Causes and methods of influence of inverter harmonics on motor
Since all commercially available motor protectors are all designed to protect the motor by collecting current or voltage changes, the motor bearings are damaged due to various reasons, and the rotor is eccentric, which causes the motor to broom and burn the motor. The problem is that these protectors are not able to protect the function, because only after the motor broom, the winding burns out and shorts, this kind of protector will be activated, but it is too late; so far there is no smart Products that protect motor bearings; many users can only artificially monitor or periodically patrol the temperature changes of the test bearings to artificially protect some large motors. There are two drawbacks to this approach: 1. It increases the workload of the personnel, increases the personnel costs of the enterprise, and fails to care for all motors. 2, is the time limit for manual testing, there is no time limit within 24 hours, then if the bearing is damaged during the non-testing time, the rotor confidence, the motor broom, the accident of burning the motor can not be avoided. When the motor is driven by the inverter, the life is greatly shortened. In severe cases, the stator winding is damaged in a few months. The resulting shutdown has caused huge losses to the company.
The reason for the motor damage is that the inverter generates a very high peak voltage on the stator winding of the motor. The amplitude of the spike voltage exceeds the insulation strength of the winding, resulting in winding damage. The amplitude of the spike voltage will be more than three times the rated operating voltage of the inverter. For example, for inverters with a rated voltage of 380V, the amplitude of the spike voltage exceeds 1200V. This spike voltage impacts the stator windings of the motor thousands of times per second and can quickly cause damage to the stator windings.
In addition, the inverter will also generate bearing current in the bearing of the motor. The bearing current will flow through the bearing for a long time, which will cause the bearing to burn. The smaller the power, the more easily the stator winding will be damaged. The larger the power, the more the bearing easily damaged.
The SVA (Spike Voltage Absorber) spike voltage absorber is an innovative motor protection product for the above problems. The SVA is installed in parallel on the power input end of the motor, which can effectively absorb the peak voltage and bearing current generated by the inverter on the motor, so that the motor and the frequency converter are perfectly matched.
Compared to traditional du/dt filters or sine wave filters, SVA has the following advantages:
1) It is easy to install in parallel with the motor;
2) There is no voltage drop, no torque reduction, and no control of the inverter on the motor;
3) Small size, light weight and high cost performance, especially for high-power motors, the advantages are more obvious;
4) Convenient selection, independent of the motor speed and carrier frequency, no need to match the motor with specific power;
5) Intelligent control, automatically adjust the absorbed power according to the carrier frequency and cable length to ensure the best effect;
6) The panel display information is rich, and the working status of the absorber can be known at any time;
7) Built-in insurance, automatically out of the system when the fault occurs, and the fault status is displayed on the panel;
8) Fully sealed design for harsh industrial field environments.
