Re: Mains Current Monitoring
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Friday, March 19, 1999 10:23 AM
Subject: Mains Current Monitoring
>Original Poster: "Basura, Brian" <brian.basura-at-unistudios-dot-com>
>I'm in the process of building a new power controller for my coils. The
>question I have is on measuring input (mains) current which can be up to 50
>amps. I'd prefer to do it without utilizing a shunt. Can I build a
>transformer by taking a toroid core, wrapping one turn of a primary leg
>around it, then winding 100 turns around it for a secondary, and hooking
>secondary to a .5amp meter?
That is exactly what a current transformer is.... You'll need to select an
appropriate toroid core material (i.e. ferrite won't do). The ideal would be
a core from a toroidal power transformer. And, the one turn primary is just
passing the wire through the middle of the core once.
Take a look around at surplus places, current transformers are quite common.
The standard is to put a 0-5 A meter on the secondary, so they are rated
like 200/5 meaning 200A through the center makes 5 A through the secondary.
The secondary must be loaded with a low impedance load (like an ammeter) or
the core saturates and you make HV spikes.
Surplus current transformers run about $5-10
The other option is to get some of the solid state current sensors based on
Hall Effect. They run about $20-30 each. Check the Newark catalog.