[GreenKeys] Measuring Electromagnet Saturation?

[WA5CAB at cs.com]

That will work.  And is probably what an undergraduate would be made to do in 
a class on the subject.  But in practice (back when I was in practice), I 
would have either used a Gaussmeter and adjustable current supply to get an 
empirical answer or if I was sure that I knew what the core material and the number 
of turns in the coil was, measured its cross section, and used a B-H curve 
for the material to calculate the ampere-turns (NI) required to saturate it.

In a message dated 7/30/2007 6:06:00 PM Central Daylight Time, ham at cq.nu 
writes: 
> The setup is pretty simple.
> 
> Take two coils in series and run current through them. Ground one end  
> and bypass the end the power supply is connected to.
> 
> Then you measure the inductance and the "center point" with a fairly  
> normal inductance bridge.
> 
> The net result is that you can run the current up and watch the  
> inductance drop.
> 
> There also are ways to saturate the coil and then watch the spike as  
> you break the circuit. The pulse contains the energy stored in the  
> coil ...
> 
> Bob
> 
> 
> On Jul 30, 2007, at 12:02 PM, Brooke Clarke wrote:
> 
> >Hi Bob:
> >
> >I've been doing my homework on electromagnet saturation and found  
> >Electrical Silicon Steel as used in transformers, motors and newer  
> >electromagnets.  Not only higher saturation but also less remnant  
> >magnetization.  That's what's used as the core of the  
> >Synchronization coil in the WU 37SS clocks with the Sweep Second  
> >hand.  They were synchronized once a day using what looks like a  
> >Teletype loop running at 120 Volts and adjusted to 1/4 amp.  A one  
> >second pulse that ends at the top of the hour was used.
> >
> >In trying to come up with a circuit to drive the sync coil I'd like  
> >to have a way to know that the electromagnet is in saturation.
> >
> >Any thoughts on a test that would demonstrate saturation of the  
> >electromagnet?
> 

Robert & Susan Downs - Houston
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