Maker Pro
Maker Pro

What's this surge protection component?

D

DaveC

Jan 1, 1970
0
http://home.covad.net/~peninsula/Amp/Surge1.jpg

This is in an audio power amp, in *series* with the fuse and the mains power
switch. I've seen protection devices in parallel with the mains, and chokes
in series, but I can't remember seeing a device such as this in series.

What is it? Is it (in it's former, non-crisp state) appropriate in this
application? Replace with something newer/better? Remove altogether?

Thanks,
 
M

Michael Buchholz

Jan 1, 1970
0
DaveC said:
http://home.covad.net/~peninsula/Amp/Surge1.jpg
What is it? Is it (in it's former, non-crisp state) appropriate in this
application? Replace with something newer/better? Remove altogether?

It is an "inrush limiter", don't know the correct english word for it,
in German it's called a "NTC", a resistor wihich will go down in its
value when heated by the current flowing through it. So it has a high
resistance at startup, effectivly limiting the charging current for the
smoothing capacitors and transformer to something which wouldn't burn the
fuse, and when heated up it is almost a short to provide sufficient current
for the amplifier to operate.

If You have a slow fuse, try shorting it, if the fuse blows, You have to
get a replacement for the NTC.

just my 2 cent, Michael.

P.S.Sorry for my bad English, i'm not a native speaker...
 
D

Don Pearce

Jan 1, 1970
0
It is an "inrush limiter", don't know the correct english word for it,
in German it's called a "NTC", a resistor wihich will go down in its
value when heated by the current flowing through it. So it has a high
resistance at startup, effectivly limiting the charging current for the
smoothing capacitors and transformer to something which wouldn't burn the
fuse, and when heated up it is almost a short to provide sufficient current
for the amplifier to operate.

If You have a slow fuse, try shorting it, if the fuse blows, You have to
get a replacement for the NTC.

just my 2 cent, Michael.

P.S.Sorry for my bad English, i'm not a native speaker...
Michael, your English is better than that of 95% of native speakers.
Useful post as well.

d

_____________________________

http://www.pearce.uk.com
 
M

Michael Buchholz

Jan 1, 1970
0
Michael Buchholz said:
just my 2 cent, Michael.

P.S.Sorry for my bad English, i'm not a native speaker...

Sorry for Crosspost, Clicked 'send' and didn'd see the
Groups...

F'up to sci.electronics.components

Michael.
 
D

DaveC

Jan 1, 1970
0
It is an "inrush limiter", don't know the correct english word for it,
in German it's called a "NTC", a resistor wihich will go down in its
value when heated by the current flowing through it. So it has a high
resistance at startup, effectivly limiting the charging current for the
smoothing capacitors and transformer to something which wouldn't burn the
fuse, and when heated up it is almost a short to provide sufficient current
for the amplifier to operate.

If You have a slow fuse, try shorting it, if the fuse blows, You have to
get a replacement for the NTC.

Thanks, Michael, for your reply. Very helpful.

Can someone please give me the English name for this, and maybe an on-line
reference to a manufacturer or supplier?

Thanks,
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Michael Buchholz <[email protected]>
It is an "inrush limiter", don't know the correct english word for it,

'Inrush limiter' is OK.
in German it's called a "NTC", a resistor wihich will go down in its
value when heated by the current flowing through it.

Properly, 'NTC thermistor' NTC = Negative Temperature Coefficient (of
resistance).
 
F

Frank Pickens

Jan 1, 1970
0
Michael said:
It is an "inrush limiter", don't know the correct english word for it,
in German it's called a "NTC", a resistor wihich will go down in its
value when heated by the current flowing through it. So it has a high
resistance at startup, effectivly limiting the charging current for the
smoothing capacitors and transformer to something which wouldn't burn the
fuse, and when heated up it is almost a short to provide sufficient current
for the amplifier to operate.

If You have a slow fuse, try shorting it, if the fuse blows, You have to
get a replacement for the NTC.

just my 2 cent, Michael.

P.S.Sorry for my bad English, i'm not a native speaker...

Your English is *far* better than many of the 'native' posters seen here.
fp
 
D

DaveC

Jan 1, 1970
0
Properly, 'NTC thermistor' NTC = Negative Temperature Coefficient (of
resistance).

Thanks, John.

Jameco has a list of NTC Varistors:

http://www.jameco.com/Jameco/Products/ProdCT/p091.pdf

These seem like they're transducers for measuring temperature. The specs list
max dissipation as 0.55W. Seems a little lightweight for an inrush limiter. I
think that they are, in this circuit, being required to dissipate much more
than that.

Is this component really appropriate in this application? With the inrush
current this amp has, I just have a hard time seeing any of these components
handling the current.

Is there a better component? A simple resistor, maybe?

Thanks,
 
R

Rein Wiehler

Jan 1, 1970
0
Michael said:
It is an "inrush limiter", don't know the correct english word for it,
in German it's called a "NTC", a resistor wihich will go down in its
value when heated by the current flowing through it. So it has a high
resistance at startup, effectivly limiting the charging current for
the smoothing capacitors and transformer to something which wouldn't
burn the fuse, and when heated up it is almost a short to provide
sufficient current for the amplifier to operate.

If You have a slow fuse, try shorting it, if the fuse blows, You have
to get a replacement for the NTC.

just my 2 cent, Michael.

P.S.Sorry for my bad English, i'm not a native speaker...

are you talking about a resetable fuse?
Raychem is one manufacturer followed by many others.
rw
 
M

Michael Buchholz

Jan 1, 1970
0
are you talking about a resetable fuse?
Raychem is one manufacturer followed by many others.

No, I meant replacing the NTC thermistor by a piece of wire , but this
only
works if the OP has a slow fuse in the Utility panel, otherwise this
fuse will blow due the inrush current not longer being limited.

Michael.
 
S

Spehro Pefhany

Jan 1, 1970
0
Found this application data from a manufacturer:

http://www.ametherm.com/Inrush_Surge_Limiters.htm

and

http://www.ametherm.com/Transformer_case_study.htm

Seems that Jameco carries some of the lightweight models... The above
references show specs up to 36 A.

Check also the Thermometrics line. Note that they don't really limit
if you don't allow them to cool down, so a short blip in the line
voltage can result in a much larger than normal inrush current surge.

Best regards,
Spehro Pefhany
 
J

Jeff

Jan 1, 1970
0
DaveC said:
Thanks, Michael, for your reply. Very helpful.

Can someone please give me the English name for this, and maybe an on-line
reference to a manufacturer or supplier?

It is a NTC - Negative Temperature Coeffiecent resistor. www.digikey.com
sells them. Also note there are many sizes - you have to match them to the
current drawn through it.
 
L

Lewin A.R.W. Edwards

Jan 1, 1970
0
It is an "inrush limiter", don't know the correct english word for it,
in German it's called a "NTC", a resistor wihich will go down in its

In English it's called an NTC, because that's an acronym for Negative
Temperature[Thermal] Coefficient [resistor].
 
R

Ralph Naylor

Jan 1, 1970
0
DaveC said:
Thanks, Michael, for your reply. Very helpful.

Can someone please give me the English name for this, and maybe an on-line
reference to a manufacturer or supplier?

Thanks,
--
DaveC
[email protected]
This is an invalid return address
Please reply in the news group
The KCC marking is for Keystone Carbon Company, now apparently part of
Thermometrics. Here's the NTC page -
http://www.thermometrics.com/htmldocs/numindex.htm
Digikey distributes them - http://dkc3.digikey.com/pdf/T033/0821-0822.pdf

Regards,
Ralph in NH
 
J

John Woodgate

Jan 1, 1970
0
Is this component really appropriate in this application? With the
inrush current this amp has, I just have a hard time seeing any of these
components handling the current.

Just as there are resistors (1/10 W) and resistors (100W), there are
different types of NTC, with vastly different current and power ratings.
Is there a better component? A simple resistor, maybe?

No. A resistor would permanently cut down the supply voltage to the
transformer AND heat up the product.

Other posts have pointed you to more appropriate types of NTC.
 
DaveC said:
Thanks, John.

Jameco has a list of NTC Varistors:

http://www.jameco.com/Jameco/Products/ProdCT/p091.pdf

These seem like they're transducers for measuring temperature. The specs list
max dissipation as 0.55W. Seems a little lightweight for an inrush limiter. I
think that they are, in this circuit, being required to dissipate much more
than that.

Is this component really appropriate in this application? With the inrush
current this amp has, I just have a hard time seeing any of these components
handling the current.

Is there a better component? A simple resistor, maybe?

Thanks,
--
DaveC
[email protected]
This is an invalid return address
Please reply in the news group

Dave,

For some good information on these devices:
http://www.thermometrics.com/assets/images/cl.pdf

Both Mouser & Digikey have them.
For Mouser:
http://www.mouser.com/
then enter current limiter in the parts search box.

For Digikey:
http://dkc3.digikey.com/PDF/T033/0821.pdf

Scroll down about 3/4 of the page - you'll see
Inrush Current Limiters. They have a wide range of values -
you'll find one suitable for your amplifier. In the absence
of any other information, select one near, (but not lower
than) the value of the fuse in your amp.

A resistor is not a suitable replacement for one of these
limiters. Also, while using a jumper, as was mentioned in
another reply, can be a good diagnostic effort, I would
recommend against leaving it in as a permanent solution.
 
D

DaveC

Jan 1, 1970
0
A resistor is not a suitable replacement for one of these
limiters. Also, while using a jumper, as was mentioned in
another reply, can be a good diagnostic effort, I would
recommend against leaving it in as a permanent solution.

Why is it not a good idea to leave it jumpered rather than replacing it with
another NTC varistor? I know the inrush current will be high, and possibly
blow the slow-blow fuse, but if I notch that up another amp or so, what's the
down side? Is this too much current for the rectifier, transformer windings,
etc., in the PS circuit?

Thanks,
 
J

James Sweet

Jan 1, 1970
0
DaveC said:
Why is it not a good idea to leave it jumpered rather than replacing it with
another NTC varistor? I know the inrush current will be high, and possibly
blow the slow-blow fuse, but if I notch that up another amp or so, what's the
down side? Is this too much current for the rectifier, transformer windings,
etc., in the PS circuit?

Yes, and to even suggest going to a higher amperage fuse to hack around this
makes me wonder if you should be poking around inside it in the first place.
Is it cheaper to burn down your house than to spend $2.50 on the right part?
 
D

DaveC

Jan 1, 1970
0
Yes, and to even suggest going to a higher amperage fuse to hack around this
makes me wonder if you should be poking around inside it in the first place.
Is it cheaper to burn down your house than to spend $2.50 on the right part?

Oh, let's not get too dramatic, here, please.

Increasing the fuse might be dangerous, but it's gonna cause whatever damage
while I'm standing right there when turn it on, not hours later.

Please don't dramatize and use fear-based logic just to make a point. People
burn down houses using extension cords for electric heaters, not by
increasing the fuse on an audio amplifier while testing it or repairing it.

But *PLEASE* let's not continue this new thread (ie, safety, etc.) here. I
want to not dilute the discussion about the NTC varistor and alternatives.

If you want to continue a discussion of whether or not you think I'm sane or
qualified to work on my own amp, start another thread or contact me off-line:
dave-univ3660ATcovadDOTnet

Thanks,
 
Top