DC Series Motor Advantages & Disadvantages

In DC series motor field coils or winding will be in series with the armature winding. The conductor size of the field winding will be having a thick wire (large cross section) with lesser turns. Advantages of DC Series Motors The main application where series motors are best suited is for traction applications. The torque … Read more

DC Motor Applications in Industries

In spite of the wide use of AC supply, DC machines have some advantages compared to ac motors and are used in industries for some applications. Some of the DC Motor Applications in Industries are listed below. Applications of DC Series Motor DC series motors are widely used for electrical traction applications, i.e, these motors … Read more

Eddy Current

We have seen that whenever the flux, linking with a closed electric circuit changes, an EMF has induced in the circuit and a current flow, the value of which depends on the emf around the circuit and the resistance of the circuit. It is not necessary that the circuit be a wire and that the … Read more

Why is transformer rated in kVA and not in kW?

The power rating of a transformer or any electric machines indicates the maximum value of voltage and current it can carry without over-heating. Power = Voltage(V) × Current(A) × Power factor As transformer is considered as a power source while the induction motor is considered as a load. Manufacturers of Transformers cannot predict the power … Read more

Losses in a DC Machines

Q. What is meant by “energy loss” in a machine? Answer. Whole of the input energy to the electrical machine is not converted into useful output energy but a part of the energy is converted into heat and is lost for the useful purpose of the machine. The energy converted into heat is called the … Read more

Electric Braking

Q. What are the requirements of good electric braking? Answer. The requirements of good electric braking are: (i) The braking should be quick and reliable in action. (ii) The braking must be controllable. (iii) Some suitable means must be provided for dissipation of kinetic energy of the moving parts of the motor and its driven … Read more

Parallel Operation of DC Generators

For supplying a large DC load, it is desirable to use more than one generator in parallel. This arrangement provides the security that if one generator gives way, the other(s) can feed part load. Desirable Conditions for DC Generators in Parallel Same voltage rating Same percentage voltage regulation Same percentage speed regulation of the prime … Read more

Electrical Machine Insulation

In electrical machines, the insulation system must withstand the high electrical stresses and severe mechanical stresses induced by the magnetic field of the moving rotor. In machines, multi-turn windings are put in narrow armature slots, which are usually grounded. Rotating machine stator insulation construction is divided into principal types: Random wound conductor machines with small … Read more

Insulating Materials for Power & Distribution Transformers

The insulating materials used in power and distribution transformers must possess the following properties: Good electrical properties to withstand the power frequency (50 Hz) voltages and impulse overvoltages. Good mechanical properties to withstand fabrication and handling during manufacture and electromagnetic forces during overload, short circuit, and normal operating conditions. Good thermal stability and low ageing … Read more