US 12,294,320 B2
Electric motor control device
Yu Zhang, Tokyo (JP); Yuuri Takano, Tokyo (JP); and Hideto Takada, Tokyo (JP)
Assigned to HITACHI INDUSTRIAL EQUIPMENT SYSTEMS CO., LTD., Tokyo (JP)
Appl. No. 18/271,290
Filed by Hitachi Industrial Equipment Systems Co., Ltd., Tokyo (JP)
PCT Filed Dec. 23, 2021, PCT No. PCT/JP2021/048060
§ 371(c)(1), (2) Date Jul. 7, 2023,
PCT Pub. No. WO2022/269950, PCT Pub. Date Dec. 29, 2022.
Claims priority of application No. 2021-106115 (JP), filed on Jun. 25, 2021.
Prior Publication US 2024/0072701 A1, Feb. 29, 2024
Int. Cl. H02P 21/14 (2016.01); H02P 25/022 (2016.01); H02P 27/06 (2006.01)
CPC H02P 21/14 (2013.01) [H02P 25/022 (2013.01); H02P 27/06 (2013.01)] 8 Claims
OG exemplary drawing
 
1. A electric motor control device for an electric motor, the electric motor control device comprising:
a converter circuit that converts a first AC voltage to a DC voltage,
an inverter circuit the DC voltage from the converter circuit to a second AC voltage and supplies the second AC voltage to the electric motor,
an inverter controller that control the inverter circuit,
a current detector that detects a current flowing in the electric motors and
a power calculation unit that is configured to:
estimate a temperature of the electric motors from the current detected by the current detector,
calculate a resistance value of the electric motors from the temperature estimated,
calculate a machine output from a q-axis detected current value and a detected speed value,
calculate a copper loss from the resistance value calculated,
calculate a first difference between the copper loss at a start time and an end time,
calculate a second difference between the machine output at the start time and the end time, and
output an alarm signal when either the first difference or the second difference exceeds a respective threshold value.