Patent ID: 9714968
Date: 2017-07-25
CPC Classifications: G01R

Claim:
1. A surface-potential distribution measuring device for measuring a surface potential of an electric-field-reduction system that is applied along a longitudinal direction of a stator coil end which is a stator coil end unit of a stator of a rotating electric machine, the device comprising: a laser light source to emit a laser beam; a Pockels crystal to receive the laser beam emitted from the laser light source via a first end surface of the Pockels crystal in an incident direction; a mirror whose surface is provided at a second end surface that is the opposite side of the Pockels crystal from the first end surface and which reflects the laser beam that enters the Pockels crystal via the first end surface in a direction opposite to the incident direction; a photodetector having a band to follow a high frequency component of an inverter pulse voltage, a photodetector to receive the laser beam reflected by the mirror, and to detect light intensity of the laser beam corresponding to an output voltage that is a difference in potential between the first end surface and the second end surface of the Pockels crystal; a holding and mounting part to hold and to move at least the Pockels crystal; a voltage correction database to store input voltage-output voltage characteristics showing relation between different input voltages and the output voltages of the Pockels crystal when various input voltages are applied to a back side of the mirror; and a calculation unit to identify an input voltage corresponding to a testing output voltage as a surface potential of the electric-field-reduction system based on the input voltage-output voltage characteristics stored in the voltage correction database when the back side of the mirror is disposed with a unit of a surface of the electric-field-reduction system as a test point and when the output voltage of the Pockels crystal that is output as voltage is applied to the stator coil is regarded as the testing output voltage, wherein the Pockels crystal is formed in such a way that a size of a cross section of the Pockels crystal that is perpendicular to an axial direction changes along the axial direction, and the holding and mounting part includes: