L+△L (+1un)(2-△l)+l/] △L,△ 自感的相对变化L 1+(1),△ +61 1+=8 L +()1。1+(04 1+(l4) 同理,当总气隙长度增加△时,自感减小为△L2,即 Ll+△l+1 11-1+ 1+l4 1+(2°4)( ) ( )  r r l l l l l L L L =  +   −   +  +  1 ( )         +  −  +   =  r r l l l l l l l l L L         1 1 1 1 1 1 1 自感的相对变化 ( ) ( ) ( )         +         +    + +    + +    =   2 1 1 1 1 1 1 1 1 r r r l l l l l l l l l l l l L L             同理，当总气隙长度增加Δl δ时，自感减小为ΔL2，即 r l l l l L L     +  +  =  2 ( ) ( )         −         +    + +    − +   =  2 1 1 1 1 1 1 1 r r r l l l l l l l l l l l l            