i am puzzle by this .
if a device ( fridge , TV , washing machine , etc) is specified to be
a 240V 60Hz point , will it cause problem if it is plugged into
 a 240V 50Hz source ?
 a 220V 50Hz source
 a 220V 60Hz source
what about the case of a 240V 50Hz device connect to a 240V 60 Hz
generally , i wanted to know will it damage the device , can the house
get over-heated , etc.
 should be fine. The difference between 220v and 240v ratings is
small enough to be ignored for domestic appliances.
 and  depend very much on the type of equipment. Equipment with a
motor such as a vacuum cleaner washing machine etc may or may not run
slightly slower on 50 Hz than on 60 Hz. A digital clock or other timer
meant for 60 Hz which counts the cycles of the AC will lose time on 50
TVs and electronic equipment may well work just fine, but other
problems from the location may loom larger - 50 Hz countries tend to
use the PAL TV system, while 60 Hz countries often use NTSC. Similarly,
an FM radio or tuner may have problems with different channel spacings.
If a record player uses a
synchronous motor, it will turn at the wrong speed. If it uses a DC
motor with electronic speed control, as many do, it may be OK.
A 240v 60 Hz supply is often used in the USA for heavy current
applications such as air conditioners and cookers, and you would not
want to plug them into a 13 Amp 230v European socket, for various
reasons. You would be crazy to bring them across the Atlantic. The only
safe way to know is to contact the manufacturer.
There are motors, and there are devices like TVs that use the AC to create
their own DC power using an internal converter (power supply).
The latter usually doesn't care much about frequency, and they operate in
broad voltage ranges e.g., 100-140 volts, and 200-250 volts.
While the actual "motor engineering" can be more complicated, and there are
several kinds of motors, the basics are usually enough to get close if you
slap on a small safety factor, and they go like this:
Basically, when an engineer designs a motor or its application, he considers
primarily two things - heat and torque - and secondarily the insulation
value for voltage at heat and power. (For all intents and purposes, the
insulation voltage capacity is not a factor for most motors, but the heat
rating of the insulation is.) Power follows torque and rpm.
Heat is the result of inefficiency.
A motor can be run at any voltage and any frequency - but obviously not as
efficiently when run at a voltage and frequency other than its design
voltage and frequency. So when an engineer uses a motor, especially other
than at its rated parameters, he primarily considers that heat.
The motor puts out torque - power is torque times rpm, so a motor designed
to handle the heat from the rated power out from 50X rpm at its rated torque
may not have the capacity to handle the heat from a motor putting out 20%
more power - e.g., at 60X rpm at rated torque.
Motors designed for 60 hz operation normally have no problem handling
50hz - but because the torque available is primarily a function of the
voltage applied (which drives the amps that makes the field), then for the
same voltage, a 60 hz motor runs on 50 hz power delivers 14% less power, and
thus less heat.
(There are also motors that really don't care what the frequncy is,
because they convert the frequency internally to DC)
So you can run a motor at 120 cycles as long as you lower the voltage in
order to lower the torque and not exceed the heat capacity - that is the
basics of variable speed motor controllers
Another thing to look at is that motors respond to the load by using a
multiplicand(?) of volts and amps. For a given load, if you lower the
voltage, the amps go up.
So if you need to run the washer motor with 10 amps at 240vac, and you
lower the voltage to 220vac, it will draw 11 amps to do the same job.
And if you run a 60 hz washer at 50 hz, it will run slower.
On 28 Nov 2006 13:01:38 -0800 email@example.com wrote:
| hob wrote:
|> And if you run a 60 hz washer at 50 hz, it will run slower.|>
| Not if the motor has electronic speed control.
And how many actually have such a feature when for most sold in the markets
they are intended for would have no need for this?
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
Get up to date!
Electronic speed control has been the norm in Europe for some time, and
is becoming mainstream in the USA.
Motors are driving demand for electricity, accounting for about half of
the electricity we consume, according to the Electric Power Research
Two appliances undergoing an energy-efficiency design upgrade are
washing machines and dishwashers. While last year's worldwide washer
market-about 70 million units-grew modestly at 3.6% from the prior
the number of electronically controlled washers grew at a rate of 23%
to 15 million units,
driven by tighter standards, growing regulations, and the emergence of
the environmentally conscious consumer. To meet the need, appliance
design engineers are working hard to reduce the machine's energy
consumption, water use, weight, and cycle time, while delivering added
benefits such as better cleaning, more productive spin cycles, and
improved fabric care.
One trend in washing machine design is to replace the machine's
traditional drive system with an electronically controlled brushless
alternative. In the past, washing machine designs employed either a
two-speed single-phase ac induction motor with electromechanical
controls or a universal brushed motor with triac-switch-phase control.
The new electronic control systems are enabling features that were once
too costly or impossible to implement.
As these new features have gained popularity, manufacturers have even
begun to design them into their midrange or lower-end models.
Lower raw-material prices are making permanent-magnet synchronous (PMS)
motors more attractive than induction and universal motors, nullifying
the cost impact of electronic-component additions for the control
system. At the same time, other components have been eliminated, such
as gearboxes and pulleys required in a mechanical control scheme and
sensors needed for rotor position feedback. The results are a smaller
and lighter motor and a drive system with greater capability, higher
reliability, and improved energy efficiency.
In Europe, where I live, horizontal axis drums are the norm, and they
are catching on fast in the USA. They require fast torque response from
the controller to manage load conditions that are constantly changing.
Higher spinning speeds require better balancing of the drum to prevent
washing machine vibration, associated noise, and higher stress on
bearings and dampers.
Preventing machine wear and tear, new control systems can detect,
assess, and even predict possible out-of-balance conditions and
dynamically correct for them. The task requires high torque at low
speeds and low torque at high speeds, using artificial field weakening.
Drum-spinning speed itself has become a significant design
consideration and important product differentiator. Today's European
washing machines advertise spinning speeds of up to 2,000 rpm.
With variable-speed motor control systems in place, washing programs
can be expanded to accommodate previously nonwashable fabrics and
protect the environment further by reducing the amount of detergent
required. A final trend, found at the core of variable-speed motion
control systems, is the move to sinusoidal drive schemes to minimize
That long? I didn't realise, although i can believe it. I used to work
in the UK for a charity which reconditioned unwanted washing machines
and either gave or sold them at low prices to people on benefits, and
the guy who did the reconditioning work told me that "these days"
(around 1990) all the broken washing machines we got donated seemed to
have circuit boards for motor control. Not like the old days when it
was all contactors and split windings. He built up a stock of working
modules from machines which were deemed unsuitable for reconditioning
for various reasons such as corroded casings. We used about 6 main
brands and a surprising amount of stuff was common.
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