The continuous improvement of the industrial level and the development of power electronics technology make the quality level of the machine is also improving. According to relevant data, the power consumption of the high-voltage motor used in China accounts for 30% of the national power generation. Therefore, the transformation of the high-voltage motor frequency control can save the power, and the product market has a great prospect.

　　In order to achieve the purpose of electrical energy saving and process optimization, the high voltage inverter should be noted in the project planning:

　　First, the high voltage motor characteristic experiment and the technical specification revision

　　When a general motor is supplied with a power supply from a frequency converter, the voltage and current harmonic weights at the output end of the frequency converter will increase the loss, decrease the efficiency and increase the temperature of the motor. The loss of stator and rotor is mainly caused by the loss of copper, iron and additional loss. Meanwhile, the rotor copper consumption is the most obvious, because the asynchronous motor always rotates in a state with a slip of nearly 1, so the rotor copper consumption is very large. In general asynchronous motors, in order to improve the starting performance of the motor, the skin effect of the rotor makes the actual impedance added, and then increases the copper consumption.

　　On the other hand, because of the high voltage motor coil, and distributed capacitance between when higher harmonic voltage input, the voltage between the coil is not uniform, such a long time repeated role to form one part of the stator winding insulation damage, and then attack coil aging, in terms of general asynchronous motor insulation structure, this is unbearable. It is impossible to achieve absolute symmetry in the electromagnetic circuit of other motors, so the various harmonic weights contained in the output power of the frequency converter will interact with the inherent spatial harmonic weights in the electromagnetic circuit to form various electromagnetic pulsations.

　　Together, the motor is in the operating state of frequency constant adjustment, it is easy to have mechanical resonance with the mechanical part of the motor, forming the damage of the mechanical part of the motor.

　　Therefore, in the frequency conversion speed regulation transformation project, in order to prevent the frequency conversion speed regulation system from appearing the above problems in the operation, the technical planning must consider the technical cooperation with the high voltage motor manufacturers, the related characteristics of the motor speed regulation experiment, from the beginning to revise the original motor technical specifications.

　　Key to type selection and laying requirements of power cables

　　Because the connection between the output end of the frequency converter and the motor is connected by the cable attachment method, and the capacitance to the ground exists in each phase of the line, the capacitance current on the line is not equal during operation. If the cable is provided with a long interval, and there is a high harmonic current in the line, once the single-phase grounding occurs, the arc triggered by the fault capacitor current will be extinguished for too long, which will make the cable at this end get hot and form non-fault insulation.

　　Therefore, in the transformation project of frequency conversion speed regulation, regarding the output power cable, considering the three-phase symmetry and shielding on the cable structure, add the cable section properly and lay the length not exceeding the limit value of 100m. If the original output power cable is unshielded or the flow margin of the section is less than 2, replace the power cable that meets the requirements. The power cable should be laid separately from the control cable and signal cable to prevent other signals from being disturbed by the magnetic field caused by high harmonics in the power cable.

　　Basic requirements for the operating environment of the frequency converter

　　Because the inverter part of the high voltage inverter selects high voltage IGBT and other power equipment, its on and off frequency is greater than 100HZ, easy to form high harmonic current, so that the frequency conversion equipment will have a certain amount of heat during operation. Be in commonly the coping of inverter ark all has platoon fan, the quantity of heat inside its cabinet discharges indoor, this makes indoor environment temperature rises ceaselessly, the firm operation that still can affect each equipment inside ark after all.

　　Therefore, in the water plant project planning in the general frequency control equipment alone set in the frequency control room, indoor must be installed spare air conditioning equipment, control the indoor environment temperature in the frequency converter required scale, with ventilation doors and Windows, when necessary to select a special duct for forced ventilation and cooling.

　　High voltage power supply system export circuit breaker control technology perfect

　　The high voltage side of the transformer used in the frequency control equipment should be directly connected to the switch cabinet in the high voltage system, but the maintenance scale of the switch cabinet is only the short circuit between the power supply line and the low voltage side of the transformer, and the fault of the converter should be completed by the detection and maintenance system of the converter itself. When the frequency converter malfunctions to declare a trip signal, the circuit breaker should be firmly acting trip.

　　However, the general circuit breaker high voltage switch cabinet internal tripping circuit break or dc control power supply disappeared, inverter just appear fault (require circuit breaker tripping), tripping coil has lost power, circuit breaker rejected action, thus forming the power equipment within the inverter damage.

　　Therefore, the circuit breaker with under-voltage tripping coil is selected in the planning. Once the tripping circuit is broken or the control power supply disappears, the circuit breaker shall first automatically tripping to maintain the safety of the inverter equipment.