Monday, June 21, 2010

Illumination in Stadiums - Introduction

A stadium comes to life when its fully packed to capacity and all its luminaries are working properly. Illumination in stadiums is a very important topic when it comes to the design phase of construction. The manner in which the luminaries are going to be installed impacts the overall performance of the stadium and not to forget the game being played. A well lit stadium/Arena ensures maximum illumination and minimal glare to the fans both on the pitch as well as on the seats. The lamps should be of correct rating to avoid unwanted glare and loss of heat through radiation. To achieve this, powerful luminaries are placed on top or even mounted on special masts at a height distance to reduce heat radiating to the fans and also making sure that maximum light falls on the pitch in the stadium. Less powerful  luminaries are then installed near the pitch to provide light for live television and quality photography.
All these lamps together with those inside the stadium present a power thirsty load to the power supply source. Today’s stadiums are supplied by up to 5 transformers and dedicated substations just to reduce power outages.

Wednesday, June 2, 2010

Which one is more dangerous, AC or DC?

This question has been asked by many people who have experienced an 
electric shock before.I recently received an electric shock from the 
domestic household current of 10A.The feeling was ecstatic. Many will come 
across large AC currents, but have you ever thought of DC Electrification? 
This would sound weird because DC current available in domestic premises 
is in the order of mA (milliamperes). In industrial environments  DC current 
is available in large quantities and is very lethal when handled improperly. 
The severity of a shock largely depends on:
---Amount of current 
---Amount of time on the exposure 
---Resistance of the body.
AC:Alternating Current
AC in theory would allow your muscles time to be able to move so that you could pull your hand / limb 
away from whatever it was that was giving you the shock. This is so because AC alternates from zero 
to maximum (amplitude) in a specified time frame (frequency).It is during this timeframe that muscle 
signals may retract you hand/limb...
The time frame we are talking about here is only a few milliseconds-which means that for larger 
currents, there is no time for reflex action. However as I said above,
 this largely depends on the amount of current flowing. 
Starting current of motors (128A) would never give you a chance of even thinking!
AC current will allow you to move your hand for the muscles which are not in the path of the electric
 current.In AC (Alternate Current) the muscles will contract and extend and through the spasms you 
might eventually free yourself (that is why people say that the current threw them while, in fact, 
it was their own muscles).