Transformer: Necessity in Robotics

This article is all about transformers. A transformer is an electrical device used to transfer electrical energy from one winding to another. For this it uses the phenomenon of magnetic induction. There are two windings; primary and secondary. The current flowing in the primary winding varies, which helps in producing a varying magnetic flux. The varying magnetic flux flows into the secondary windings as well and causes production of an EMF or voltage in the secondary winding.

Electromagnetic induction is the phenomenon in which an electrical current is produced across a conductor with the help of a magnetic field.

It is stated that electromotive force which is produced around a closed path is directly proportional to the rate of change of the magnetic flux through any surface which is bound by that path. This is applicable when a conductor is moved inside it or its strength is changed by any means. A transformer uses the concept of Faraday's law. The core which we used inside the coil must be of iron so that we can use its ferromagnetic properties and electromagnetic induction phenomena can be used. The transformers are of two types: step up and step down transformer. It all depends on the number of primary and secondary windings that the transformer is stepped up or stepped down. If Ns, number of turns in secondary coil is more than the turns in primary coil, Np then it is said to be as step-up transformer.

Basic Principle on which it works: The transformer actually works on two principles. First that an electric current can produce magnetic field and second principle is that a varying magnetic flux can induce voltage in another coil. When the secondary coil is open circuit the primary coil acts as a pure indicator.

What happens actuallyis that the current which passes through the primary coil creates a magnetic field. Inside these primary and secondary coils, a core of high permeability is used. Most commonly we use Iron as a core. Transformers are bi-directional, and will work regardless of where the input is connected.

Now we know that when the secondary coil is open circuit then the primary coil acts as a pure inductor. When a load is connected to its secondary coil then a current will start flowing in its secondary windings. While using the transformer some rules should always be kept in our mind: Voltage in very excess should not be applied on the windings, a specific Direct current should not be allowed to flow through any winding and the last but not the least and frequency should not be less than the applied frequency.

However, you can always apply less than the rated voltage to any winding, and use any winding as primary or secondary, so long as the current rating is not exceeded. Any frequency higher than the rated frequency is also safe.

Ideal transformer is that transformer in which no losses has occurred and it gives output at 100% efficiency but because it is not possible practically and hence there are always some losses occurred during its working due to power dissipation and hence we will now discuss about some of the important losses which can occur during its operation. These losses are caused due to so many reasons such as material used, number of windings and size also contributes in causing losses. The transformer has windings and these windings have resistance, the resistance causes losses in the form of heat. These losses are divided into mainly two parts : Copper losses and Iron Losses.

Transformer losses are divided into losses in the windings, termed copper loss, and those in the magnetic circuit, termed iron loss. Losses in the transformer arise from: Winding resistance

Winding resistance: the resistance inside the wiring causes losses of power in the form of heat some of its energy gets dissipated. Another type of loss that can exist is that when the magnetic field is reversed, a small amount of energy is lost in the cycle. This loss occurs inside the core. Here is another type of loss as well which is caused due to eddy currents. Eddy currents circulate within the core in a plane normal to the flux. Eddy current losses can be reduced by making the core of a stack of plates electrically insulated from each other. It occurs for transformers as all transformers operating at low frequencies use laminated or similar cores. Except all these, leakage currents are also a big reason for the losses.


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