# How frequency effects voltage

Discussion in 'Electronic Basics' started by [email protected], Dec 27, 2005.

1. ### Guest

I mean why we use 50/60 Hertz in houses why we dont use 400Hertz. i
know as we increase frequency losses increase but what is formula or
equation for that.

2. ### Tom BiasiGuest

Unfortunately not every problem is solved by plugging numbers into a
formula.
Your question is a good one but you need to do some studying on the way
higher frequency AC behaves in transmission lines and in every day inductors
like drills, mixers, etc.
You may find some interest in Edison's proposal to feed the world power with
DC and what some rebuttals to this entailed.
Good question, take a fun journey.
Regards,
Tom

3. ### John PopelishGuest

There are quite a few different factors to consider when deciding on
the "best" power distribution frequency. In general, the transformer
core size goes up proportional to the inverse of the frequency. So
400 Hz transformers are about 60/400=15% the size of those for 60 Hz.
This is an economic advantage for the higher frequency. But the
core loss goes up as the frequency does, in two ways. There are eddy
current losses (current that circulates in the core as if it were a
short circuited transformer secondary) that can be reduced by making
the laminations of higher resistivity material (most commonly, by
alloying silicon with iron) and by making it of stacks of insulated
laminations that are proportionately thinner.

There are also per cycle losses related to the energy lost each time
you reverse the direction of magnetization in iron, called hysteresis
losses. There is nothing you can do about those, as long as you use
iron for the core material. The exotic core materials with much lower
hysteresis losses are a lot more expensive than the silicon iron alloy
used for 60 Hz transformers.

There is also the problem of phase shifts over distance that gets
worse in proportion to the frequency. A wavelength at 60 Hz is
something like 3100 miles. At 400 Hz, that drops to about 470 miles.
You get into huge problems trying to connect a vast network of
generators and consumers with transmission lines when there are waves
of many phases propagating around all possible loops of the system,
some places aiding and some places canceling (called standing waves).
This makes it almost impossible to build a system with multiple
redundant energy paths, to handle all sorts of load shifts and
equipment failures. In effect, each state or city would have to have
its own independent 400 Hz grid.

I think those are the biggest factors in favor of lower frequency
transmission of power. There are quite a few more second and third
order factors, some of which may have applied more at the origin of
the grid than they might, now, with advances in technology.

4. ### pebeGuest

Tom Biasiwrote
formula
Your question is a good one but you need to do some studying on th
way
higher frequency AC behaves in transmission lines and in every da
inductors
like drills, mixers, etc
You may find some interest in Edison's proposal to feed the worl
power with
DC and what some rebuttals to this entailed
Good question, take a fun journey
Regards
Tom[/quote:dafa126be6
Just a passing thought about Edison's world power feeds. There ar
instances now where high voltage is being carried as DC on the grid
It is used where countries with different frequency standards consum
each other's electricity, and because it is now becoming cos
effective because for a given maximum voltage, DC can carry about 40
more power than AC of the same peak voltage

5. ### John LarkinGuest

Motors. A 24,000 RPM induction motor would be hard to handle.

John

6. ### Sjouke BurryGuest

Have worked in a place with 400Hz(military complex), wel you
wont like it . The facility was drenched in audible harmonics,
1200 Hz (3rd harmonic) being particulary audible.
People working there for 10+ years had permanent damage in
their hearing curve, and did not hear that frequency anymore.
So no, dont do it.

7. ### Bill GrayGuest

Why does the military use 400Hz?

Bill,
Phoenix

8. ### Ralph MoweryGuest

To save weight , especially in the aircraft.
Sometimes on the stuff that has to be carried on the backs of the ground
forces.

9. ### Sjouke BurryGuest

Airforce facility, airforce equipment, and a bit of stupidity
perhaps?? They had a huge flywheel/moto/dynamo/diesel running
for conversion and emergency power.

10. ### Pooh BearGuest

Generators too !

Graham

11. ### John PopelishGuest

But also very useful for some applications.
You can make them run slower at the cost of more poles.

12. ### John LarkinGuest

But all the transformers up on the poles would go

hhhhmmmmmmmmmmmmmmmmmmmm...

John

13. ### John PopelishGuest

They do that now. At 400 Hz they go WHEEEEEEEEEEEEEEEE.

14. ### Rheilly PhoullGuest

That would be hard to take, having the distribution trannys "Whee"ing all
over folks !!

15. ### Rich GriseGuest

Airplanes.

The transformers are smaller, and the engine usually revs so high
that generating 400Hz is trivial.

I _have_ always wondered, though, if they really have that box of
dirt in the tail section for "ground". ;-P

Cheers!
Rich

16. ### Guest

There is no as such the equation for frequency effect on domestic
distribution system. But yes, if we are going to use the devices which
differ form power frequency ( 50 Hz) at rated voltages ( 230 / 240
Volts), then this will unnecessarily heat up the core of electric
machines ( viz Motors, compressors of refrigerators, COres of
transformers used in that circle etc).As far as usage of electronic
devices is concerend since they are of relatively low power level, the
effect would not be significant.

Hope it is clear.

M.S.Chaitanya.

17. ### krishnaGuest

Hi list,
I think the electronics part of ur reply is not valid MR.
Chaitanya.Actually the components of any ckt(electrical/electronic)
have a tolerance limit.The rate at which they can react to application
of voltages or rate of change of current across them.Hence almost all
the components that are currently designed for 50/60hz would choke down
and hence most of the ckts simply won't react so fast.Resulting in very
fast friction at molecular level,and hence huge amt of heat
dessipation.Hence we need to redesign our ckts.Hope the answer was
clear.