Читайте также:
|
5.1 To learn|studies,learns| and note| the method of calculations|computations| of efficiency of protective screens from ЕМF| | and radiation.
Knowing descriptions of metal, it is possible to expect|calculates| the thickness of screen!!! 6. mm|, providing|securing| the set weakening of the electromagnetic fields on this distance:
(6.1)
where 
- is angular frequency of alternating current, rad/s; 
- is magnetic permeability of metal protective screen, G/m; 
- is electric conductivity of metal of screen, 
; 
- is screening efficiency on a workplace|job|, that concernes by expression
, (6.2)
where Нх| and Нхе -| are maximal values|importances,meaning| of tension of magnetic constituent of the field in the distance х, m, from a source|spring| accordingly without a screen and with a screen, А/m. Tension of Нх|, can be certain|definite| from expression
, (6.3)
where w and a is number of coils|turns| and radius of spool|bobbin|, m; I - is strength of current in a spool|bobbin|, A|but|; x -distance from a source|spring| (spools|bobbins|) to|by| the workplace|job|, m; 
- is a coefficient|ratio|, that concernes by correlation of x/a (at x/a>10 =1), If the possible electric constituent of the field is regulated Ep, a magnetic constituent can, to be certain|definite| from expression
(6.4)
where f - is a field frequency, Hz.
5.2. To expect|calculates| efficiency of metallic protective screen for the decline|lowering| on the workplace|job| of ЕМF| | radiostrengthener|amplifier| the initial|output| contour of which|what| has the spool|bobbin| of variable|changeable,changing,exchange,removable| inductance: the radius of spool|bobbin| is evened and|but|, number of coils|turns| \ in, strength of current|corn-floor| in a spool|bobbin| and his|its| frequency is evened And and f accordingly. Distance from a spool|bobbin| to|by| the workplace equels|job| х.
Table 6.1 Variants of basic|outputs| data|information| for a task.
| Parameters | First figure of variant | |||||||||
f,  Hz
| 6,5 | 7,5 | 8,5 | 9,5 | ||||||
| I, A |
| Parameters | Second figure of variant | |||||||||
| W | ||||||||||
| x, m | 0,7 | 0,75 | 0,8 | 0,85 | 0,9 | 0,95 | 0,7 | 0,8 | 0,6 | 0,9 |
Example. To expect|calculates| efficiency of aluminium screen by the radius of R=0,35 m, when it is known:
f = Hz; = 4 
G/m; ’ = 1; I=380 A; W=14; a= 0,1 m; x=0,8 m.
Decision. 1. We determine possible enormous magnetic constituent of the field of ñ
by an account, that possible tension of the field of Еa.t.=| 5 V/m (on sanitary
to the norms|standards|):
A/m 5
2. Tension on a workplace|job| without a screen
A/m
3. Necessary efficiency of screening on a working city|town|.
4. Actual|real| efficiency of screening on a workplace|job|.
where d|but| is thickness of screen, mm|: 
- is depth of penetration of the field in a screen, m; ( ’) -relative magnetic permeability of screen ( ’ ' = 
).
From the structural looks we adopt a si = 1ìì.
Thus|on this grow|, Ехa| =10,5 >Ехnes =1,57, that screen is select provides|secures| necessary defence|protection| on this workplace|job|.
Дата добавления: 2015-11-14; просмотров: 64 | Нарушение авторских прав
| <== предыдущая страница | | | следующая страница ==> |
| Laser radiation | | | Practical work 1: Matrixes. Operations over matrixes. |