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Line voltage not only varies with load, but also with reactive power. The power company will seek to reduce reactive power on their lines because it's all loss to them which cannot be billed to most customers. And based on % load, those power transformers which are not 100% loaded, also generate reactive losses [measured as volt-amp, reactive, or VARs (or Kilo-VARs)]. This is where POWER FACTOR comes in. Electrical equipment will have a power factor rating of less than one, but the higher the number, the better it is.
A modern substation uses electronic tap-changers to compensate for voltage changes when the load changes. They keep the voltage stable, but only at the substation. If you are some distance from the substation, voltage can vary considerably. Most reactive power is caused by transformers & AC motors. To help reduce this fluctuation, the power company adds capacitors across the line. The capacitor will also create a reactive current, but it flows in the opposite direction as inductive-VARs. If properly inserted, the two reactive currents will cancel each out & the net result will be less loss in the power system and more stable voltage for the customer. Follow your power line back toward the substation. You will likely find three capacitors & a small transformer mounted on one of the power poles. If the fuses are blown the capacitors won't work. The power company is not likely to discover failed capacitors unless someone complains of low voltage. John S. -----Original Message----- From: markc@kjly.com To: crtech@crtech.org Sent: Fri, 1 Dec 2006 12:02 PM Subject: [CRTech] Voltage swings was Re: [CRTech] New 5 KW AM Transmitter
----- Original Message -----
From: "Scott Todd" <stodd@kkms.com>
To: "CRTech" <crtech@crtech.org> Sent: Friday, December 01, 2006 10:56 AM Subject: Re: [CRTech] New 5 KW AM Transmitter > Sometimes it would be down around 114 and it sometimes jumped to 126. If > the voltage rose while the lower voltage one was on the air, come pattern > change it wouldn't come back on. If I heard little hiccups in the audio > on the one set to high, I knew voltage dropped again and it was time to > switch to the other one. > > > Scott Todd Sure was an eye-opener for me when I learned what was an acceptable range to the electric company. No wonder the motorized APC in the transmitter wears down the rheostat at some sites. Mark MN --------------------------------------------------------------------- For CRTech resources visit http://CRTech.org/ To unsubscribe, e-mail: crtech-unsubscribe@crtech.org List problems? E-mail: TechStaff@CRTech.org | ||||||||||
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