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Ground insulation on-line monitoring method for variable frequency motor based on leakage current time-domain characteristics

A technology for ground-insulated and variable-frequency motors, which is used in motor generator testing, short-circuit testing, and dielectric strength testing. It can solve problems such as the inability to provide degradation location information, and achieve the effect of monitoring the severity of degradation.

Pending Publication Date: 2022-04-15
HEBEI UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

There is a clear difference between the transient current response spectrum of a healthy motor and an aged motor. To better characterize the insulation state, it is necessary to quantify the high-frequency difference, and the switching transient monitoring method also cannot provide information on the location of the degradation.

Method used

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  • Ground insulation on-line monitoring method for variable frequency motor based on leakage current time-domain characteristics
  • Ground insulation on-line monitoring method for variable frequency motor based on leakage current time-domain characteristics
  • Ground insulation on-line monitoring method for variable frequency motor based on leakage current time-domain characteristics

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0042] The test platform set up to verify the proposed method is as follows: image 3 shown. The test motor used in this test platform is a 3kW variable frequency motor, and the inverter is controlled by dSPACE. In order to simulate the degradation of the insulation to the ground, RC adjustment circuits with different impedances are connected between the stator winding and the ground. For test conditions and motor parameters see Figure 8 , where the insulation resistance and insulation capacitance are the parameters of the RC regulating circuit. During the test, the test conditions of the variable frequency motor system remained unchanged.

[0043] The schematic diagram of the test platform setup is as follows: image 3 shown. Install a current transformer at the input end of the motor to measure the ground leakage current, and install three sets of voltage transformers to measure the phase voltage. In order to eliminate the error caused by noise and DC bus voltage fluc...

Embodiment 2

[0051] It is also possible to use the leakage current oscillation period T c To realize the online monitoring of the frequency conversion motor to the ground insulation degradation position, the monitoring process includes:

[0052] Step 1. Establish the periodic component P of the leakage current c expression for:

[0053] In the formula, t is the test time of leakage current signal, R g Insulation resistance to ground, C g is the insulation capacitance to ground, L s is the stator inductance, R s is the stator resistance, x is the degradation position of the ground insulation;

[0054] Step 2: Establish the leakage current oscillation period T based on the periodic component Pc c expression for:

[0055] In the formula, R g Insulation resistance to ground, C g is the insulation capacitance to ground, L s is the stator inductance, R s is the stator resistance, x is the degradation position of the ground insulation;

[0056] by T c It can be seen from the expr...

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Abstract

The invention discloses a variable frequency motor ground insulation on-line monitoring method based on leakage current time-domain characteristics, and the method comprises the steps: carrying out the on-line monitoring of the ground insulation degradation phase, the ground insulation degradation position and the ground insulation degradation severity of a variable frequency motor through employing the initial oscillation amplitude, oscillation period and decay time of leakage current; therefore, the function of ground insulation on-line monitoring of the variable frequency motor is realized. The beneficial effect of the invention is that favorable basis and basis are provided for maintenance and use of the variable frequency motor.

Description

technical field [0001] The invention relates to the technical field of on-line monitoring of variable frequency motors, in particular to an on-line monitoring method for the ground insulation of a variable frequency motor based on time-domain characteristics of leakage current. Background technique [0002] Variable frequency motors have been widely used in industrial applications, and their failure can lead to huge financial losses and safety problems. As we all know, the most common faults of AC motors are stator insulation faults, bearing faults and rotor faults. According to survey statistics, about 30%-40% of motor failures are related to stator insulation. For variable frequency motors, high du / dt and repetitive pulse voltages greatly accelerate insulation degradation, so monitoring stator windings to ground insulation is critical in this case. [0003] Typically, insulation degradation is a long-term development that may last for many years. Insulation degradation ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R31/12G01R31/34G01R31/52
Inventor 牛峰王云龙黄少坡吴立建黄晓艳方攸同李奎
Owner HEBEI UNIV OF TECH
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