"Dave Platt" wrote in message
...
When I dare to use an
A) electric blanket, or a electric frying pan set on "low",
at the same time when there is a
B) UPS computer power supply, or Ham radio power supply
also turned on anywhere in the house, the power supplies hum most
worryingly. One must make a choice: A) food, warmth, or B) fun.

What is the name of this waveform resonance with the current limiters
of A phenomena? Is there some kind of filter I can apply?

That sounds to me as if you're running into a "harmonic currents"
issue. This occurs if you have something connected to the mains which
draws current in a nonlinear fashion (i.e. current drawn is not
linearly related to the instantaneous value of the voltage sinusoid).

In my experience, the commonest cause for this is a device which uses
a triac "chopper" to control the amount of current being used. Such
devices "switch on" partway through each powerline cycle (120 times a
second), so the current jumps from zero to a fairly high value. The
sudden jump creates a load on the line with frequency components at
harmonics of the 60 Hz powerline frequency... hence the name.

The devices you indicate (electric blankets, frying pans), and light
dimmers are notorious culprits.

Some of these devices may draw current in an asymmetrical fashion...
e.g. they might use a half-wave rectifier diode, and thus draw current
on only the positive half of the AC cycle and not on the negative (or
vice versa). "Light bulb saver" discs (little disc-shaped diodes that
go into a light socket before the bulb) do this. In effect, the
asymmetrical load creates a DC offset on the voltage "seen" by other
devices on the same circuit.

All of these "bad loads" can cause transformers in other devices to
start humming or buzzing. Toroidal power transformers are
particularly subject to buzzing if there's an asymmetrical load / DC
offset on the line.

I don't know of any good way of filtering out this sort of problem...
an isolation transformer can help somewhat, sometimes, but it's an
expensive solution and I don't think it's very effective.

If you've got really severe humming/buzzing with something as simple
and low-wattage as an electric blanket, , I'd be a bit concerned
that this might indicate that there's a problem in your house
wiring... overloaded circuits, a bad or loose connection somewhere, or
even a loose or open neutral. The latter is a dangerous situation.
If you should notice lights getting brighter, or appliance motors
speed up, when you turn *on* a light or appliance elsewhere in the
house... then you may have an open neutral and should call the power
company immediately. I've had this happen twice (squirrel chewed
through the neutral wire in our building's drop from the pole
transformer), and PG&E always reacted immediately... their dispatcher
said that they consider a "low voltage / high voltage" situation to
require immediate action.

You might want to have an electrician check out your house wiring.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!


cut the ground off the blanket that will make the hum go away

In article ,
KC8QJP wrote:

cut the ground off the blanket that will make the hum go away

That strikes me as very poor advice, for three reasons:

[1] I've never seen an electric blanket or bed-heating pad here in the
U.S. which *has* a ground prong. They all use two-wire
(hot/neutral) plugs.

[2] If there *is* a ground prong on a device which is used in close
proximity to a human body, it's probably there for a very good
reason (safety). Removing a safety ground from such a device
seems like a really bad idea.

[3] If the reason for the humming is a harmonic-currents problem (as I
suspect) then it has *nothing* to do with the presence or absence
of a ground connection. It's due to irregular current flows on
the hot and neutral wires. Floating the device free from the
safety ground will have not reduce the problem at all.

"Floating" an equipment-chassis ground can sometimes help reduce hum
in audio/video equipment if the hum is due to a ground loop. I don't
believe that ground loops have anything at all to do with the original
poster's buzzing-transformer problem.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

DP [1] I've never seen an electric blanket or bed-heating pad here in
DP the U.S. which *has* a ground prong.
No ground prong on my blanket or frying pan.
Thick house wiring all done by myself, so that can't be the problem
(don't tell Mom about the day I made a loop and all the conduits in
the walls shook.)
Therefore I shall, as a nod to the less privileged who perhaps don't
even have electric power, learn not to eat or sleep while using the
computer or my radio equipment (BM4IFV, not on air anymore, now just
on email). OK, thanks. Bye.

On Jan 4, 10:40*am, "KC8QJP" wrote:
"Dave Platt" wrote in message

...



When I dare to use an
A) electric blanket, or a electric frying pan set on "low",
at the same time when there is a
B) UPS computer power supply, or Ham radio power supply
also turned on anywhere in the house, the power supplies hum most
worryingly. One must make a choice: A) food, warmth, or B) fun.

What is the name of this waveform resonance with the current limiters
of A phenomena? Is there some kind of filter I can apply?

That sounds to me as if you're running into a "harmonic currents"
issue. *This occurs if you have something connected to the mains which
draws current in a nonlinear fashion (i.e. current drawn is not
linearly related to the instantaneous value of the voltage sinusoid).

In my experience, the commonest cause for this is a device which uses
a triac "chopper" to control the amount of current being used. *Such
devices "switch on" partway through each powerline cycle (120 times a
second), so the current jumps from zero to a fairly high value. *The
sudden jump creates a load on the line with frequency components at
harmonics of the 60 Hz powerline frequency... hence the name.

The devices you indicate (electric blankets, frying pans), and light
dimmers are notorious culprits.

Some of these devices may draw current in an asymmetrical fashion...
e.g. they might use a half-wave rectifier diode, and thus draw current
on only the positive half of the AC cycle and not on the negative (or
vice versa). *"Light bulb saver" discs (little disc-shaped diodes that
go into a light socket before the bulb) do this. *In effect, the
asymmetrical load creates a DC offset on the voltage "seen" by other
devices on the same circuit.

All of these "bad loads" can cause transformers in other devices to
start humming or buzzing. *Toroidal power transformers are
particularly subject to buzzing if there's an asymmetrical load / DC
offset on the line.

I don't know of any good way of filtering out this sort of problem...
an isolation transformer can help somewhat, sometimes, but it's an
expensive solution and I don't think it's very effective.

If you've got really severe humming/buzzing with something as simple
and low-wattage as an electric blanket, , I'd be a bit concerned
that this might indicate that there's a problem in your house
wiring... overloaded circuits, a bad or loose connection somewhere, or
even a loose or open neutral. *The latter is a dangerous situation.
If you should notice lights getting brighter, or appliance motors
speed up, when you turn *on* a light or appliance elsewhere in the
house... then you may have an open neutral and should call the power
company immediately. *I've had this happen twice (squirrel chewed
through the neutral wire in our building's drop from the pole
transformer), and PG&E always reacted immediately... their dispatcher
said that they consider a "low voltage / high voltage" situation to
require immediate action.

You might want to have an electrician check out your house wiring.

--
Dave Platt * * * * * * * * * * * * * * * * * AE6EO
Friends of Jade Warrior home page: *http://www.radagast.org/jade-warrior
*I do _not_ wish to receive unsolicited commercial email, and I will
* * boycott any company which has the gall to send me such ads!

cut the ground off the blanket that will make the hum go away- Hide quoted text -

- Show quoted text -

impostor

A measure recently taken that will have repercussions that will
indicate exactly how severely your actions have impacted upon fellow
keyclowns.

This measure was taken in your honor. You'll be hearing about it, but
not from us.

wrote in message
...
On Jan 4, 10:40 am, "KC8QJP" wrote:
"Dave Platt" wrote in message

...



When I dare to use an
A) electric blanket, or a electric frying pan set on "low",
at the same time when there is a
B) UPS computer power supply, or Ham radio power supply
also turned on anywhere in the house, the power supplies hum most
worryingly. One must make a choice: A) food, warmth, or B) fun.

What is the name of this waveform resonance with the current limiters
of A phenomena? Is there some kind of filter I can apply?

That sounds to me as if you're running into a "harmonic currents"
issue. This occurs if you have something connected to the mains which
draws current in a nonlinear fashion (i.e. current drawn is not
linearly related to the instantaneous value of the voltage sinusoid).

In my experience, the commonest cause for this is a device which uses
a triac "chopper" to control the amount of current being used. Such
devices "switch on" partway through each powerline cycle (120 times a
second), so the current jumps from zero to a fairly high value. The
sudden jump creates a load on the line with frequency components at
harmonics of the 60 Hz powerline frequency... hence the name.

The devices you indicate (electric blankets, frying pans), and light
dimmers are notorious culprits.

Some of these devices may draw current in an asymmetrical fashion...
e.g. they might use a half-wave rectifier diode, and thus draw current
on only the positive half of the AC cycle and not on the negative (or
vice versa). "Light bulb saver" discs (little disc-shaped diodes that
go into a light socket before the bulb) do this. In effect, the
asymmetrical load creates a DC offset on the voltage "seen" by other
devices on the same circuit.

All of these "bad loads" can cause transformers in other devices to
start humming or buzzing. Toroidal power transformers are
particularly subject to buzzing if there's an asymmetrical load / DC
offset on the line.

I don't know of any good way of filtering out this sort of problem...
an isolation transformer can help somewhat, sometimes, but it's an
expensive solution and I don't think it's very effective.

If you've got really severe humming/buzzing with something as simple
and low-wattage as an electric blanket, , I'd be a bit concerned
that this might indicate that there's a problem in your house
wiring... overloaded circuits, a bad or loose connection somewhere, or
even a loose or open neutral. The latter is a dangerous situation.
If you should notice lights getting brighter, or appliance motors
speed up, when you turn *on* a light or appliance elsewhere in the
house... then you may have an open neutral and should call the power
company immediately. I've had this happen twice (squirrel chewed
through the neutral wire in our building's drop from the pole
transformer), and PG&E always reacted immediately... their dispatcher
said that they consider a "low voltage / high voltage" situation to
require immediate action.

You might want to have an electrician check out your house wiring.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

cut the ground off the blanket that will make the hum go away- Hide quoted
text -

- Show quoted text -



A measure recently taken that will have repercussions that will
indicate exactly how severely your actions have impacted upon fellow
keyclowns.

This measure was taken in your honor. You'll be hearing about it, but
not from us.


http://www.google.com/search?hl=en&q...earch&aq=f&oq=

UH OH KC8QJP IS IN EVEN MORE TROUBLE????
CRISCO KATHY BETTER WISE UP ALREADY!!!!