Frequency converter selection(2)
1. Selection of cabinet structure of frequency converter
The box structure of frequency converter should be adapted to environmental conditions, including temperature, humidity, dust, PH, corrosive gas and other factors that must be considered. The following types of structures are commonly available for users to choose.
1) Opening IPOO type itself has no case, which is suitable for the screen, disc and rack installed in the electric control box or electrical room, especially when multiple frequency converters are used intensively.
2) Closed type IP20 is applicable for general use, with a little dust or temperature or humidity.
3) Sealed type IP45 is suitable for the environment with poor industrial field conditions.
4) Closed IP65 is applicable to occasions with poor environmental conditions, water, dust and certain corrosive gases.
2. Determination of converter capacity
Reasonable capacity selection is an energy-saving measure. According to the existing data and experience, there are three simple methods.
1) Determining the actual power of the motor. First, the actual power of the motor is measured to select the capacity of the converter.
2) Formula method. When one inverter is used for multiple motors, it should be satisfied at least one motor starting current that should be considered to avoid over-current tripping of the converter.
3) Motor rated current method frequency converter. Frequency converter capacity selection process is actually a process the best match between the inverter and motor. Relatively safe is the most common, which also makes the converter capacity that is greater than or equal to the motor rated power but want to consider the actual power of the motor in the actual match what differ with rated power. Usually, selecting equipment capacity is big but the actual ability is small. Therefore, according to the actual power of the motor, it selects frequency converter, which is reasonable, avoiding to choose the frequency converter which is too large and increased investment. For the light load type, the inverter current should be generally selected as 1.1N (N is the motor rated current), or as the maximum motor power which is indicated in the product by the manufacturer in accordance with the output power rating of the inverter.