Hi everyone. How are you all ??
I have still more unanswered queries. So here it is. I want to know what's the correct location in step down transformer to connect Fuse ?
I have watched a lot of videos and seen many circuits online. Some have a primary fuse while others have both primary and secondary fuses. Also the primary fuses current rating is different in different transformer and the confusion starts here. Please check out the following links and help me connect the fuse in right away.
IMG_20190616_162205.jpg - Google Drive
IMG_20190616_162254.jpg - Google Drive
Multifunction psu.jpg - Google Drive
Versatile psu2.jpg - Google Drive
I have still more unanswered queries. So here it is. I want to know what's the correct location in step down transformer to connect Fuse ?
I have watched a lot of videos and seen many circuits online. Some have a primary fuse while others have both primary and secondary fuses. Also the primary fuses current rating is different in different transformer and the confusion starts here. Please check out the following links and help me connect the fuse in right away.
IMG_20190616_162205.jpg - Google Drive
IMG_20190616_162254.jpg - Google Drive
Multifunction psu.jpg - Google Drive
Versatile psu2.jpg - Google Drive
The Valve Wizard site The Valve Wizard gives valuable information in relation to fuse positioning and fuse ratings in valve amplifiers.
Every transformer should have a suitably rated fuse for the primary winding to prevent it catching fire on overload. Ideally this fuse is _not_ accessible from a panel, as its failure is an indication of a serious problem. Its fuse-holder should be marked with the fuse rating and have a warning label about using the correct rating (using the wrong value is a threat to life and limb from building fire). Some types of transformer may be rated to overheat without starting a fire (totally enclosed windings), but don't assume this without documentary evidence!
Typically a primary fuse is slow-blow as the initial current surge on switch on shouldn't rupture it! Its purpose is to protect from sustained overload.
Other fuses on the secondaries can help prevent overload in the first place, but cannot protect the transformer directly (for instance if the primary winding shorts out). Secondary fuses are often protecting their loads as well as the secondary windings.
When a transformer has some small secondaries they may not be substantial enough to blow the primary fuse if they short out - that suggests they need fuses to prevent winding melt-down.
The main secondary winding(s) will blow the primary fuse if shorted, so are less in need of separate protection.
Typically a primary fuse is slow-blow as the initial current surge on switch on shouldn't rupture it! Its purpose is to protect from sustained overload.
Other fuses on the secondaries can help prevent overload in the first place, but cannot protect the transformer directly (for instance if the primary winding shorts out). Secondary fuses are often protecting their loads as well as the secondary windings.
When a transformer has some small secondaries they may not be substantial enough to blow the primary fuse if they short out - that suggests they need fuses to prevent winding melt-down.
The main secondary winding(s) will blow the primary fuse if shorted, so are less in need of separate protection.
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A transformer fuse is large enough not to nuisance blow but small enough to blow before a fire starts.
High power, power amps with big smoothing caps can make things more complicated as the power on surge is significant. Quite a lot of people use cold start anti surge circuits. Either a resistor or thermistor that is quickly shorted out with a relay.
I used a triac and small microcontroller in one of projects and that worked well.
High power, power amps with big smoothing caps can make things more complicated as the power on surge is significant. Quite a lot of people use cold start anti surge circuits. Either a resistor or thermistor that is quickly shorted out with a relay.
I used a triac and small microcontroller in one of projects and that worked well.
The fuse is connected from the AC LINE (HOT/L) to the REAR of the fuse holder, and the FRONT of the fuse holder to the AC POWER switch. Then the switch connects to the TX and the TX return to the AC NETURAL
When some one opens the fuse holder and grabs / touches the fuse and the fuse is GOOD they will not get SHOCKED.
Duke
Hi,
You would think that it should be mandatory that all transformers have in-built thermal fuses to prevent fires. Suitably rated they would prevent any transformer reaching anywhere near ignition temperature. I suppose there's no reason they can't be added, but badly placed, they would not work as well.
regards john
You would think that it should be mandatory that all transformers have in-built thermal fuses to prevent fires. Suitably rated they would prevent any transformer reaching anywhere near ignition temperature. I suppose there's no reason they can't be added, but badly placed, they would not work as well.
regards john
Audio1man
This theory is nice but what happens If You swap the plug on the wall ?
There is no rule that tells You which pin of the plug or harness should be Live.
Either You install a 2 pole switch which cuts the Hot & Neutral or better follow the safety rule and disconnect from the mains before servicing.
As what fuses concern I would install a fuse on the primary side and other /others (depending on outputs) on the secondary side.
If the transformer has it's own thermal fuse on the primary it is already protected against overheating but adding another will perhaps protect it from a transient overload or spike. I would add it anyway since it's easier to replace than the one inside the windings.
This theory is nice but what happens If You swap the plug on the wall ?
There is no rule that tells You which pin of the plug or harness should be Live.
Either You install a 2 pole switch which cuts the Hot & Neutral or better follow the safety rule and disconnect from the mains before servicing.
As what fuses concern I would install a fuse on the primary side and other /others (depending on outputs) on the secondary side.
If the transformer has it's own thermal fuse on the primary it is already protected against overheating but adding another will perhaps protect it from a transient overload or spike. I would add it anyway since it's easier to replace than the one inside the windings.
In this schematics there are C1 (100nF/440V) and R1 (100 ohms/2W) after the primary's fuse. Are these standard values for 230V transformers?
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