With the continuous development of frequency conversion technology, frequency converters are being used more and more widely. In recent years, the price of high-voltage frequency converters has decreased along with the continuous development of frequency conversion technology, creating favorable conditions for the large-scale promotion and application of high-voltage frequency converters . This article introduces high-voltage frequency converters from the following aspects.
What is a high-voltage frequency converter?
What are the different types of high-voltage frequency converters?
What are the speed regulation and energy-saving principles of high-voltage frequency converters?
What are the differences in the production environment between high-voltage frequency converters and low-voltage frequency converters?
Definition and principle of high voltage frequency converter
High-voltage frequency converter: Medium and large capacity frequency converters used to drive AC motors above 1kV are called high-voltage frequency converters.
In China, the three common standard voltages are 3kV, 6kV, and 10kV.
Internationally, the four common standard voltages are 3.3kV, 6.6kV, 11kV, and 4.16kV (North America).
1. Speed Regulation Principle
The expression for the speed of an AC asynchronous motor is:
n=(1-s)60f/p
s—slippage;
p — Number of pole pairs of the motor;
f — Motor operating frequency.
Conclusion: If the frequency f of the AC current applied to the stator winding of the asynchronous motor is changed smoothly, the rotor speed n of the asynchronous motor can be adjusted smoothly.
2. Energy-saving principle
When high-voltage frequency converters are used for energy-saving purposes, they are mostly designed for square torque loads such as ordinary fans and water pumps.
Conclusion: When the output shaft speed decreases by 20%, the output shaft power decreases by 49%.
QH characteristic curves of fans and water pumps
1) Comparison of energy saving between power frequency and variable frequency regulation methods
2) Energy efficiency comparison under various adjustment methods
Classification of high voltage frequency converters
[1] Based on whether there is a DC component in the intermediate stage, frequency converters can be divided into AC-AC converters and AC-DC-AC converters;
[2] According to the nature of the DC component, frequency converters can be divided into current-type and voltage-type converters;
[3] According to whether there is an intermediate low-voltage circuit, it can be divided into high-high frequency converters and high-low-high frequency converters;
[4] According to the number of output levels, frequency converters can be divided into two-level, three-level, five-level and multi-level converters;
[5] According to voltage level and application, frequency converters can be divided into general-purpose frequency converters and high-voltage frequency converters;
[6] According to the clamping method, frequency converters can be divided into diode clamping type and capacitor clamping type, etc.
High-voltage frequency converter production process
1. No-load test
• Automated one-click operation, eliminating the need for manual intervention and improving testing efficiency.
• Automatic fault alarm handling.
• Automatically generated test reports with traceable data.
• Safety protection, isolation protection during testing
• Automatic discharge, safe and reliable
2. Aging test
• Full load and aging are performed simultaneously to meet the temperature rise test requirements under full load.
• 100% simulated real-life scenario.
• Fully automated testing avoids human error and saves test records in real time.
3. Incoming component inspection
Key components undergo full inspection and high-voltage testing;
Professional temperature testing equipment; key components are 100% screened one by one.
Professional pressure resistance testing equipment;
4. Order monitoring
Online order processing, quality control, and tracking of abnormal progress;
Visualization of workstation management;
Information sharing among departments;
Statistical reports are generated automatically, and the data is traceable.
5. Assembly and debugging
Fully physical isolation protective fence;
The whole machine test includes wiring check, low voltage test, withstand voltage test, high voltage test, no-load test, and rated current load test.
Full-voltage and full-current full-load tests were conducted on the entire machine.
Dielectric testing is conducted according to international electrical testing standards to ensure the insulation performance of the equipment (100% whole machine 10000~27000V dielectric test) and prevent insulation problems from occurring at the customer's site.
6. Full load test
It meets the factory full-load test requirements for high-voltage frequency converters below 3MW, greatly improving product quality.
Connect to field equipment
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