Transformer soft-start with relays - Page 4 - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 14th October 2010, 10:34 AM   #31
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally Posted by metalsculptor View Post
It works fine I posted examples in a prior thread, I had the problem that Andrew T mentioned once because the series resistor was too high, aim for 5x the full load current at start for a soft start.
I want to use a close rated fuse in the primary feed. I find I can get away with a fuse ~=maximum rated current if the soft start resistor limits the peak current to ~3X maximum rated current.

The lower the required fuse rating the worse the risk of the relay not pulling in.
This problem goes away if a real timer circuit is adopted.

Metal,
you are right the Zener makes the non activation of the relay much worse in low voltage conditions.
__________________
regards Andrew T.
  Reply With Quote
Old 14th October 2010, 11:44 AM   #32
diyAudio Member
 
Join Date: Sep 2010
Location: Melbourne
Quote:
Originally Posted by AndrewT View Post
I want to use a close rated fuse in the primary feed. I find I can get away with a fuse ~=maximum rated current if the soft start resistor limits the peak current to ~3X maximum rated current.
I tend to use circuit breakers, which have no problem starting a 5x rated load but trip a bit slower than a fuse, the reasoning being that it is difficult to protect semiconductors with a fuse, so protecting the rest of the system is the primary goal and a bit of surge rating is quite handy for testing, 2x overload for a few minutes doesn't bother a robust power supply. The majority of industrial control power supplies in Australia are protected by cheap DIN rail mounted MCB's which for around A$6 are quite competitive with fuses. The physical size of an MCB compared to a 3AG fuse can be problem for a small PSU.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Soft Start again marsheng Power Supplies 0 29th June 2010 10:09 AM
Need a soft start? maxpou Solid State 19 18th April 2007 09:23 PM
Soft-start circuit with no relays and no aux. transformers Eva Power Supplies 72 23rd March 2007 08:30 AM
Soft start & Soft Switch circuit: can anybody help? m.parigi Solid State 95 22nd August 2005 03:32 PM


New To Site? Need Help?

All times are GMT. The time now is 01:23 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2