as the title says, my amp which will probably never gte made is going to have multiple transformers (not sure how many yet, atleast 3... maybe 6 or 7.. lol) they are 250VA each, and I believe (though I have no tested yet) that when powering up a few of these at once, it will be bye bye fuse... so, my idea, is to connect them in sequence.... so... when I flick the power switch, the centre transformer instantly gets power, 2 seconds later, the next 2 transformers are powered up, then the next 2, then the final two... all 2 seconds apart, then 2 seconds later again (unless I don't need to do this) the rails will be applied to the amplifier PCBs..... alot of mucking around I know.... but I like the idea.. 
3 or 4 relays, and a simple circuit... any ideas or sugestions?? THANX!!
3 or 4 relays, and a simple circuit... any ideas or sugestions?? THANX!!
If you have 10A 230V in aus as well, you can power up 1kVA at a time, the bigger deal is actually to do so with the load disconnected from the trafo. So if you power them up in batches of 4*250VA and connect the load a second or so after that you should be fine.
The startup power required by a trafo is 5*nominel rating, the mains fuses will tolerate the startup if calculated 2.5 to 3* nominal rating of the trafo.
Magura
The startup power required by a trafo is 5*nominel rating, the mains fuses will tolerate the startup if calculated 2.5 to 3* nominal rating of the trafo.
Magura
Magura said:
The startup power required by a trafo is 5*nominel rating, the mains fuses will tolerate the startup if calculated 2.5 to 3* nominal rating of the trafo.
Magura
wouldn't that depend on the size of the core? powering up just one of these transformers with nothing on the secondary causes enough load to cause the voltage to drop enough for the lights to flash dimmer for a fraction of a second (like a fridge does when the compressor kicks in)
Magura said:
ok..... my toroidals are about....
Outside Diameter: 130mm
Inside Diameter: 40mm
Height: 65mm
that includes the wire
lol which (assuming that site includes the windings in their dimensions) is the same as a 400VA toroidal EDIT: they weigh about 4kgs each (hard to get an accurate weight, no decent scales
)
You probably don't really need to go to the trouble of sequencing them, just apply a soft start to the lot. Use a high power resistor (20 to 50W or so) in series with the primaries, with a normally open set of relay contacts across the resistor. The relay coil would be connected to one of the transformers' secondaries. The surge current will cause a voltage drop across the resistor, charging your supply filter capacitors slowly, until the relay coil has enough voltage across it to pull in, shorting the resistor and applying full mains to the transformers. This works well with toroidals, as they have a higher inrush current due to their tighter coupling.
Cheers
Cheers
Centauri said:
I know I don't NEED the sequence thing, and I could do what you suggested, but I just don't like the idea.... I have even considered just mounting 3 or 4 switches on the front, and switching one on at a time
that way, I could leave the last 2 transformers off, and run the amp with lower voltage rails if I didn't need all the power lol- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.