PURPOSE: To facilitate the insertion or removal of pressure-sensitive paper with the improvement of working efficiency of winding work, by providing a spacer with a structure of two or more pieces common with each winding with the spacer constituted of adiabatic material.

CONSTITUTION: The through spacer 10 constituted of heat insulative material is placed common over each winding on the upper ends of the windings 2aW2c further divided into two in the thickness direction. In cas of measuring the pressure of winding work, the pressure-sensitive paper 9 is placed between the double-divided through spacer 10 to be inserted for covering the windings 2aW2c. Besides, a jack 6 is placed between a winding ring 4 and winding cap metal 5a arranged on the spacer 10 to mount the winding in axial direction for the confirmation of the homogeneity of the mounting pressure distribution of the winding by the pressure-sensitive paper 9. Then, the pressure-sensitive paper 9 is removed together with the spacer 10 to mount the winding by the fixed pressure on the jack 6 again. Thereafter, an interval piece is arranged between the winding ring 4 and cap metal 5a to reduce the pressure for the removal of the jack 6.