Rectifier output?

[Eeyore]

John Larkin wrote:

On Wed, 23 Sep 2009 20:12:47 -0700, Gloria West
gloriasbest22@NOSPAMgmail.com> wrote:

120vac input to full-wave rectifier bridge. Without any filtering components
what is the output RMS voltage?

About 119.

Surely very slightly less, e.g. 118.5 due to 2 x Vf of the diodes in the
bridge but without If being specified and the specific diodes, hard to
be exact ?

Graham

 

[John Fields]

On Fri, 25 Sep 2009 05:42:36 +0100, Eeyore
<rabbitsfriendsandrelations@removethishotmail.com> wrote:

John Larkin wrote:
On Wed, 23 Sep 2009 20:12:47 -0700, Gloria West
gloriasbest22@NOSPAMgmail.com> wrote:

120vac input to full-wave rectifier bridge. Without any filtering components
what is the output RMS voltage?

About 119.

Surely very slightly less, e.g. 118.5 due to 2 x Vf of the diodes in the
bridge but without If being specified and the specific diodes, hard to
be exact ?

---
What is it you don't understand about 'about'?

 

[Phil Allison]

"Ross Herbert"

The relays, presumably, did not "buzz" when the system was first designed.
Unless the spring loading on the armature has been increased then the
relay
should not buzz when driven from a non-filtered bridge rectifier output.
Since
the mains input period is 16.7ms there is only a very brief period
(somewhere in
the region of 3-5ms) between the 8.35ms half cycles when the voltage will
be
reduced below the holding voltage of the relay and the normal magnetic
inertia
of the magnet system should be sufficient to keep the armature from
chattering.

** Just tried a couple of 48 volt relays: a Finder octal base type (DPDT
10A)
and an Omron PCB mount ( SPDT 16A) miniature.

Both worked just fine with full wave rectified, 50Hz AC.

Both closed with just 30 volts rms supplied via a bridge rectifier = 26
volts DC average on the coil.

NO TRACE OF BUZZING NOISE WHATSOEVER !!

However:

With half wave rectification, both relays buzzed loudly and would not close
at any voltage

Conclusion:

The OP simply has a faulty bridge rectifier.


BTW:

110 volt DC relays are apparently designed to work from rectified US mains
with no filtering.



...... Phil

 

[John Fields]

On Wed, 23 Sep 2009 23:05:35 -0700, Gloria West
<gloriasbest22@NOSPAMgmail.com> wrote:

120vac input to full-wave rectifier bridge. Without any filtering components
what is the output RMS voltage?

This does not use a center-tapped transformer or such.

Relays run with this rectified supply are buzzing. These are in a 45-year-old
printing press.

I want to replace them with something more modern (the contacts are also
intermittent).

I found some that are rated for 110 dc:

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-
1&storeId=10001&catalogId=10001&productId=301209&

Will these buzz also? Is there a simple way to keep them quiet?

---
I have a P&B KR3DH with a 110VDC coil which is identical to the one you
posted a link to, and it doesn't buzz when driven with full-wave
rectified 120VRMS at 60Hz.

It pulls in at 76VRMS, drops out at 32VRMS, and buzzes a little for
maybe 1/2 second at the pickup and release points, but pulls in fully or
drops out fully after that anyway.

Switching it on and off though, instead of gradually increasing or
decreasing the coil voltage results in a nice clean on and off snap.


JF

 

[Speeders & Drunk Drivers]

"John Fields" <jfields@austininstruments.com> wrote in message newsnfpb5psgv1khjc0p5c0r1v80f10e3u0k5@4ax.com...

On Fri, 25 Sep 2009 05:42:36 +0100, Eeyore
rabbitsfriendsandrelations@removethishotmail.com> wrote:

John Larkin wrote:
On Wed, 23 Sep 2009 20:12:47 -0700, Gloria West
gloriasbest22@NOSPAMgmail.com> wrote:

120vac input to full-wave rectifier bridge. Without any filtering components
what is the output RMS voltage?

About 119.

Surely very slightly less, e.g. 118.5 due to 2 x Vf of the diodes in the
bridge but without If being specified and the specific diodes, hard to
be exact ?

---
What is it you don't understand about 'about'?

Outch! Graham (the wanna-be scientist) got kicked out again by John Fool....Heehee........

 

[John Fields]

On Fri, 25 Sep 2009 11:48:48 -0700, "Speeders & Drunk Drivers are
MURDERERS" <xeton2001@yahoo.com> wrote:

Outch! Graham (the wanna-be scientist) got kicked out again by John Fool....Heehee........

---
What are you doing back?

Need some more slappin' around?

 

[Speeders & Drunk Drivers]

"Phil Allison" <phil_a@tpg.com.au> wrote in message news:7i070hF2v7pk9U1@mid.individual.net...

"Gloria West"

120vac input to full-wave rectifier bridge. Without any filtering
components
what is the output RMS voltage?


** 120 volts, of course.

If you connect a 120 volt lamp to the DC output, it will be the same
brightness as usual.

If you add a filter capacitor, the rms voltage rises up to a maximum of 170
volts DC.



..... Phil

Depending on the value of your capacitor of course! Don't assume too high automatically.......Heehee..........

 

[Speeders & Drunk Drivers]

"John Fields" <jfields@austininstruments.com> wrote in message news:174qb59of5agaq0go9ls4t07ii1jbs88pd@4ax.com...

On Fri, 25 Sep 2009 11:48:48 -0700, "Speeders & Drunk Drivers are
MURDERERS" <xeton2001@yahoo.com> wrote:


Outch! Graham (the wanna-be scientist) got kicked out again by John Fool....Heehee........

---
What are you doing back?

Need some more slappin' around?

Heeehee....You think so hugh dumbass?

 

[Speeders & Drunk Drivers]

"Gloria West" <gloriasbest22@NOSPAMgmail.com> wrote in message news:0001HW.C6E100E202BBDA06B08A39AF@news.eternal-september.org...

Add a 4.7uF, 250 volt electro across the output of the bridge and put a 4700
ohm, 1 watt resistor in series with the 110 volt relay.

Thank you Phil.

Don't believe in every formula you see on the internet, or on a simulated software. The original Ohm's Law works better. 4.7uF to raise voltage to 160V DC? Wow! sounds too far off, unless the designer doesn't have to have any load on it but then why design something without load right?

 

[John Fields]

On Fri, 25 Sep 2009 12:00:05 -0700, "Speeders & Drunk Drivers are
MURDERERS" <xeton2001@yahoo.com> wrote:

"John Fields" <jfields@austininstruments.com> wrote in message news:174qb59of5agaq0go9ls4t07ii1jbs88pd@4ax.com...
On Fri, 25 Sep 2009 11:48:48 -0700, "Speeders & Drunk Drivers are
MURDERERS" <xeton2001@yahoo.com> wrote:


Outch! Graham (the wanna-be scientist) got kicked out again by John Fool....Heehee........

---
What are you doing back?

Need some more slappin' around?


Heeehee....You think so hugh dumbass?

---
"Hugh", dumbass?

 

[John Fields]

On Fri, 25 Sep 2009 12:03:55 -0700, "Speeders & Drunk Drivers are
MURDERERS" <xeton2001@yahoo.com> wrote:

"Gloria West" <gloriasbest22@NOSPAMgmail.com> wrote in message news:0001HW.C6E100E202BBDA06B08A39AF@news.eternal-september.org...
Add a 4.7uF, 250 volt electro across the output of the bridge and put a 4700
ohm, 1 watt resistor in series with the 110 volt relay.

Thank you Phil.




Don't believe in every formula you see on the internet, or on a simulated software.
The original Ohm's Law works better. 4.7uF to raise voltage to 160V DC?
Wow! sounds too far off, unless the designer doesn't have to have any load on it
but then why design something without load right?

---
How would you use Ohm's law to determine the voltage a capacitor would
charge to from a rectified AC source?

And fix your line wrap, moron.

 

[Baron]

John Fields wrote:

On Fri, 25 Sep 2009 12:00:05 -0700, "Speeders & Drunk Drivers are
MURDERERS" <xeton2001@yahoo.com> wrote:


"John Fields" <jfields@austininstruments.com> wrote in message
news:174qb59of5agaq0go9ls4t07ii1jbs88pd@4ax.com...
On Fri, 25 Sep 2009 11:48:48 -0700, "Speeders & Drunk Drivers are
MURDERERS" <xeton2001@yahoo.com> wrote:


Outch! Graham (the wanna-be scientist) got kicked out again by John
Fool....Heehee........

---
What are you doing back?

Need some more slappin' around?


Heeehee....You think so hugh dumbass?

---
"Hugh", dumbass?

He can't speel either !

--
Best Regards:
Baron.

 

[Ross Herbert]

On Fri, 25 Sep 2009 23:31:58 +1000, "Phil Allison" <phil_a@tpg.com.au> wrote:

:
:"Ross Herbert"
:>
:> The relays, presumably, did not "buzz" when the system was first designed.
:> Unless the spring loading on the armature has been increased then the
:> relay
:> should not buzz when driven from a non-filtered bridge rectifier output.
:> Since
:> the mains input period is 16.7ms there is only a very brief period
:> (somewhere in
:> the region of 3-5ms) between the 8.35ms half cycles when the voltage will
:> be
:> reduced below the holding voltage of the relay and the normal magnetic
:> inertia
:> of the magnet system should be sufficient to keep the armature from
:> chattering.
:
:
:** Just tried a couple of 48 volt relays: a Finder octal base type (DPDT
:10A)
:and an Omron PCB mount ( SPDT 16A) miniature.
:
:Both worked just fine with full wave rectified, 50Hz AC.
:
:Both closed with just 30 volts rms supplied via a bridge rectifier = 26
:volts DC average on the coil.
:
:NO TRACE OF BUZZING NOISE WHATSOEVER !!
:
:However:
:
:With half wave rectification, both relays buzzed loudly and would not close
:at any voltage
:
:Conclusion:
:
:The OP simply has a faulty bridge rectifier.
:
:
:BTW:
:
:110 volt DC relays are apparently designed to work from rectified US mains
:with no filtering.
:
:
:
:..... Phil
:
:
:

Thanks for confirming my hypothesis Phil. I concur the most likely reason for
the OP's buzzing relay may be a faulty diode in the bridge.