Synchronous motors are not self-starting. Some additional devices should be used to start the motor. Basically, there are two methods for starting synchronous motors: Induction motor starting (Damper winding) Auxiliary motor starting. Damper Winding Starting Most … [Read more...] about Starting Methods for Synchronous Motor
Electrical Machines
Need of a Starter (3 & 4 Point) in DC Motors
We use 3 and 4 point starters in DC motors. What happens if a DC motor is started without a starter? Let's check it. Consider a dc motor at standstill. When a dc motor is at rest the speed of the motor is zero, therefore the back emf is zero. We know that Back Emf, Eb= V - … [Read more...] about Need of a Starter (3 & 4 Point) in DC Motors
Current Transformer (CT) – Construction and Working Principle
A current transformer (CT) is a type of transformer that is used to measure AC current. It produces an alternating current (AC) in its secondary which is proportional to the AC current in its primary. Current transformers, along with voltage or potential transformers … [Read more...] about Current Transformer (CT) – Construction and Working Principle
Practical Transformer on No Load
Please read Ideal Transformer and Practical Transformer before continuing. Consider a practical transformer on no load i.e., secondary on open-circuit as shown in figure below. The primary will draw a small current I0 to supply (i) the iron losses and (ii) … [Read more...] about Practical Transformer on No Load
Why Current Transformer (CT) Seconday Should not be Open ?
Amazed why secondary of current transformer should not be open? If it is left open it may destroy the current transformer. So it is very important that the secondary of Current Transformer should not be kept open. The reason is quite interesting. Either it should be shorted or … [Read more...] about Why Current Transformer (CT) Seconday Should not be Open ?
Ideal Transformer and Practical Transformer
Ideal Transformer An ideal transformer is one that has no winding resistance no leakage flux i.e., the same flux links both the windings no iron losses (i.e., eddy current and hysteresis losses) in the core Although an ideal transformer cannot be … [Read more...] about Ideal Transformer and Practical Transformer
Properties of Good Transformer Oil
Even though the basic functions of the oil used in transformers are heat conduction and electrical insulation, there are many other properties which make a particular oil eminently suitable. Properties of good transformer oil are explained in this article. Organic oils of … [Read more...] about Properties of Good Transformer Oil
Percentage Impedance of Transformer and Its Calculation
What is the Percentage Impedance? The percentage impedance of a transformer is marked on most nameplates - but what is it and what does the Z% figure mean? The impedance of a transformer is the total opposition offered to alternating current. This may be calculated for each … [Read more...] about Percentage Impedance of Transformer and Its Calculation