Tony,
Yes and looks good. I'll sure check them out, do you have the Direcnic URL?
Thanks also for the comment about the transformer article. I saved it into a
PDF, re did it correctly, plus a spell check if anyone would want it. If so,
just e-mail me and I'll send it.
Best,
Will
*********** REPLY SEPARATOR ***********
On 4/17/05 at 10:40 PM Tony King wrote:
>Will,
>
>Great explanation of the transformers. Thanks!
>
>BTW... did you get my email re web pages?
>
>73, Tony W4ZT
>
>
>Will Matney wrote:
>> I actually screwed up a bit not watching myself and typing too darn fast.
>>
>> Silicon is added not just to help with eddy currents but to keep the
>core from staying magnetized or relieving "residual magnetism"! Sorry
>about that faux pas, I was in too big of a hurry and forgot to include it
>which is really important. I do that sometimes so please excuse.
>>
>> Best,
>>
>> Will
>>
>> *********** REPLY SEPARATOR ***********
>>
>> On 4/17/05 at 10:02 PM Will Matney wrote:
>>
>>
>>>Hipersil, the myth and the truth.
>>>
>>>I was asked about a transformer off this mailer using nothing but a
>>>Hipersil transformer. I offered an EI type, M6 material transformer of
>the
>>>same specs, but it wouldn't do. Well folks, this gave way to me writing
>>>this for all on what exactly is a Hipersil transformer.
>>>
>>>Hipersil is a trademark owned by Westinghouse Electric for a type of
>>>transformer core and material they manufactured at one time. Hipersil,
>the
>>>material, is mearly a cold rolled, grain oriented, silicon steel with
>>>about 3.5% silicon added. That's it, nothing more. M6 material is the
>same
>>>material offered by several steel manufacturers, and is what Westinghouse
>>>bought in large coils. M6 is the AISI number for 3.5% silicon steel which
>>>has been cold rolled, with the grain oriented in the rolling direction.
>>>
>>>
>>>What is cold rolled, grain oriented (CRGO)?
>>>
>>>This is a type of steel, which after being rolled out to a strip, or
>>>sheet, is cold rolled again to where the grain of the steel orients
>itself
>>>in a certain direction. What this does is drop the reluctance of in steel
>>>to the magnetic flux, which in turn lowers its losses, nothing more.
>>>
>>>
>>>Why add silicon?
>>>
>>>Silicon is added to control eddy currents in the core and thus lower the
>>>losses. The thinness of the laminations controls this also. There is
>>>different grades of silicon steel, with varying amounts of silicon. On
>the
>>>lower end is non oriented silicon steel (CRNO) which wasn't cold rolled
>>>for the grain to line up like M50. On the upper end is M6 which is about
>>>the top of the heap for CRGO steel without other alloying agents being
>>>added such as cobalt ot nickel.
>>>
>>>
>>>What is a Hipersil core?
>>>
>>>Well, there is many "Hipersil" cores if you want to call them that,
>>>including EI cores, but the steel manufacturers just use the M numbers to
>>>designate the steel. The proper question is what is a "cut core" or a
>>>"C-Core"? A C-core is made by winding a thin strip of CRGO or CRNO steel
>>>around a rectangular or square mandrel in a lathe. The steel strip has an
>>>adhesive on it so it will bond together after it is rolled to a certain
>>>thickness. This strip can be several thicknesses where 14 mils is a very
>>>common one. The very thin ones like 2 mils is for higher frequency work
>in
>>>the audio frequency range. 14 mils is commonly used in power transformers
>>>for 50 and 60 Hz.
>>>
>>>After the core has been wound to the proper thickness, it is generally
>>>annealed to improve its properties, or some are pre-annealed. It is then
>>>bonded so it cant come apart. Next, the core is transfered to a band saw
>>>and cut in half. Each half is marked and then the cut faces are either
>>>machined or ground for a close fit when put back together. this helps
>>>eliminate the air gap if any.
>>>
>>>
>>>Why is a Hipersil core touted to be better than an EI core?
>>>
>>>Well, there's a lot of myth and mis-information here. The only difference
>>>between a cut core and an EI core using the same material is weight. This
>>>weight savings is due simply to the corners being rounded off where an EI
>>>core is rectanglar overall, that's it, nothing more. The weight savings
>>>you'll get is from 15% to 20% just because the corners are rounded off.
>No
>>>matter what, each type core has to have the same core area (A) in each
>>>type.
>>>
>>>A cores power handling ability (in watts or volt amperes) comes from its
>>>ability to cram all the magnetic lines of force (flux) into a small area
>>>(flux density). Every core has a maximum flux density (Bmax) which is
>>>determined by the cross sectional area of the core (A) and the material
>>>the core is made from, nothing more. If this limit is exceeded, the core
>>>goes into saturation. This means that any more increase in current does
>>>not cause any more flux in the core. It also means the the cores
>>>permeability drops off sharply at this point. A core is designed to not
>>>saturate when maximum power is drawn from the transformer (this is not
>the
>>>case in an inverter). Generally, a flux density is selected which is just
>>>below Bmax at design time. Lets say the material gives a Bmax of 14,500
>>>gauss. A working flux density of maybe 14,000, or 13,500 might be used.
>>>However, this increases the weight of the core because more iron has to
>be
>>>added to it to keep the flux density down. This is w
>>>hy when selecting a transformer, you should figure the maximum current in
>>>amperes to be drawn for each winding including losses. Losses in most
>>>filtered power supplies run around 5% or so. The reason for this is the
>>>designer trys to make the transformer as light as possible and this in
>>>turn means they design the transformer to run as close to saturation as
>>>possible without going over. On designing power chokes, the DC portion
>has
>>>to be considered along with the AC to keep away from saturation. The core
>>>can be gapped to correct some of this, but that is more than what can be
>>>covered here at this time.
>>>
>>>
>>>What are the disadvantages to a C-Core?
>>>
>>>First and foremost is cost. The cost of pre-made cores is expensive
>unless
>>>buying a large quantuty of each size. The mounting hardware costs more
>>>than does on an EI core of the same size. The last, and an important one
>>>is that a C-core runs hotter than an EI core of the same size. This is
>due
>>>to the mass of iron being smaller than on an EI core, plus the fit of the
>>>bobbin to the core. The only plus to a C-core is labor savings, and a
>>>minor weight savings. It doesn't take as long to put together a C-core as
>>>it does to stack an EI core. However, an experienced builder can go
>pretty
>>>darn fast stacking the lams of an EI core, even being interleaved.
>>>Actually, a tigther fit can be achieved of the coil to the core on an EI
>>>core than a C-core because of adding the lams, one at a time to the exact
>>>thickness needed. With a C-core, you get the one thickness, that's it. To
>>>make it fit, extra paper or wedges is used a lot. This also makes one
>heat
>>>up more if the bobbin doesn't have a tig
>>>ht fit to the core. This raises the cost of the mandrel used to wind the
>>>coil as it's tolerances are greater.
>>>
>>>
>>>Is an EI core better than a C-core?
>>>
>>>In my opinion, Yes! The reason being is the heat. Heat is the killer of
>>>all electrical and electronic components. I wouldn't care if the core
>>>weighed 20% more as long as it lasted longer.
>>>
>>>
>>>The above is just my opinion on the subject, and hope more have been
>>>brought into the light on the differences between these two types of
>>>transformers.
>>>
>>>Best,
>>>
>>>Will
>>>
>>>_______________________________________________
>>>Amps mailing list
>>>Amps@contesting.com
>>>http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>>
>>
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