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Environmental Health Investigations Branch

General

Magnetic Fields (in mG) from Building Components
(Brief measurements of these fields were taken at one location and therefore do not account for all conditions that may exist.)

Distance From Source (feet)
source         1' 2' 5' 10' 25'
 
Transformer (Dry Type)  
from high-voltage side 33 16 5  -   - 
from low-voltage side 53 23 6  -   - 
from top going up 72 30 3  -   - 
 
400-amp Feeder  
part load-balanced 15 9 3 1  - 
(approx. 100 amps/phase with
full return current on neutral conductor)
     A phase = 100 amps     C phase = 115 amps
     B phase = 105 amps      neutral = 13 amps
full load-balanced 55 34 9 3  - 
(approx. 350 amps/phase with
full return current on neutral conductor)
     A phase = 360 amps     C phase = 320 amps
     B phase = 333 amps      neutral = 35 amps
full load-unbalanced 88 45 11 8 4
(approx. 350 amps/phase with
50% return current on neutral conductor)
     A phase = 360 amps     C phase = 320 amps
     B phase = 333 amps      neutral = 17 amps
 
Electrical Panel  
200A full load-balanced 373 148 27 7 1
600A full load-balanced 2052 881 173 45 7
1200A full load-balanced 6369 3478 579 142 22
 
Motor  
3-phase 8 HP 12 2  -   -   - 
1-phase 3 HP 15 3.5 0.5  -   - 
 

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1515 Clay Street, Suite 1700 Oakland, CA 94612