Available online
Description
The aims of the programme are to show how the composition and structure of silicon-iron for a transformer core are chosen to minimise losses and then how the manufacturer achieves this desired comp...osition and structure.
The aims of the programme are to show how the composition and structure of silicon-iron for a transformer core are chosen to minimise losses and then how the manufacturer achieves this desired comp...osition and structure.
| Module code and title: | TS251, An introduction to materials |
|---|---|
| Item code: | TS251; 11 |
| First transmission date: | 23-06-1973 |
| Published: | 1973 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:21:32 |
| + Show more... | |
| Producer: | Tony Jolly |
| Contributor: | Ian Lowe |
| Publisher: | BBC Open University |
| Keyword(s): | Alloy composition; Core design; Domain walls; Kerr magneto-optic effect; Lamination; Rolling; Silicon-iron; Steelmaking; Temperature annealing |
| Footage description: | Shots of movement of the main wall of a large transformer, slowed down by a factor of 300. Ian Lowe indroduces the programme. Eddy current losses in electrical transformers are examined. Graph shows resistivity of several iron alloys. Increased resistivity of iron alloys decreases eddy current losses. Graph shows resistivity of iron/silicon alloy for various proportions of iron, silicon. Shot of phase diagram for iron/silicon alloys. Carbon content of the alloy is increased by 0.07% and this is shown on the graph. The graph illustrates the importance oif accurately controlling the carbon content if phase changes in cooling are to be avoided. Graph showing tensile strength/silicon content curve. At above 4% silicon content in the iron alloy, the tensile strength drops. Shots of steel being manufactured in an electric arc furnace. Scrap iron is the raw material. The sequence shows the steel being hot rolled into sheets and finally rolled up into large drums. Ian Lowe uses a perspex cube to aid his discussion on crystallographic direction. Graph shows magnetisation curves for a crystal of iron. Lowe explains why correct crystal orientation is important in transformer cores and why phase changes are to be avoided in the cooling process during the manufacture of laminates. Lowe examines magneto-static force. He uses a pair of magnets and a steel bearing suspended on a string. Lowe shows how domains move with the application of magneto-motive force in a single crystal of iron. He explains the experimental apparatus and then carries out the experiment. As electro-motive force is increased the domain wall moves. Lowe explains how large grain, correctly oriented transfoimer steel is made. He uses a model of a steel making plant to aid. Manufacturing, of transformer cores is examined. Shots of sheet steel being manufactured into transformer core laminates and laminates being assembled to form cores. Lowe discusses the effect of stresses on domain. Lowe sums up. |
| Master spool number: | 6HT/70953 |
| Production number: | 00525_5037 |
| Videofinder number: | 1563 |
| Available to public: | no |
