About my Thoroid transformer...

Any connection between the bolt head and the chassis will result in a shorted turn

but if its fitted in a low profile metal enclosure
then it may be possible for the top to be deformed and touch the bolt head if pressure is applied !

Attachment 26393

John

Quote:

---

Originally Posted by john swift

Any connection between the bolt head and the chassis will result in a shorted turn

but if its fitted in a low profile metal enclosure
then it may be possible for the top to be deformed and touch the bolt head if pressure is applied !

Attachment 26393

John

---

How about the lower end? The nut will be in contact there right?

the lower end is OK as the chassis , bolt and top mounting disk don't form a complete turn around the toroidal core

its only when you close the loop by connecting the mounting disk to the chassis by a conductor outside the core

John

Quote:

---

Originally Posted by john swift

the lower end is OK as the chassis , bolt and top mounting disk don't form a complete turn around the toroidal core

its only when you close the loop by connecting the mounting disk to the chassis by a conductor outside the core

John

---

Allright, thanks! :thumsup:
When were at it, what type of fuses would you use for a PSU?

Quote:

---

Originally Posted by JW1977

Allright, thanks! :thumsup:
When were at it, what type of fuses would you use for a PSU?

---

For a toroidal transformer feeding a rectifier/smoothing capacitors you'll need a time delay (T) fuse as the switch on current surge can be VERY large.

However if you have a fairly constant power drain you can reduce the surge by fitting a NTC thermistor in series

Any idea what the transformers VA rating is ?

As a toroidal transformer inrush current is very large
I would not be supprised if you need a fuse 3 or 4 times what the VA rating would indicate

if you have a 600VA transformer
you may have to use a HRC 10A mains fuse (HRC = High Rupture Capacity)

and check what type of circuit breaker is supplying the radial circuit your mains socket connected to

for example
a type B breaker trips at 3 to 5 times the full load current operating time 0.04 To 13 Sec

a type C breaker trips at 5 to 10 times the full load current operating time 0.04 To 5 Sec

John

PS

if the transformer is large enough you may have to consider using an inrush current limiter
some examples here -
https://sound-au.com/articles/inrush.htm

PPS
more details of a Soft-Start Circuit
https://sound-au.com/project39.htm

Quote:

---

Originally Posted by Voicecoil

For a toroidal transformer feeding a rectifier/smoothing capacitors you'll need a time delay (T) fuse as the switch on current surge can be VERY large.

However if you have a fairly constant power drain you can reduce the surge by fitting a NTC thermistor in series

---

Allright, i have to keep looking into that...

Quote:

---

Originally Posted by john swift

Any idea what the transformers VA rating is ?

As a toroidal transformer inrush current is very large
I would not be supprised if you need a fuse 3 or 4 times what the VA rating would indicate

if you have a 600VA transformer
you may have to use a HRC 10A mains fuse (HRC = High Rupture Capacity)

and check what type of circuit breaker is supplying the radial circuit your mains socket connected to

for example
a type B breaker trips at 3 to 5 times the full load current operating time 0.04 To 13 Sec

a type C breaker trips at 5 to 10 times the full load current operating time 0.04 To 5 Sec

John

PS

if the transformer is large enough you may have to consider using an inrush current limiter
some examples here -
https://sound-au.com/articles/inrush.htm

PPS
more details of a Soft-Start Circuit
https://sound-au.com/project39.htm

---

Yes, its 800VA. Got some Reading to do about this, thanks!