This paper discusses the disturbance of the electromagnetic performance of coreless linear synchronous permanent magnet actuators due to an electrically conductive material in the air gap which is part of the cooling system. Time-varying magnetic fields in the air gap give rise to induced eddy currents in the conductive material. These induced currents disturb the magnetic fields of the current-carrying coils and the magnet array. Different measurements are presented differentiating between the disturbance of the coil field and the magnet field. The effects of these disturbances on the motor performance are discussed. Suggestions are given to make changes to the shape of the conductive material to minimize these disturbances.