On Sun, 06 Oct 2019 06:02:46 +0100, AlexK wrote:



"Commander Kinsey" wrote in message
news
On Sun, 06 Oct 2019 00:05:40 +0100, AlexK wrote:



"Commander Kinsey" wrote in message
news On Sat, 05 Oct 2019 22:15:34 +0100, AlexK wrote:



"Commander Kinsey" wrote in message
news On Sat, 05 Oct 2019 21:17:00 +0100, AlexK wrote:



"Commander Kinsey" wrote in message
news On Fri, 04 Oct 2019 23:46:55 +0100, AlexK wrote:



"Commander Kinsey" wrote in message
news On Fri, 04 Oct 2019 19:17:46 +0100, AlexK wrote:



"Commander Kinsey" wrote in message
news On Fri, 04 Oct 2019 09:41:25 +0100, PeterC

wrote:

On Thu, 3 Oct 2019 19:29:42 +0100, Robert wrote:

On 03/10/2019 14:29, Commander Kinsey wrote:
Why do LEDs generate heat? I want a technical answer not
"because
they're inefficient". And will we ever make them more
efficient?
Besides the inefficiencies in the LED itself which other
posters
have
covered, LED lamps have some current regulation or power
supply
built-in
which will not be 100% efficient and thus generates heat.

If my meter is correct, all the LEDs that I've measured have a
PF
of
approx.
0.5 - not a good start.
One TV has a PF of 0.97 and is barely warm over the PSU;
another
is
0.86
and
is luke warm. The real warmth in the 2nd. one is around the
inputs
though -
SPDIF, USB and HDMI.

Is power factor that important? In a domestic building, you are
not
billed for power factor. I might have a capacitive load, but my
neighbour
has an inductive load, so they even out.

Most neighbours don't have much long term inductive load anymore.

I don't see why it would have reduced.

It has anyway.

For what reason

To get better motors, direct drive etc with washing machines for
example.

What has direct drive got to do with power factor?

They arent the old induction motors with the power factor they had.

I thought all motors created the same inductive load,

But not necessarily on the mains, that's what matters
with the more sophisticated motors used in stuff like
washing machines etc now.

Are they fed by altered AC or by DC?

They arent on the mains. They are driven by the electronics.
Similar to the difference between a conventional transformered
power supply and a modern switch mode power supply instead.

I know they don't get driven directly from the mains, as they need to go different speeds. But are they DC or AC? since they can rotate either way, does that mean they have to be DC? Or can it be AC using different coils?

and had to be compensated for if you wanted unity PF.

There is no point in the cost of doing that with domestic appliances.

I know, I just thought that was the only way to remove the PF of any
motor.

The other obvious way is to drive it with the electronics
instead of having it on the mains. Most obviously with
a stepper motor, although that isnt what is used in
washing machines.

Depends what the electronics is as to whether it blocks the PF?

Direct drive motors are interesting - I once had a very cheap
turntable
that said "direct drive", so I guess it's not always a good thing?

There's a big difference between a turntable motor and
one in a top loading washing machine which needs to
do a variety of different things when washing, adjitating
and spin drying at different speeds.

I know. Which makes me think it's important for a washing machine. But
on a turntable, it has to be a very precise speed or the music sounds
****. It's the last place I'd think of putting one.

Its done with those to avoid belts and the downsides with those over
time.

I had a Garrard turntable that was decades old and I think that was belt
drive.

Yes, the early ones did, before power semiconductors
were economically feasible for that sort of situation.

I think this one was from the 60s or earlier.

Although it never went wrong so I never had cause to look inside.

Actually I think I remembered wrong, the cheap stereo might have said
"belt drive" on the front. Direct drive could have been the decent one.

Very likely.

From Wikipedia: "Usually motors are built to achieve maximum torque at
high rotational speeds, usually 1500 or 3000 rpm."
I thought motors produced more torque when slower - which is why they
burn out when jammed.

Not relevant to what is being discussed, the power factor.

Aren't I allowed to drift the conversation a little?

Nope, the death squad has its orders...

I don't take orders from convicts :-)

It's the death squad that has its orders, not you.

[facepalm]