TRANSFORMER can change electrical energy into voltage and current. Single phase transformer; consists of 2 windings of conductor wire in 1 core made of magnet or magnetizable material; the core usually consists of several layers AC current in the input winding (primary winding) provides energy.
Figure 6.116 Single Phase Transformer Circuit
Figure 6.117. Single Phase Transformer Without Load
The energy will flow through the magnetic core. The magnetic density will change according to the change in frequency and input voltage. On the output side (secondary winding) there will be an induced voltage that has the same frequency as the input voltage.
Transformer with open voltage
The transformer in the open state (without load) acts like a coil (inductor) with very large inductivity. In this condition, the transformer has no output current flowing to the load (because the load is open).
Open voltage; is the voltage on the output side when the transformer is unloaded. The induced voltage at the output can be calculated through the main equation of the transformer assuming that the open voltage is linear to the increase in the number of turns.
Voltage and current transfer in a transformer Assuming: there are no losses in the transformer (ideal transformer), then the voltage and current transfer can use the following equation:
[
Information:
V1 = Input voltage
V2 = Output voltage
N1 = Primary winding
N2 = Secondary winding
a = Transfer ratio
I1 = Current in the primary winding
I2 = Current in the secondary winding
Z1 = Impedance of the primary winding
Z2 = Impedance of the secondary winding
Summary
- Stabilized power supplies can use a regulator system or a switching system.
- There are many power supply specifications that we need to know in order to prepare for repairs.
- The distribution or wiring system of the power supply greatly determines the output results, so you have to be careful in implementing it.
- Even regulated power supplies must have safety features, so that the circuit being supplied is not damaged if damage occurs to the power supply.
- Regulated power supplies using an IC are simpler, so if there is damage it is easier to fix.
- Switched power supplies are usually used to supply large currents at low or medium voltages.
- An amplifier is a device with a small input signal that can be used to control a large output power.
- Amplifiers consist of several operating classes, namely: A, B, AB and C, each of which is used for its own purposes.
- Important amplifier specifications are: Gain, frequency response, input/output impedance, power output, efficiency and sensitivity.
- Types of distortion in amplifiers: amplitude distortion, frequency distortion, crossover distortion, phase distortion and intermodulation distortion.
- The noise that occurs in the amplifier is: thermal noise, shot noise and flicker noise.
- In a stereo amplifier, the left and right channel circuits are all the same, consisting of a preamplifier, a tone controller, and a power amplifier. Each has a different type of damage and a different handler.
- Telecommunication occurs because there is a receiver and transmitter, both on radio and TV.
- Color TV has two large blocks, namely the audio block (for sound) and the video block (for images).
- The video blocks on a TV are: tuner, IF, video detector, video amplifier, AGC, and vertical/horizontal deflection.
- TV repairs can be identified from the symptoms of damage that occur to the TV, and we determine which functions are not working.
Chapter 6 practice questions
- Name two types of power units and give examples of their use!
- Name two basic methods used to produce direct current (DC) voltage!
- Draw a block diagram of a series regulator and explain its working briefly!
- Mention the various types of safety devices in a series regulator power supply circuit.
- What are the advantages of using IC ?A 723 A as a regulated power supply?
- Mention the various types of switching power supplies!
- Draw a block diagram of a primary switched power supply and explain its working briefly!
- Name the classes of amplifiers and where to use them!
- What do you know about the efficiency and sensitivity of an amplifier?
- An amplifier has high frequency distortion that is amplified. What does that mean?
- Write down the parts of a stereo audio system and explain their functions!
- What is the use of the tuner and AGC circuits on a TV?
- In which block are the audio signals and video signals separated in a TV circuit?
Group task
By forming 4 children per group, open the back cover of a TV in your school's electronics lab (be careful not to input AC voltage to the TV, there is high voltage). Note / draw the outline of the PCB shape and write down the important component parts that are on the block diagram of a TV, for example: the horizontal part has a high voltage generator, namely a plyback transformer and so on. Discuss it with your instructor too!
A. Step Up Transformer
Is an electronic component that functions to increase electrical voltage. This component consists of 2 coils, namely primary and secondary made of nickelin wire (insulated wire). The secondary coil is usually more than the primary coil. But the primary coil is usually larger than the secondary coil.
Transformer (Trafo)
B. Step Down Transformer
It is an electronic component that functions to lower the electrical voltage. This component consists of 2 nickelin coils (primary and secondary). The primary coil is usually more and smaller than the secondary coil.
C. Adapter Transformer
It is an electronic component that is often used to make adapters, usually we can use an adapter transformer (Step Up or Step Down). The primary coil is connected to a voltage source (PLN), while the secondary coil will produce a DC voltage whose size depends on the number of coils or turns on the secondary.
D. Output Transformer (OT)
This component is also made of 2 coils, namely primary and secondary. OT transformers are usually used in the final radio receiver circuit. Its function is to adjust the impedance value required by the loudspeaker with the impedance value required by the transformer.
E. Input Transformer (IT)
The shape of the IT transformer is the same as the shape of the OT transformer. In the push pull amplifier circuit, IT is used for phase inversion, so that the two transistors in the final amplifier section work alternately, with the same phase state.
F. Spoel Oscillator and MF
Its physical form is small, consisting of primary and secondary coils equipped with a small ferrite rod that can be rotated. This ferrite rod is useful for trimming. Spoel Oscilator is used in transistor radio receiver circuits as part of a high frequency generator.
The MF transformer is similar in shape to the Spoel Oscillator. The difference lies in the number of turns and the color of the ferrite iron. MF is yellow, white & green, while the Spoel Oscillator is red. MF is also called IF, used in transistor radio receivers.
Common Damage to Transformers
- Break the primary coil.
- Break the secondary winding
- Connected (connected) between the primary and secondary parts.
- The primary or secondary part connects (connects) to the iron core.
- Material damage in the form of broken voltage branches/taps.
Uses of Transformers
- IT is useful for adjusting the input impedance and output impedance of the modulator circuit. It also functions to split the AC signal phase and output the information signal (voice).
- OT basically has the same function as IT, namely to match the input impedance with the output impedance in the modulator circuit.
- An adapter transformer is useful for lowering the electrical voltage from the mains voltage (PLN) to a voltage of 3 V, 12 V, 30 V or others without any wire connections.
How to Check a Transformer
- Before checking, first disconnect the transformer from the PLN source voltage.
- First check the primary coil (which is connected to the PLN source). If the needle moves to the right, it means the primary coil is still good.
- Check the secondary coil. If the needle moves to the right, it means it is still good.
- Check for short circuit between the primary and secondary. If the transformer is good, the needle will not move/deviate to the right.
- Check if there is a connection between the primary/secondary coil and the iron core. If the transformer is good, the needle will not move/deviate to the right.
- Transformers that have worn out/burned enamel wire insulation are not good to use. Even if checked there is no error. It is better to replace such transformers with good ones. This often happens to adapter transformers and output/OT transformers.