Using Inrush Current Limiters

[hollowman]

The datasheet for the CL-series (inrush current limiters) instructs one to place the device AFTER the rectifier bridge. INSTEAD, can one safely place this device in series with the main 120 VAC line? My objective is to smooth the inrush current BEFORE the main transformer.

Other ref for this device:
http://parts.digikey.com/1/parts/705...ush-cl-60.html

[ifrythings]

They say "it's commonly used" that way, I almost always see it before the bridge rectifier in most SMPS applications.

They may recommend it there for the fact that DC current will heat it up faster then AC current will?

[hollowman]

Originally posted by ifrythings
They say "it's commonly used" that way, I almost always see it before the bridge rectifier in most SMPS applications.

They may recommend it there for the fact that DC current will heat it up faster than AC current will?

I assume, then, that one would place it in series with the HOT line as it comes in, just before the main switch (or does it make a difference?).

BTW, I'm not using it for SMPS applications. So I don't ultimately know how useful or effective this device is. It was suggested by someone in this thread.

[Anthony C Smith]

I would assume from your comments that you are inrush limiting a transformer?
I use a similar epcos device, or more accurately two, one in the live and one in the neutral, rated 22R cold and 2.5A RMS for a commercial 625VA torroid;
This has additional benifits in en61000-3-2 performance.
regards

[AndrewT]

Hi,
a Thermistor before the transformer and after the transformer are doing two different things.

Thermistor before the transformer reduces the current pulse from the mains while the transformer is establishing it's flux getting ready to deliver power.

Thermistor after the transformer reduces the current pulse going to charge up the smoothing capacitance after the transformer has started to deliver power.
The two thermistors will be chosen for these different duties and purposes.
Fitting both is OK since they each do something different.

I recommend that bypass relays with different delays be placed around each Thermistor. This reduces the PSU impedance (improving amplifier performance) and allows the Thermistor to cool for the next start up.

[hollowman]

Originally posted by Anthony C Smith
I would assume from your comments that you are inrush limiting a transformer?

It's an external PSU for a Philips CD650 CDP. It contains several mini toroid transformers dedicated to IC-specific rectifier/regulator combos.
The PSU also has a balance transformer that powers the CD650's main AC line.