Electronic Schematics (alt.binaries.schematics.electronic) A place to show and share your electronics schematic drawings.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Posted to alt.binaries.schematics.electronic
external usenet poster
 
Posts: 98
Default Transformer inrush current--from RAT

Here are a couple of scope captures showing the inrush current at the primary of
a 500 VA toroidal power transformer. This transformer is in a bench power
supply rated at about 400 VA. The power supply main reservoir caps were
discharged before the captures.

The normal full load operating current is about 4 amps RMS.

In these images the grid voltage is green and the primary current is purple.

Tcur1 shows the current in the primary when the grid voltage is applied at the
peak of the sine wave. There's a small current surge of maybe 10 amps due to the
charging of the caps, but there is no large surge due to saturation of the
transformer.

Tcur2 shows the current in the primary when the grid voltage is applied at the
zero crossing (actually, just slightly before) of the sine wave. You can see the
nearly 180 amp surge which doesn't even begin until 5 mS after the voltage is
first applied. This surge current is so large that it distorts the voltage
applied to the primary by causing a substantial voltage drop in the building
wiring resistance. The DC resistance of the primary in this particular toroidal
transformer is about .5 ohms; that, plus the resistance of the building wiring,
etc., is what limits the current to 180 amps.




Attached Thumbnails
Transformer inrush current--from RAT-tcur1-png  Transformer inrush current--from RAT-tcur2-png  
Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Induction motor inrush current John Rumm UK diy 13 January 29th 08 07:59 PM
Simple hall effect current transformer..? Geir Holmavatn[_2_] Electronics Repair 5 November 11th 07 03:59 PM
different current transformer safe to use? Brotherwarren Electronics Repair 10 May 16th 06 03:59 AM
inrush current Wiebe Cazemier Electronics Repair 33 April 18th 06 01:41 PM
Low Voltage Outdoor Transformer Current Draw Tom in PA Home Repair 11 September 21st 05 08:53 PM


All times are GMT +1. The time now is 06:58 PM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"