Test Corrections

Thread Starter

super70elco

Joined Oct 30, 2006
8
I took a test the other day and got a couple simple mistakes wrong but I cant seem to find the real answers on the web so I come here PLEADING to find some help....! I know these might be dumb questions but I cant find the answers to them any where.
1. What component is used for regulation in a power supply?
2. What does VCT mean in terms of power supplys?
3. When you have a cap tied to ground what is the purpose of that?

Please any help would be GREAT....! Thank you!
 

Papabravo

Joined Feb 24, 2006
13,560
1) The wiseacre answer is a voltage regulator. Another possible answer might be a zener diode.
2) VCT is an abbreviation for Volts Center Tapped. It refers to the configuration of a secondary output on a transformer. The center tap is a terminal on a transformer winding that is in the center of the winding. In a given application it may be used or unused.
3) A capacitor to ground provides a low impedance path for high frequency noise. It also removes ripple, or filters, the output from a halfwave, fullwave, or bridge rectifier.
 

JoeJester

Joined Apr 26, 2005
4,259
Forty years ago, one used a bleeder resistor to improve regulation, but somehow I don't think contemporary electronic designers would use such an inefficient method.
 

Papabravo

Joined Feb 24, 2006
13,560
Forty years ago, one used a bleeder resistor to improve regulation, but somehow I don't think contemporary electronic designers would use such an inefficient method.
And here I thought they were a safety feature to discharge large filter capacitors when the AC gets turned off. Nobody told me about improving regulation - frown!
 

JoeJester

Joined Apr 26, 2005
4,259
Yeah ... I always thought they were for safety too .... but that was one of those questions that typically caught people off guard. :)

Design an old type power supply ... FWR ... pi filter ... and then place a 100 ohm bleeder. Look at the regulation for a changing load, say 1k and above ...

I hated that question ... probably the primary reason it stuck with me after these many years ... :)
 
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