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Voltage Stabilisers and Regulators

Electric Motors, Coils, Voltage Stabilisers or Regulators

A Voltage Stabiliser can be very useful for preventing damage to expensive or delicate electrical or electronic equipment. They can correct the voltage of your electricity supply if for some reason it rises or falls from the standard. Good stabilisers will cut off the electricity supply if the voltage rises or falls too to be corrected by the stabiliser. A Voltage stabiliser is a type of transformer that is able to adjust itself. Here we look at the development of transformers and how they are used to regulate or stabilise the voltage in your electrical circuits.

See the full Fixed Abode article "Danish Bacon" here.

The relationship between electricity and magnetism

Let us start by looking at the relationship between electricity and magnetism and how this lead to the invention of electric motors and transformers which is the basis for how we can regulate or stablise the voltage in our electrical supply.

In 1820 Hans Christian Orsted first discovered the close relationship between electricity and magnetism.

He found that if you connect a wire to a battery and electricity flows through the wire it creates magnetism that flows around the wire. The magnetic field flows either clockwise or anticlockwise depending on which way the electricity is flowing.

Electric copper coils

If we get a long piece of bare copper wire and wind it many times around a cardboard tube we can make a copper coil. If we now connect our coil to a battery we find we have a magnetic field running through the tube. Now if we put a piece of iron inside the tube and we switch on the electric current the iron will be forced out of the tube.

It was Hans Christian Orsted's observations that helped us to understand the basic phenomenon linking electricity, magnetism and moving pieces of iron which is, of course, the basis of the majority of electrical applications we use in our daily lives.

The basis for the electric motor

By rotating a coil of copper wire in a magnetic field we generate electricity in power stations, motor car alternators, generators, windmills, etc. By using electricity to flow through a copper coil we generate a magnetic field and move iron which makes an electric motor turn to drive our water pump, air conditioner, vacuum cleaner. In the same way we can make the middle of a loudspeaker move backwards and forwards to play Beethoven's 1812 overture.

Our lives are surrounded by dozens of copper coils carrying electricity to produce magnetic fields and make our lives easier.

There is another very common use for copper coils and magnetic fields.

Electricity providers provide us with standard electricity supplies and these have to be very stable or they will damage fragile electronic equipment. the supply should have a fixed voltage of 110 volts in America, 240 volts in Britain and 220 volts in Indonesia.


Many appliance in our lives don't want 220 volts, electronic equipment tends to require only a few volts. We use a transformer to reduce the voltage.

We talked above about a coil of copper wire to produce a magnetic field. Now if we make a second coil of wire and we put it into the same magnetic field (we can wind it over the top of the first coil) we will find that when we put electricity into the first coil, this will generate a magnetic field which in turn will 'induce' electricity in the second coil.

Now comes the clever part, if the second coil is exactly the same as the first we will get the same voltage coming out as we have going in but, if we change the second coil (we might make the wire thicker or make it longer or shorter) we will get a different voltage coming out. If the second coil is only half the length of the first when we put 220 volts in we will only get 110 volts out.

This is how a transformer works and we find transformers in televisions, flourescent lights, refrigerators, computers, in fact most electrical items we use. The power supply that we use for a laptop computer or a charger for a mobile phone is basically a transformer on a plastic box.

Voltage fluctuations can damage electronic equipment

Demand for electricity in Bali is greater than PLN (the nation's electricity supplier) can supply and as a result most of us have ongoing problems. A common problem (although many of us don't go around with a meter to check so we don't know) is that the voltage of our power supply fluctuates. It should be 220 volts but, when too many people are connected and drawing power, the voltage often drops to 180 volts (that's low) and sometimes I have known the voltage to drop as low as 150 volts (that's very low).

Anything that has an electrical motor such as a fridge, a water pump or an air conditioner needs a certain amount of power to run. If the voltage drops then the flow of electricity (the current - amps) has to increase to compensate. Now higher currents have a nasty way of harming things such as damaging sensitive equipment or electronic control circuits, wires might start to get hot. It is current that can give you an ongoing negative survival situation and it is also current that makes your circuit breakers cut out.

The voltage drops we from our power supplier can cause all sorts of problems so what can we do?

To stabilise the voltage we can install a voltage stabiliser.

A voltage stabiliser smoothes out fluctations

A voltage stabiliser, voltage regulator or stavolt, is a device that increases or decreases the voltage back to the steady 220 volts we want.

So how do we do that?

We have to do is make a transformer that continually adjusts itself. It looks at the voltage coming in and, using an adjustable transformer, it turns it into the correct 220 volts going out.

A voltage stabiliser has a large circular transformer with two coils, an input coil which is receiving power from our national grid and an output coil which is delivering power to our house. A contactor rotates from the centre of the transformer and slides along the coil so it can lengthen or shorten the coil and so adjust the voltage.

Voltage stabilisers we use in domestic or business electrical supplies are heavy devices. You will need one for each phase of power, if you have a single phase supply you only need one, if you have a 3 phase supply you will need 3 single phase stabilisers or a large 3 phase stabiliser. In Indonesia expect to pay around Rp6 million per phase excluding installation and any extra cabling.

Standard units have a minimum power capacity of 5 kilowatts and go up from there.

These units can increase or decrease voltage within reasonable limits typically handling anything from 160 volts to 240 volts and converting it back to 220 volts. They have protection switches so that if the incoming supply drops below 160 volts or above 240 volts they will switch themselves off.

Advantages of voltage stabilisers

Advantages are that they provide a constant, stable 220 volts protecting your valuable electrical equipment (and reducing blown lightbulbs). They remove those variations we all know about when the lights start to go dim or the telly goes on the blink. They also provide surge protection, absorbing sudden spikes in the power that can do damage.

Disadvantages of voltage stabilisers

Disadvantages are that they use a certain amount of power to operate so they will put the electricity bills up a bit and, if you are living close to your power limit, you may find an increase in the frequency your PLN circuit breaker (the big blue switch!) cuts out.

Another downside is that to boost a low voltage, they need to draw more current from the supply and this might also increase the likelihood of the main circuit breaker cutting out depending on how much power you are using and how much supply you have.

There are many different brands of voltage regulator which can get confusing at times. It is all to do with the quality of manufacture. My suggested brands are all Japanese which, in order of preference, are Kiumatsu, Yuritzu and Matsuyama. Matsuyama have a good backup maintenance service. I generally avoid cheap poor quality voltage stabilisers some of which may only last 6 months. Note that countries use Japanese sounding names so care is needed.

Finally you will find small voltage regulators for use with computers. Usually with small steel cases painted red or orange these are not in the same league as the serious units mentioned above and do not provide the same self adjusting voltage control. They make very good door stops and rather than buy one of these I would suggest you invest in a UPS (Uninterrupted Power Supply) for computers.

Copyright © Phil Wilson May 2011
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