What are the installation precautions for low-voltage frequency converters?
1. Safety Precautions
1. Firstly, it requires a certain level of electrical expertise, familiarity with the job site, understanding of equipment conditions, and professional electrical skills.
2. Identify the voltage level of the equipment (such as low voltage AC380V), whether it is low voltage equipment, and verify if the equipment is energized.
3. When working on live circuits, wear insulating shoes, insulating gloves, or stand on a dry wooden board. Tools used must have complete insulation protection and should not touch different phases of power sources or metal structures.
4. During power-off operations, obtain a work permit, perform power-off, voltage check, install grounding wires, and set up safety barriers or hang safety warning tapes.
5. For low-voltage installations or line work, require at least two people to perform the task and designate a dedicated supervisor.
2. Installation Precautions
1. Installation Environment
(1) Ambient Temperature
The inverter, like other electronic devices, has specific requirements for ambient temperature, typically between -10°C and +40°C. Due to the high-power electronic components inside the inverter, they are highly sensitive to operating temperatures. For safety and reliability, it is best to keep the temperature below 40°C; between 40°C and 50°C, derating is required, reducing the rated output current by 1% for every 1°C increase. High environmental temperatures and significant temperature fluctuations can greatly reduce the insulation properties of the inverter, affecting its lifespan.
(2) Humidity
The relative humidity around the inverter should be ≤95% (no condensation). Depending on the site environment, desiccants and heaters may need to be placed inside the inverter cabinet.
(3) Vibration and Shock
During operation, avoid vibration and shock. The inverter consists of many components assembled through welding and screw connections. Mechanical vibrations or shocks can cause welds, screws, and connectors to loosen or detach, leading to poor electrical contact or even short circuits. Therefore, besides enhancing the mechanical strength of the control cabinet and keeping it away from vibration and impact sources, anti-vibration rubber pads should be added externally, and buffer rubber pads should be installed between internal components and mounting plates.
Regular inspections and maintenance should be conducted after some time of operation.
(4) Electrical Environment
- Prevent Electromagnetic Interference: The main body of the inverter includes power modules and control systems' hardware and software circuits, which can malfunction due to electromagnetic interference. To prevent this, measures against EMI should be taken, such as keeping input power lines, motor output lines, and control lines separate; critical signal lines should use shielded cables with 360° grounding.
- Prevent Input Overvoltage: Power electronic components within the inverter are very sensitive to overvoltage. Measures should be taken to prevent input overvoltage, especially in environments with fluctuating power supplies.
(5) Altitude
The inverter can output rated power when installed below an altitude of 1000m. Above 1000m, output power decreases. For example, at an altitude of 4000m, the output current is only 40% of that at 1000m.
(6) Other Environments
- Avoid installing inverters where raindrops or condensation may occur;
- Prevent dust, lint, and metal shavings from entering;
- Avoid installation in areas with oil contamination and high salt content;
- Stay away from radioactive materials and flammable substances.
2.2 Installation Method and Heat Dissipation Handling
Due to power losses during operation, the inverter's temperature rises. Roughly speaking, each 1kVA of inverter capacity results in approximately 40W to 50W of power loss. Therefore, consider heat dissipation methods when installing the inverter.
(1) Wall-Mounted Installation: Generally, the inverter can be directly mounted on walls. Ensure vertical installation and maintain distances from surrounding objects: sides greater than 100mm, top and bottom greater than 150mm. Install a baffle above the exhaust port to prevent debris from blocking the airflow.
(2) Cabinet Installation: In dusty, humid environments, or when additional peripheral components are needed, cabinet installation is recommended. This method provides good shielding against radiation, dust, and moisture. Single-unit installations should have a top-mounted cooling fan, while multi-unit installations should be side-by-side or separated by partitions.
3. Inverter Wiring
3.1 Main Circuit Wiring
(1) Three-phase AC input terminals (R, S, T): Connect these terminals via circuit breakers to the three-phase AC power supply without considering phase sequence. Do not connect three-phase AC power directly to the inverter's output terminals.
(2) Three-phase AC output terminals (U, V, W): Connect these terminals correctly to the motor. If the motor direction is incorrect, swap any two of (U, V, W) or adjust settings. Do not connect capacitors or surge absorbers to the output terminals.
(3) DC Reactor Connection Terminals (DC+, P+): These terminals connect to a power factor correction DC reactor. Remove the shorting link before connecting the reactor.
(4) Braking Unit Connection Terminals (DC+, BK): Small power inverters usually have built-in braking units (external braking resistors required), while larger models require external braking units and resistors.
(5) DC Power Input Terminals (DC+, DC-): External braking unit DC input terminals connect to the positive and negative poles of the DC bus.
(6) Ground Terminal (PE): Leakage currents increase with carrier frequency. Ground both the inverter and motor for safety.
3.2 Precautions
- Ground resistance should be less than 10Ω, and grounding cable size depends on inverter power.
- Do not share ground wires with welding machines or other power equipment.
- If neutral and ground are shared, consider laying separate grounding cables.
- For multiple inverters, connect them individually to earth; do not form grounding loops.
3.3 Control Circuit Terminal Wiring
- Control circuit cables should use twisted shielded wires to prevent interference.
- Separate control cables from main circuit cables by at least 100mm; avoid parallel runs and cross only perpendicularly.
- Shielding should be connected to the common terminal (COM) but not the PE terminal.
- Digital control lines should be twisted pairs with minimal spacing and grounded at the inverter’s grounding terminal E, with a maximum length of 50m.
- Single-point grounding for weak signal circuits; do not use grounding wires for signal transmission.
4. Inverter Lightning Protection
Inverters include lightning absorption networks to protect against transient lightning strikes. However, in areas with frequent lightning activity, additional protection is necessary:
- Install dedicated lightning arresters at the power input.
- Buried steel pipes for dedicated grounding protection 20m away from the inverter.
- Ensure proper lightning protection for control rooms if using cable-fed power to prevent lightning-induced damage.
Sunye Electric Co., Ltd. (Changsha Sunye Electric Co., Ltd. was established in 2010; Shenzhen Sunye Electric Co., Ltd. was established in 2002) is a national high-tech enterprise integrating R&D, manufacturing, and sales of inverters, industry-specific all-in-one machines, servo drives, and new energy products.
Sunye Electric owns independent intellectual property rights, with products passing inspections and certifications by national authoritative institutions and obtaining multiple software copyrights and IP certificates. It invests heavily every year in researching new technologies and developing new products, with many patents and software copyrights granted. Core platform technologies include construction hoist drivers, high-performance vector inverters, servos, and permanent magnet synchronous motor controls. Low- and medium-voltage inverters and servo drives are widely used in industries such as lifting equipment, stone processing, HVAC, machine tools, metal products, wire and cable, plastics, printing and packaging, textile and chemical fibers, building materials, metallurgy, coal mining, municipal services, and automotive applications. Guided by the philosophy of "innovation, technology, and strength," and driven by the corporate spirit of "unity, progress, pragmatism, and innovation," the company adheres to the business principle of "honesty and excellence, mutual benefit and coexistence." With a quality policy of "implementing total quality management and continuous improvement to pursue zero defects," Sunye Electric is committed to providing premium products to customers across various industries.
Address: Sunye Electric Industrial Park, No. 669 Xinsheng Road, High-Tech Zone, Changsha City
Tel/Fax: 0731-89932666 0731-89932688
Business Phone: 400-0755-731
Technical Support: 400-0755-731
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