Satyadev Vyas's Blog (42)

Why can a 50Hz CT work on 60Hz systems, and why can't a 60Hz C.T. work on a 50 Hz system?

CT or PT functions on the principle of electromagnetic induction. The electrical energy is first converted into magnetic energy and again the magnetic energy is converted in the electrical energy. The electrical current first converted in magnetic energy. The magnetic energy is nothing but converting electrical current into flux. The flux then flow through the core. The core of the CT or PT has its maximum flux carring capacity.…

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Added by Satyadev Vyas on August 12, 2020 at 10:56pm — No Comments

What is Battery Acid?

In general battery acid refers to the electrolyte in a lead acid battery. That is a diluted form of sulfuric acid (H2SO4) in water generally in the concentration of 36–40%. As such it does not have the burning properties of concentrated sulfuric acid.

Battery acid is rather unique in battery electrochemical systems because it not only carries ionic…

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Added by Satyadev Vyas on August 12, 2020 at 9:57pm — No Comments

What is insulation class of transformer oil?

The insulation class of the transformer refers to the max (hot spot) temperature that can be safely withstood by the specific insulation material. It is the weakest of the materials used in transformer (as far as temperature withstand capability is concerned) as the other materials like steel core & copper winding can withstand much higher temperature during operation. There are different classes of insulation materials (Y, A, B, F, H & C) with max temperatures 90, 105, 130,…

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Added by Satyadev Vyas on August 7, 2020 at 11:31pm — No Comments

The terminal voltage is less than the EMF of a cell or a train of cells. The cell voltage is the voltage available at the terminals of the battery. This is equal to EMF - Voltage drop(s)due to intern…

  • The terminal voltage is less than the EMF of a cell or a train of cells. The cell voltage is the voltage available at the terminals of the battery. This is equal to …
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Added by Satyadev Vyas on August 7, 2020 at 11:23pm — No Comments

Why battery terminal voltage is less during discharging of battery?

  • The terminal voltage is less than the EMF of a cell or a train of cells. The cell voltage is the voltage available at the terminals of the battery. This is equal to …
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Added by Satyadev Vyas on August 7, 2020 at 11:00pm — No Comments

What is the relatioship between power factor and air gap of an induction motor?

Airgap of the induction motor is inversely proportional to the power factor and efficiency. The Airgap between stator and rotor decides amount of energy transferred from stator to rotor. Airgap incteases the loss of fluxes transferred from stator to rotor. Thus efficiency decreases if Airgap increases ,

now comming to the part of power factor :-…

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Added by Satyadev Vyas on July 31, 2020 at 12:05am — No Comments

What is the relatioship between power factor and air gap of an induction motor?

Airgap of the induction motor is inversely proportional to the power factor and efficiency. The Airgap between stator and rotor decides amount of energy transferred from stator to rotor. Airgap incteases the loss of fluxes transferred from stator to rotor. Thus efficiency decreases if Airgap increases ,

now comming to the part of power factor :-…

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Added by Satyadev Vyas on July 31, 2020 at 12:05am — No Comments

What happens if air gap of induction motor increase?

If the air gap of an induction motor is increased, the following will happen:

  • The permeability of the magnetic circuit rotor-to-stator will decrease.
  • The magnetizing inductance of he motor thus decreases.
  • The…
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Added by Satyadev Vyas on July 31, 2020 at 12:01am — No Comments

What is the effect of the air-gap length on the efficiency of an induction motor?

The reluctance of the magnetic circuit increases with an increase in the air gap length. To produce the same flux in the motor, the stator winding draws more current if the air gap length is increased. with an increase in air gap length, the fixed losses in the motor increase and the motor efficiency deteriorate.

Flux= MMF/Reluctance of the magnetic circuit…

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Added by Satyadev Vyas on July 30, 2020 at 11:58pm — No Comments

What is dispersion coefficient of induction motor?

The dispersion coefficient is defined as the ratio of magnetizing current to ideal short circuit current. 34. What is the condition for obtaining the maximum torque in case of 3 phase induction motor? The maximum torque occurs in induction motor when rotor reactance is equal to rotor resistance.



Read More:… Continue

Added by Satyadev Vyas on June 15, 2020 at 5:30am — No Comments

What is dispersion coefficient of induction motor?

The dispersion coefficient is defined as the ratio of magnetizing current to ideal short circuit current. 34. What is the condition for obtaining the maximum torque in case of 3 phase induction motor? The maximum torque occurs in induction motor when rotor reactance is equal to rotor resistance.



Read More:… Continue

Added by Satyadev Vyas on June 15, 2020 at 5:30am — No Comments

What are Triplen Harmonics?

Lower order harmonics are of more concern than higher order harmonics. Harmonics by default refers to current harmonics. The impedance of the device or circuit is mostly inductive and so is equal to R+jwL, where w=2*pi*f. Hence it can be observed from the equation that the impedance offered is directly proportional to frequency. The frequency of the 3rd order is 3w, 5th order is 5w ... Hence as the order of the harmonics increases, the impedance offered to them increases and so they are less in… Continue

Added by Satyadev Vyas on June 15, 2020 at 5:27am — No Comments

CT Knee Point Voltage Calculation Method

Test Procedure for knee point Voltage calculation of CT :



1.Disconnect the CT from all external connection

2.Note down the knee point voltage of CT ( as per datasheet of the CT).

3. Apply 5-10 % voltage of the knee point voltage to the secondary of the

CT by auto-transformer. Note down the secondary current.

4.Increase the voltage gradually to 20,30,40,50,60,70,80,90 % of the

rated knee point of the CT and note down the secondary current.

5. Now increase… Continue

Added by Satyadev Vyas on June 12, 2020 at 3:49am — No Comments

Effect of Over fluxing in Transformer

Some of the effects of over fluxing are as follows:



i. Significant increase in core losses.



ii. Formation of hot spots.



iii. Increased leakage flux and magnetizing current.



iv. Delayed operation in case of inverse-time over current relay.



v. Over-reach and under-reach problems in impedance relays.



vi. Introduction of harmonics.



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Added by Satyadev Vyas on June 12, 2020 at 3:41am — No Comments

Over fluxing in Transformer

ransformers are among the most important and expensive equipments that always been used in industry and power system. Transformers are generally designed to work just below peak value of magnetic flux, so proper analysis of transformer behaviour under over fluxing condition is necessary.



Transformers are designed in such a way that under steady state operating conditions they can operate near peak magnetizing flux but below the saturation level. When the transformer core is… Continue

Added by Satyadev Vyas on June 12, 2020 at 3:39am — No Comments

What are Triplen Harmonics?

Triplen Harmonics – The triplen harmonics are defined as the odd multiples of the 3rd harmonic (ex. 3rd, 9th, 15th, 21st etc.). Triplen harmonics are of particular concern because they are zero sequence harmonics, unlike the fundamental, which is positive sequence. The consequence of this fact is that the magnitude of these currents on the 3 phases are additive in the neutral. This can lead to very large currents circulating in the neutral, and unless the neutral is sufficiently oversized this… Continue

Added by Satyadev Vyas on June 12, 2020 at 3:36am — No Comments

Difference between harmonics and sub-harmonics

For 50 Hz power signal, its integer multiple frequencies of 100, 150, 200, 250 Hz are called harmonics.



In some cases signal waveform is distorted and creates sub harmonics which are waves of lower frequencies such as 25 Hz , 12.5 Hz or lower.



Higher harmonics are bad for magnetic equipment because the iron losses are proportional to square of frequency so higher frequency means more heating of magnetic core.



I am not aware how sub-harmonics can distort the… Continue

Added by Satyadev Vyas on June 12, 2020 at 3:35am — No Comments

Effect of Harmonics on Capacitor Bank

Harmonics are two types space harmonics and load harmonics .



Even harmonics appear at the load side at odd harmonics back the supply side . The even harmonICS are less significant they are like 2f , 4f , 6f etc and odd harmoNICS matters the stability of the system they are 3f , 5f , 7f , 9f , 11f etc.



Harmonics are much significant for star connected three phase winding and for delta connected winding the harmonics are minimum .



Space harmonics takes due to… Continue

Added by Satyadev Vyas on June 12, 2020 at 3:31am — No Comments

Why induction motor is called asynchronous motor?

The induction motor function if there exist slip between the synchronous speed and the actual speed of the rotor. The rotating magnetic field rotates at the synchronous speed in the air gap, however the flux that links to the rotor conductor has less speed than synchronous speed, The difference between the speed is called slip.The slip cause current to flow in the rotor conductor and as a result…

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Added by Satyadev Vyas on April 24, 2020 at 10:07pm — No Comments

Why CT secondary should not be left open?

During normal operation of CT, the primary and secondary winding produces mmf which by lenze’s law opposes each other. As the secondary mmf is slightly less than the primary mmf, the net mmf is small. This net mmf is the working/magnetizing mmf of the core of CT.

Now, in case secondary winding is kept open, then secondary current will be zero while the…

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Added by Satyadev Vyas on April 20, 2020 at 4:52am — No Comments

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