I have been through various threads about how to solve inrush problems So many "meanings" on what is the best, confuses me.
Now I have decided to try the simpel solution: NTC
My amplifiers are both Slewmaster(classA/B); one with two tranformers(2x700VA), DC voltage 2x65V and twin 60000uF condenserbank. I have some NTC 10 ohm 16A.
In this thread Andrew T wrote: If you use a 220/240Vac primary then a high power transformer needs two CL60 in series. That gives the same current limiting as the two CL60 to the twin 110/120Vac primaries.
Shall I use 2xNTC to one transformer and 2x NTC to the other transformer?
The other Slewmaster have a 2.2KVA transformer(same data as the two others). If I have understood it right; here 2xNTC will be correct?
Eivind S
Now I have decided to try the simpel solution: NTC
My amplifiers are both Slewmaster(classA/B); one with two tranformers(2x700VA), DC voltage 2x65V and twin 60000uF condenserbank. I have some NTC 10 ohm 16A.
In this thread Andrew T wrote: If you use a 220/240Vac primary then a high power transformer needs two CL60 in series. That gives the same current limiting as the two CL60 to the twin 110/120Vac primaries.
Shall I use 2xNTC to one transformer and 2x NTC to the other transformer?
The other Slewmaster have a 2.2KVA transformer(same data as the two others). If I have understood it right; here 2xNTC will be correct?
Eivind S
Before you make a decision I strongly suggest you read this Soft-Start Circuit For Power Amps. There is such a thing as too simple and what you are considering could, under certain circumstances, be not fit for purpose.
Goodness, why do you use such big transformers? No wonder you have in-rush current problems! NTC is really not your best solution. Besides the inrush current could be several times the 16A rating of the NTC. Maybe just purchase a soft start from Siemens or GEC and fit in the amps.
Your simplest method is having two switches, one bringing your transformers up in "stand-by" limiting the current by several orders of magnitude, then switch on the next switch that places full supply on them.
Your simplest method is having two switches, one bringing your transformers up in "stand-by" limiting the current by several orders of magnitude, then switch on the next switch that places full supply on them.
The close rated fuse for a single 700VA 230Vac transformer is T3.1A
That fuse will survive many cold start ups when the current is limited for <=6.2Apk
For 230Vac you would need a total primary circuit resistance of ~37ohms
If your primary is 1ohm then your added resistance would be 36r
But you may find that the T3.1A fuse survives many start ups with considerably less than 36r of added resistance.
You could try an added resistance of 30r, and/or 24r, and/or 20r and see what life you get from the mains fuse.
I know that a T3.1A fuse on a nominal 240Vac mains supply, that they survive two times the rated current as the start up peak repeatedly.
That fuse will survive many cold start ups when the current is limited for <=6.2Apk
For 230Vac you would need a total primary circuit resistance of ~37ohms
If your primary is 1ohm then your added resistance would be 36r
But you may find that the T3.1A fuse survives many start ups with considerably less than 36r of added resistance.
You could try an added resistance of 30r, and/or 24r, and/or 20r and see what life you get from the mains fuse.
I know that a T3.1A fuse on a nominal 240Vac mains supply, that they survive two times the rated current as the start up peak repeatedly.
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