For a frequency converter to operate normally, two basic conditions are required: a frequency signal and an operating signal. The purpose of using a frequency converter is to change the motor speed by altering its output frequency. So how do we adjust the frequency converter's output frequency? The key is to change the signal that the frequency converter provides; this signal is called the "frequency setpoint signal."
Several ways to obtain the frequency signal
1. Operator Panel Setting: Operator panel setting is the simplest way to set the frequency of a frequency converter.
Users can directly change the frequency setting of the frequency converter using the potentiometer, numeric keys, or up/down keys on the operator panel. The biggest advantage of operator panel setting is its simplicity and convenience, while also providing monitoring functionality, displaying the current, voltage, speed, etc., of the frequency converter in real time.
If the numeric keys or up/down keys are selected for setting, the accuracy and resolution are very high because it is a digital setting. If the potentiometer on the operator panel is selected, it is an analog setting, with slightly lower accuracy, but it is highly practical because it does not require additional wiring like an external potentiometer for analog input.
2. External potentiometer setting: Frequency is adjusted by using a potentiometer input from outside the inverter.
3. Multi-function input terminal setting: The inverter's set frequency value is changed through its multi-function input terminals. These terminals can be connected to external buttons, PLCs, or relay outputs. Two or more terminals in the inverter's function input terminals can be configured for frequency setting after function settings.
Inverter Operating Conditions
1. The operating temperature of inverters is typically 0–40℃ or -10–50℃. Ensure proper ventilation of the inverter cabinet. The ambient temperature test point should be approximately 5mm away from the inverter.
2. The relative humidity around the inverter should be 5%–90%, with no condensation. High humidity can reduce electrical insulation and cause corrosion of metal parts. If the inverter must be installed in a high-humidity location, the inverter cabinet should be as sealed as possible. To prevent condensation when the inverter is stopped, a convection heater may be required.
3. The area around the frequency converter should be free of corrosive, explosive, or flammable gases, dust, and oil mist. Explosive or flammable gases around the frequency converter can cause fires or explosions, as relays and contactors inside the converter are prone to sparking. Corrosive gases will cause corrosion of metal parts, affecting the long-term operation of the frequency converter. Dust and oil mist will accumulate inside the frequency converter, leading to reduced insulation. For forced air-cooled frequency converters, clogged filters will cause abnormal temperature rises inside the converter, resulting in unstable operation.
4. The vibration resistance of frequency converters varies depending on the model. Vibration exceeding the converter's allowable value will cause loosening of fasteners and malfunctions of moving parts such as relays and contactors, often leading to unstable operation. For machine tools, ships, and other applications where vibration is foreseeable, the vibration of the frequency converter should be considered.
5. The altitude of frequency converter application sites is mostly specified to be below 1000m. High altitudes result in lower air pressure, which can easily lead to insulation damage. There are no direct regulations regarding the insulation of frequency converters used at altitudes above 1000m. However, the withstand voltage decreases by 5% at 1500m and by 20% at 3000m. Additionally, the thin air at high altitudes reduces heat dissipation and cooling efficiency, necessitating careful attention to temperature rise. Starting from 1000m altitude, the permissible temperature rise decreases by 1% for every 100m increase. When using frequency converters at altitudes above 1000m, the power rating should be appropriately increased.
6. Frequency converters must not be installed near sources of electromagnetic radiation.
The above information covers frequency adjustment for frequency converters. We hope this information is helpful.
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