Why 60 hertz or 50hert

[[email protected]]

Many long distance feeds are now HVDC, which deals with the frequency
difference problem just fine.

I believe parts of Japan are 50 Hz and other parts are 60.

I've never heard about 30 Hz, but the swedish railroads use 16 2/3 Hz
(50/3) for the trains. The store behind this was that that was such a
low frequency that they could use DC motors in the early electrical
locomotives.

I live by the railroad, and when I was using a CRT monitor I could see
when a train approached from the north, as the current to drive the
train induced a strong magnetic field at 16 2/3 Hz, and the picture
would wobble slightly.

Dc motors wont work on ac of any frequency. Low frequencies used in
traction improve the motors' starting torque, and of course this is
important.

I've got a very old domestic appliance that claims to handle 25Hz, but
where 25Hz was ever found in homes in UK I dont know. I wonder if a few
old private gen plants used it at the time, and they thought theyd
corner the market, but am far from convinced.


NT

 

[Peter Dettmann]

Dc motors wont work on ac of any frequency. Low frequencies used in
traction improve the motors' starting torque, and of course this is
important.

I've got a very old domestic appliance that claims to handle 25Hz, but
where 25Hz was ever found in homes in UK I dont know. I wonder if a few
old private gen plants used it at the time, and they thought theyd
corner the market, but am far from convinced.


NT

You did not mention what appliance it was that was rated also for
25hz, but all toasters, and radiators would easily be included in the
list, and these would also work on the ultimate low frequency (DC).

Although 25 Hz was mostly used for trains, a lot of railway housing
and stations were also using this frequency (seeing it was readily
available). And you could see the flicker in the lighting where 25Hz
was used.

Peter Dettmann

 

[Homer J Simpson]

Dc motors wont work on ac of any frequency.

Not necessarily true. Clearly they work on ZF, and would continue to work
until the motor impedance became significant.

 

[Michael A. Terrell]

30 ?

Where ?

Graham

Actually, it was 25 Hz and it was used in areas around mines.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Thomas Tornblom]

Dc motors wont work on ac of any frequency.

Well, that depends on the type of DC motor, doesn't it?

There are motors that work just fine on either AC or DC.

Here's an article that agrees with what I said:
http://www.bueker.net/trainspotting/voltage_sixteentwothirds.php

 

[[email protected]]

[email protected] writes:

Well, that depends on the type of DC motor, doesn't it?

There are motors that work just fine on either AC or DC.

then they arent dc motors. Not often one has to state something quite
that obvious.


NT

 

[[email protected]]

Not necessarily true. Clearly they work on ZF,
yes

and would continue to work
until the motor impedance became significant.

no. A dc motor is by definition one that runs on dc only. Typically
these are permanent magnet motors, in which direction of rotation
depends on polarity. Motor impedance is not the issue. Motor impedance
is the issue with universal or ac/dc motors.


NT

 

[Steven Swift]

Dc motors wont work on ac of any frequency. Low frequencies used in
traction improve the motors' starting torque, and of course this is
important.

Not quite true. Series wound DC motors (often called "universal" motors)
work on AC and DC. Frequency is a don't care. Often used in cheap appliances,
like mixers or hair dryers.

Steve.

 

[Thomas Tornblom]

Not quite true. Series wound DC motors (often called "universal" motors)
work on AC and DC. Frequency is a don't care. Often used in cheap appliances,
like mixers or hair dryers.

Engine starters are also frequently of this type. Perhaps less now
with permanent magnet gear starters.

Steve.

Thomas

 

[Homer J Simpson]

no. A dc motor is by definition one that runs on dc only. Typically
these are permanent magnet motors, in which direction of rotation
depends on polarity. Motor impedance is not the issue. Motor impedance
is the issue with universal or ac/dc motors.

Nope. I doubt anyone has EVER built a traction motor with permanent magnets.

 

[Homer J Simpson]

then they arent dc motors. Not often one has to state something quite
that obvious.

And yet they are called AC/DC motors. And run on either. Seems you need to
take a course - or two - before correcting others.

 

[Michael A. Terrell]

Suppliers to the world market usually design for 50/60 Hz since 60Hz use is
quite rare on the global scale of things.

60Hz only transformers tend to be the speciality of the USA.

Still trolling? Sci.electronics.design not big enough for all your
nonsense? What transformers are you talking about? Those cheap,
imported Chinese wall warts, or pole pigs? Just about everything else
is built with a SMPS. Why waste both iron and copper to build 50 Hz
transformers for the domestic market?

You just can't wait to get in another of your anti America digs, can
you?


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[[email protected]]

And yet they are called AC/DC motors. And run on either.

precisely, not dc motors.


NT

 

[[email protected]]

Yeah, imagine having to make parts of niagara falls flow at
different rates to accommodate the two standards.

How do you think they control the frequency? They adjust the water
flow through the turbines to get the required speed. They have to match
the speed and phase of the grid before they can connect, then they
increase the water flow till the generator is producing the desired
current.

It would be very easy to change the speed, but it would make more
sense to use an alternator designed for the desired frequency.

 

[CJT]

How do you think they control the frequency? They adjust the water
flow through the turbines to get the required speed. They have to match
the speed and phase of the grid before they can connect, then they
increase the water flow till the generator is producing the desired
current.

It would be very easy to change the speed, but it would make more
sense to use an alternator designed for the desired frequency.

.... which one would then need to run at the correct speed.

 

[Homer J Simpson]

[email protected] wrote:
... which one would then need to run at the correct speed.

And it is (or was) the practice to run an AC clock off the output and trim
the speed to keep it at the correct time using another reference. That way
all of the AC clocks in town would stay in time.