Slip-dependent motor model

• US 10,298,168 B2
• Filed: 05/11/2017
• Issued: 05/21/2019
• Est. Priority Date: 07/07/2016
• Status: Active Grant

• Current Assignee: Schweitzer Engineering Laboratories, Incorporated
• Original Assignee: Schweitzer Engineering Laboratories, Incorporated
• Inventors: Donolo, Marcos A.
• Primary Examiner(s): Luo, David
• Application Number:
  US15/592,636
• Publication Number:
  US 20180013375A1
• Time in Patent Office: 740 Days
• Field of Search: 318717, 318716, 318700
• CPC Class Codes: G01R 31/34 Testing dynamo-electric machines
• CPC Class Codes: G06F 30/15 Vehicle, aircraft or watercraft design
• CPC Class Codes: G06F 30/20 Design optimisation, verification or simulation optimisation, verification or simulation of circuit designs G06F30/30
• CPC Class Codes: H02P 29/66 Controlling or determining the temperature of the rotor
• CPC Class Codes: H02P 6/20 Arrangements for starting H02P6/08 takes precedence
• CPC Class Codes: H02P 6/34 Modelling or simulation for control purposes

Abstract

The present disclosure pertains to systems and methods configured to monitor and protect an electric motor during startup using a motor model. The motor model parameters may be calculated using measurements taken during a calibration start of the electric motor. The measurements may include slip, stator current, stator voltage, frequency, and/or other electrical or physical parameters. In some embodiments, the motor model parameters may be calculated by minimizing the difference between a measured slip and a calculated slip. The motor model may comprise a variety of parameters used to determine operation parameters of the motor during the startup. In one specific embodiment, the motor model may determine a thermal capacity used (TCU). The TCU may be compared to a threshold value to determine whether protective action is necessary.

Claims

1. A system configured to generate a slip-dependent motor model to monitor and protect an electric motor during a motor start, comprising:

an electrical measurement input to monitor at least one electrical condition of electrical energy supplied to the electric motor;

a slip input configured to monitor a measured slip of the electric motor;

a processor in communication with the electrical measurement input and the slip input and configured to;

generate a motor model based on the at least one electrical condition and the measured slip during a calibration motor start;

measure the at least one electrical condition of the motor during a subsequent motor start;

determine a calculated slip of the motor during the subsequent start based on the at least one electrical condition and the motor model; and

,

implement a control action based on the calculated slip and the motor model;

wherein the motor model comprises a representation of a standstill rotor condition resistance, a rotor resistance at synchronous speed, and a stator resistance.

2. The system of claim 1, wherein the electric motor comprises a synchronous motor.

3. The system of claim 1, wherein the at least one measured electrical condition comprises one of an electric current, and an electric voltage.

4. The system of claim 1, wherein the processor is further configured to:

calculate a thermal capacity used (TCU) of the electric motor during the subsequent start using the thermal model and the at least one measured electrical condition;

compare the TCU to a threshold; and

determine that the TCU exceeds the threshold;

wherein the protective action comprises interrupting the flow of electrical energy supplied to the motor.

5. The system of claim 4, wherein the processor is further programmed to determine the TCU using the calculated slip.

6. The system of claim 1, wherein the at least one measured electrical condition comprises an electric current and the motor model is further configured to determine a calculated slip during the subsequent start based on the electric current.

7. The system of claim 1, wherein the processor is further configured to determine a ratio of running rotor resistance to a standstill rotor condition resistance and wherein the motor model is at least partially based on the ratio.

8. The system of claim 1, further comprising a shaft-mounted sensor in communication with the slip input.

9. The system of claim 1, wherein the representations of the standstill rotor condition resistance, the rotor resistance at synchronous speed, and the stator resistance are determined by minimizing a difference between a modeled slip function and the measured slip.

10. A method for generating a slip-dependent motor model for monitoring and protecting an electric motor during a motor start, comprising:

monitoring at least one measured electrical condition of electrical energy supplied to the electric motor;

monitoring a measured slip of the electric motor;

generating a motor model based on the at least one measured electrical condition and the measured slip during a calibration motor start, the motor model comprising a representation of a standstill rotor condition resistance, a rotor resistance at synchronous speed, and a stator resistance;

measuring the at least one electrical condition during a subsequent motor start;

implementing a control action based on the calculated slip and the motor model.

11. The method of claim 10, wherein the electric motor comprises a synchronous motor.

12. The method of claim 10, wherein the at least one measured electrical condition comprises one of an electric current, an electric voltage, and a frequency.

13. The method of claim 10, further comprising:

calculating a thermal capacity used (TCU) of the electric motor during the subsequent start using the motor model and the at least one measured electrical condition of electrical energy;

comparing the TCU to a threshold;

determining that the TCU exceeds the threshold.

14. The method of claim 10, further comprising determining a calculated slip during the subsequent start based on the at least one electrical condition of electrical energy.

15. The method of claim 10, wherein the at least one measured electrical condition comprises an electric current and calculating a slip during the subsequent start based on the electric current.

16. The method of claim 10, further comprising determining a ratio of running rotor resistance to a standstill rotor condition resistance and wherein the motor model is at least partially based on the ratio.

17. The method of claim 10, wherein the threshold accounts for motor losses following the subsequent start.

18. The method of claim 10, further comprising minimizing a difference between a modeled slip function and the measured slip to determine the representations of the standstill rotor condition resistance, the rotor resistance at synchronous speed, and the stator resistance.

19. A system configured to generate a slip-dependent motor model to monitor and protect an electric motor during a motor start, comprising:

an electrical measurement input to monitor at least one electrical condition of electrical energy supplied to the electric motor, the electrical condition comprising an electric current;

a slip input configured to monitor a measured slip of the electric motor;

a processor in communication with the electrical measurement input and the slip input and configured to;

generate a motor model based on the at least one electrical condition and the measured slip during a calibration motor start;

measure the at least one electrical condition of the motor during a subsequent motor start;

determine a calculated slip of the motor during the subsequent start based on the at least one electrical condition and the motor model, wherein the electrical condition comprises an electric current; and

,

implement a control action based on the calculated slip and the motor model.

20. A system configured to generate a slip-dependent motor model to monitor and protect an electric motor during a motor start, comprising:

an electrical measurement input to monitor at least one electrical condition of electrical energy supplied to the electric motor;

a slip input configured to monitor a measured slip of the electric motor;

a processor in communication with the electrical measurement input and the slip input and configured to;

determine a ratio of running rotor resistance to a standstill rotor resistance using the measured slip;

generate a motor model based on the at least one electrical condition and the ratio during a calibration motor start;

measure the at least one electrical condition of the motor during a subsequent motor start;

determine a calculated slip of the motor during the subsequent start based on the at least on electrical condition and the motor model; and

,

implement a control action based on the calculated slip and the motor model.