
but will increase cost per transformer!
but will increase cost per transformer!
with toridals people put cost over qualaty.
by adding copper over and above what is needed,means lower mag current.
less noise from transformer at higher cost.
yet if you go up several gages with the primary winding making a better transformer.
some people will say it is not a well desineded transformer becouse it could have more copper losses.
Well i give you the audio grade transformer!
andy
by adding copper over and above what is needed,means lower mag current.
less noise from transformer at higher cost.
yet if you go up several gages with the primary winding making a better transformer.
some people will say it is not a well desineded transformer becouse it could have more copper losses.
Well i give you the audio grade transformer!
andy
More primary turns also means better resistance to saturation. The company I worked at used to use a safety margin on the primary to ensure everything was nice. But I think they were undercut by a lot of the toroidal prices at places like Rapid and CPC.
also as i have used many toridal companies to make my transformers for use in my own amplifiers,i can tell you i have seen a lot of Trash out there.
the transformer is at the heart of an amplifier and most people have no idea as to how important it is.
antrim transformers make the best independent toridals out there.
followed by nortel.
the transformer is at the heart of an amplifier and most people have no idea as to how important it is.
antrim transformers make the best independent toridals out there.
followed by nortel.
its the iron core that saturates.
in big amplifiers the saturation point is also important as some people run big amplifiers on generators.
if saturation is set to around 255-260v then the mains fuse will blow with out damaging the amplifier.
when given over voltage.
in big amplifiers the saturation point is also important as some people run big amplifiers on generators.
if saturation is set to around 255-260v then the mains fuse will blow with out damaging the amplifier.
when given over voltage.
to show the importance of the transformer and its quality and the difaculty getting it at the corect cost.
I have 3 toriod winders to make my own on.
this gives me the best transformers in audio!
at the best price.
and total control of the transformer!
when i developed the origanal aura amplifier i used several transformer suppliers.
eg holden and fisher and cotswaled electronics (avel lindberg)
the cotswald were trash with a 20% failed in the field.
this can kill your companie!
yet i never changed a holden and fisher.
I have 3 toriod winders to make my own on.
this gives me the best transformers in audio!
at the best price.
and total control of the transformer!
when i developed the origanal aura amplifier i used several transformer suppliers.
eg holden and fisher and cotswaled electronics (avel lindberg)
the cotswald were trash with a 20% failed in the field.
this can kill your companie!
yet i never changed a holden and fisher.
MUST subscribe to this thread...
Specially since i will be building a power supply very soon using a 2KVA toroid, will NEED a soft start specially when its gonna be tied to almost 1F worth of caps on the secondary side 😱
Specially since i will be building a power supply very soon using a 2KVA toroid, will NEED a soft start specially when its gonna be tied to almost 1F worth of caps on the secondary side 😱
You will need something to protect the diodes as well.
With a low resistance on the power transformer secondary, there could be 1,000A currents flowing with a 1A load and 1F of capacitance.
With a low resistance on the power transformer secondary, there could be 1,000A currents flowing with a 1A load and 1F of capacitance.
Toroid is a Custom Wound unit by Plitron LONO ( low noise with shielded windings, potted and canned ) unit.
Dual 40VAC @ 25A Each + dual 12VAC @10A Each + single 5VAC @ 5A.
Rectifiers are RURG75120 Rated at 75A continuous and 150A repetitive current, but using a redundant setup so there going to be 8 rectifying diodes with o.1uF film caps across them to reduce switching noise.
The Caps are 12 x 18000uF @ 100V, each decoupled with 10uF film caps and 25K 1/4w 2% resistor. Across the main buss ( Vcc and Vee ) there will be a 47uF 300V Film cap for further filtering of noise.
The whole thing will be separated onto 2 boards.
The first board will house the rectifiers, decoupling ( 8 x 0.1uF and 1 X 47uF Film ) and 2 x 1000uF caps. Second board will house the cap bank itself.
The arrangement of the caps will be a 3x2 + 3x2 where power will be fed in at the middle of the board and will be flowing towards the edges to the 2 modules it will be supplying.
I will be posting a Schematic Very Shortly.
Dual 40VAC @ 25A Each + dual 12VAC @10A Each + single 5VAC @ 5A.
Rectifiers are RURG75120 Rated at 75A continuous and 150A repetitive current, but using a redundant setup so there going to be 8 rectifying diodes with o.1uF film caps across them to reduce switching noise.
The Caps are 12 x 18000uF @ 100V, each decoupled with 10uF film caps and 25K 1/4w 2% resistor. Across the main buss ( Vcc and Vee ) there will be a 47uF 300V Film cap for further filtering of noise.
The whole thing will be separated onto 2 boards.
The first board will house the rectifiers, decoupling ( 8 x 0.1uF and 1 X 47uF Film ) and 2 x 1000uF caps. Second board will house the cap bank itself.
The arrangement of the caps will be a 3x2 + 3x2 where power will be fed in at the middle of the board and will be flowing towards the edges to the 2 modules it will be supplying.
I will be posting a Schematic Very Shortly.
Here's the Schematic...
Input Please....
An externally hosted image should be here but it was not working when we last tested it.
Input Please....
Relays vs Thermistors
It's important to understand where the inrush current occurs and what components require protection. Bridge diodes are probably the most prone to failure. A transformer is likely to saturate rather than sustain damage due to low rep overload events. Most electrolytic capacitors do not respond well to sudden di/dt conditions, and I'm not aware of any manufacturer who specifies di/dt limits. Finally the power switch is prone to arcing damage. I chose to use a relay/delay circuit over a thermistor because the former allowed precise control over (1) startup resistance and power limits of resistor, (2) duration of high resistance, (3) near zero resistance during normal operating conditions. The relay was placed in series with the AC mains thereby protecting all the above mentioned components.
It's important to understand where the inrush current occurs and what components require protection. Bridge diodes are probably the most prone to failure. A transformer is likely to saturate rather than sustain damage due to low rep overload events. Most electrolytic capacitors do not respond well to sudden di/dt conditions, and I'm not aware of any manufacturer who specifies di/dt limits. Finally the power switch is prone to arcing damage. I chose to use a relay/delay circuit over a thermistor because the former allowed precise control over (1) startup resistance and power limits of resistor, (2) duration of high resistance, (3) near zero resistance during normal operating conditions. The relay was placed in series with the AC mains thereby protecting all the above mentioned components.
"A picturecis worth a thousand words" someone once said.
I mean its a diy site, might as well have people share their ideas and circuits and try and improve to achieve the best suitable solution.
I was going to use 4 x 5w resistors in paralel with a relay across them to latch after a set ammount of time driven by a 555 timer.
I mean its a diy site, might as well have people share their ideas and circuits and try and improve to achieve the best suitable solution.
I was going to use 4 x 5w resistors in paralel with a relay across them to latch after a set ammount of time driven by a 555 timer.
post114.
The rCLC PSU imparts a very high ripple on the first C.
Simulate the upper half in psud11 and see how bad the ripple is.
You will need very high quality, low esr, high ripple capacitors for this first C. Or multiple 1mF in parallel and kept cool.
The rCLC PSU imparts a very high ripple on the first C.
Simulate the upper half in psud11 and see how bad the ripple is.
You will need very high quality, low esr, high ripple capacitors for this first C. Or multiple 1mF in parallel and kept cool.
Try doing a simulation on a constant 1A load on a 1F cap and see what the repetitive peak diode currents will be.
I gave up on using PSUD II a long time ago as it doesn't allow for a specific circuit to be tested and library is very limited.
Pertaining to diagram posted above...
The bridges as posted above running in tanderm configuration will be able to take 600A of Peak repetitive current, that's 15 times more than what my Toroid will be able to deliver. Also the smoothing caps are only 1000uF 100V Nichicon FW's decoupled with 10uF 250V BC Film caps. the third film cap across Vcc and Vee is a 47uF 300VDC BC Film Cap to further remove noise.
The 18000uF 100V caps are Panasonic TUP's and by no means any of these are cheap caps.
Also with the soft start latched for 5 secs or so should allow a "pre-charge" condition to take place and allow a partial charge to occur.
will post a quick schematic of the soft start circuit im planning to use.
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