Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
ppt on ac vacuum circuit breaker
#1

ac vacuum circuit breaker

[attachment=45222]

introduction

the vacuum circuit breaker (vcb) is a single phase 25 kv circuit breaker used to protect power circuit for application on electric locomotives and electrical multiple units (emu
Reply
#2
Bhangar
Reply
#3
Vacuum Circuit Breaker



The Vacuum Circuit Breakers (VCB) are particularly advantageous for use in the voltage range 3 kV to 38 kV. In the Vacuum Circuit Breaker the arc interruption takes place in vacuum in the interrupter. The pressure inside the vacuum interrupter is maintained below 10-4 torr. At this low pressure very few molecules are available inside the interrupter chamber. This is one desired characteristic of the interrupting medium for more efficient arc quenching.

For opening the circuit breaker, the operating mechanism separates the moving contact from the fixed contact inside the interrupter. Just at the point of contact separation, a very small amount of metal vaporizes from contact tip and arc is drawn between the contacts. Current flows between the contacts through this arc. Due to the sinusoidal nature of the AC current, the current after reaching the maximum value decreases so reducing the vapour emission. Near zero value of the sinusoidal current wave the arc is extinguished. The metal vapour is deposited on the condensing shield  (see Fig-A). The space inside the interrupter being high vacuum, very little ions are available between the electrodes/contacts. So after arc extinction the space between the contacts regains dielectric strength very rapidly which is the most desired characteristics of the arc quenching medium. Due to the rapid regaining of dielectric strength of vacuum inside the interrupter the re-striking does not takes place. In the figure below is shown the main constructional features of a Vacuum Circuit Breaker (VCB).



The vacuum condensing shield is used so that the metallic vapour does not condenses on the enclosure glass. In the absence of the shield the metallic vapour condenses on the glass and gradually the glass becomes conducting, so that the insulation between the moving and fixed contacts is lost in the open condition of the breaker. The metallic bellow makes it possible to maintain vacuum inside the interrupter chamber while allowing the movement of moving contact for separation from the fixed contact. One side of the bellows is welded to the moving contact stem as shown while the other side is welded to the interrupter end plate. The contact surface is so designed that the arc between the contacts diffuse. The arc spread to the sides of the contact surfaces. Diffusion of arc reduces its strength hence the arc quenching is facilitated. The main requirements of the contact material is, very high electrical and thermal conductivity, low contact resistance and high melting point.

Advantages of VCB
  • The vacuum interrupters have long life. 
  • Unlike oil CB (OCB) or air blast CB (ABCB), the explosion of VCB is avoided. This enhances the safety of the operating personnel. 
  • No fire hazard.
  • The vacuum CB is fast in operation so ideal for fault clearing. VCB is suitable for repeated operation. 
  • Vacuum circuit breakers are almost maintenance free. 
  • Due to the rapid gain of dielectric strength of vacuum interrupter, the separation required between the moving contact from fixed contact is of the order of few millimetre. This makes the VCB compact.
  • VCB is light weight.
  • No exhaust of gas to the atmosphere.
  • Quiet operation.
Disadvantages of VCB
  • The main disadvantage of VCB is that it is uneconomical for use of VCB at voltages exceeding 38 kV. The cost of the breaker becomes prohibitive at higher voltages. This is due to the fact that at high voltages (above 38 kV) more than two numbers of interrupters are required to be connected in series.
  • Advance technology is used for production of vacuum interrupters. 
Reply
#4

Thanx
Reply

Important Note..!

If you are not satisfied with above reply ,..Please

ASK HERE

So that we will collect data for you and will made reply to the request....OR try below "QUICK REPLY" box to add a reply to this page
Popular Searches: vcb wikipidia, vacuum circuit breaker fractal pdf, future scope of vacuum circuit breaker, ppt topic of advance circuit breaker, siemens vacuum circuit breaker operation animation, vcb ac emu, free downloiad seminar topics of vacuum circuit breaker,

[-]
Quick Reply
Message
Type your reply to this message here.

Image Verification
Please enter the text contained within the image into the text box below it. This process is used to prevent automated spam bots.
Image Verification
(case insensitive)

Possibly Related Threads...
Thread Author Replies Views Last Post
  pistonless pump for rockets full report and ppt project topics 7 10,795 10-04-2016, 03:50 AM
Last Post: jaseela123
  landing gear arrangement : seminar report and ppt seminar post 2 689 05-03-2016, 07:34 AM
Last Post: dhanabhagya
  laser shot processing : seminar report and ppt seminar post 4 749 04-22-2016, 10:00 AM
Last Post: dhanabhagya
  a seminar on under water windmill ppt study tips 9 15,869 01-15-2016, 02:42 PM
Last Post: Guest
  ppt on hydraulic crane seminar projects maker 3 5,168 11-25-2015, 07:52 AM
Last Post: Guest
  engineering mechanics ppt study tips 1 2,482 11-17-2015, 06:00 PM
Last Post: Guest
  whitworth quick return motion mechanism ppt project girl 1 5,026 10-30-2015, 01:27 PM
Last Post: Guest
  vacuum braking system presentation Abstract 0 371 06-02-2015, 10:51 AM
Last Post: presentation Abstract
  vacuum brake system and modification presentation Abstract 0 274 05-09-2015, 06:55 AM
Last Post: presentation Abstract
  power generation from road speed breaker and from shoes presentation Abstract 0 274 05-09-2015, 06:51 AM
Last Post: presentation Abstract

Forum Jump:


Users browsing this thread: 1 Guest(s)