On Thu, 24 Oct 2002 18:00:26 +0200 "Peter L. Peres" writes: > On Wed, 23 Oct 2002, Ryan Haley wrote: > > *>Toroids have a higher inrush because they form a more efficient > magnetic > *>circuit. The hysteresis loop for a toroid is very square. I have > used some > *>120VAC/200A toroids and measured inrush currents of more than > 1600A. > > I believe what you say but it goes contrary to my experience. Good > toroidal transformers started within parameters will have less > inrush than > an EI job because they have a higher quality magnetic circuit and > they > more closely resemble a perfect coil than an EI cored one. However I > agree that starting a toroid with the load on the secondary (like an > unlimited rectifier followed by large decoupling caps) and no > current > limiting measures WILL cause more inrush. > I'm running WAY behind in my list email (couple big projects due REAL SOON NOW). Anyway, I believe toroidal transformers can have a large inrush current because of high magnetic retentivity of the core. If you turn the transformer off at a positive current peak, then turn it back on as the current heads positive, the core is already magnetized in that direction and soon saturates resulting in very high current. This is fixed in the next half cycle, but the first half cycle possibly has a very high current. Harold FCC Rules Online at http://hallikainen.com/FccRules Lighting control for theatre and television at http://www.dovesystems.com Reach broadcasters, engineers, manufacturers, compliance labs, and attorneys. Advertise at http://www.hallikainen.com/FccRules/ . ________________________________________________________________ Sign Up for Juno Platinum Internet Access Today Only $9.95 per month! Visit www.juno.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body