Estimator and estimator system

An estimator system comprising:

• a plurality of estimators each configured to estimate a temperature of a stator coil of an electric rotary machine, the electric rotary machine configured to be cooled by cooling oil,
• the plurality of estimators each including
• an electronic control unit configured to calculate a state quantity by using an input signal and a relational expression that expresses a target model, and
• a correction signal measurement sensor configured to measure a correction signal for correcting the state quantity,
• each electronic control unit being configured to
• output a value for correcting the state quantity based on the correction signal, and
• change the relational expression that expresses the target model in accordance with an oil flow related value that relates to a change of flow of the cooling oil,
• the correction signal measurement sensor being arranged such that the correction signal measurement sensor is in contact with a metal member that includes a coil conductive wire that constitutes the stator coil, a terminal connected to the coil conductive wire, and a power line connected between the coil conductive wire and the terminal, at a point on which no cooling oil drops;
• and
• selection means configured to select a maximum temperature of the stator coil from among the temperatures of the stator coil, respectively estimated by the plurality of estimators.