1, an overview of
countries using the AC power supply, whether for home or for the plant, its voltage and frequency are 200V / 60Hz (50Hz) or 100V / 60Hz (50Hz), and so on. Typically, the fixed voltage and frequency alternating current is converted into alternating current voltage or variable frequency device called “drive.” In order to produce a variable voltage and frequency, the device is first necessary to convert AC power to DC (DC).The direct current (DC) is converted into alternating current (AC) means the scientific term for the “inverter” (inverter).Since the main means changing voltage or frequency converter generating device called “inverter”, so that the product itself was named “inverter”, namely: the drive, the drive can also be used for household electrical appliances. Inverter home appliances not only have the motor (such as air conditioning, etc.), as well as fluorescent lamps and other products. Inverter for motor control, can change both voltage and frequency can be changed. But the drive for fluorescent lamps primarily for regulating the power supply frequency. Device battery (DC) generated alternating current used on the car also “inverter” in the name for sale. Inverter works have been widely used in various fields. Such as computer power supply, in this application, the drive for inhibiting reverse voltage, power outages and frequency fluctuations supply.
2. Why is the rotational speed of the motor can be freely changed?
r / min motor rotation speed unit: number of times per minute rotation can also be expressed as rpm, for example: 4-pole motor 60Hz 1,800 [r / min], 4 -pole motor 50Hz 1,500 [r / min], the rotation speed of the motor of the same frequency as proportion.
Motor herein referred to as AC induction motors, industrial motors most used are the motor of this type. AC induction motor (hereinafter referred to as the motor) of the rotation speed of approximately determined depending on the number of poles and frequency of the motor. Depending on the operating principle of the motor motor pole number is fixed. Since the pole is not a continuous numerical value (a multiple of 2, for example, the number of poles 2,4,6), so the discomfort and change the value to adjust the speed of the motor. In addition, the frequency of the electrical power supply of the motor, so that the values can be adjusted on the outside of the motor and then supplied to the motor, the rotational speed of the motor so that it can be freely controlled. Therefore, for the purpose of controlling the frequency inverter, motor speed control device is used as the preferred device. n = 60f / p, n: synchronous speed, f: power frequency, p: number of motor poles, changing the frequency and voltage is the optimal motor control method. If you change the frequency only, the motor will be burned. Especially when the frequency is reduced, the problem is very prominent. To prevent motor burn accidents, while changing the frequency inverter must also change the voltage, for example: in order to make the rotation speed of the motor is halved, the output frequency of the inverter must be changed from 60Hz to 30Hz, then the output voltage of the inverter it must be changed from 200V to about 100V. ? For example: In order to make the rotation speed of the motor is halved, the output frequency of the inverter must be changed from 60Hz to 30Hz, then the output voltage of the inverter must be changed from 200V to about 100V. If you want to use the correct drive, you must carefully consider the heat problem. Inverter failure rate with increasing temperature from rising index. Life with increasing temperature dropped from the index. Ambient temperature 10 degrees, the service life of the drive halved. Therefore, we should pay attention to the heat problem ah! When the drive is operating, the current flowing through the drive is great, the heat generated by the drive is very large, it can not ignore the impact of heat generated.
Typically, the drive is installed in the control cabinet. We must understand that a drive is about how much heat can be estimated using the following formula: = calorific approximation inverter capacity (KW) × 55 [W] here, if the drive is constant torque load capacity registration (flow capacity of 150% × 60s) If the drive has a DC reactor or AC reactor, and also in the cupboard, then the heat will be even greater. Reactors installed in the drive side or above measured better. Then you can use the estimate: drive capacity (KW) × 60 [W] as each inverter manufacturers of hardware are similar, so the formula can for each brand of products Note: If the braking resistor words, because the braking resistor a large amount of heat, it is best to install the best location and the drive to isolate, as installed in the cabinet above or beside the like.According to increase the calorific value generated in the cabinet, should be appropriate to increase the size of the cabinet. Therefore, if the size of the control cabinet to minimize the heat value is generated in the cabinet must make to minimize. If the drive is installed, the heatsink portion of the inverter to the outside of the control cabinet, the drive will be 70% of the amount of heat released to the outside of the control cabinet. Due to the large capacity drive has a great amount of heat, so the more efficient large capacity inverter. You can also use the separator plate body and radiator are separated so that the heat sink does not affect the inverter. This effect is also very good. Inverter thermal design are to be mounted vertically based, sideways put the heat will deteriorate! Cooling fan on the inverter power in general slightly larger, are equipped with a cooling fan. It also recommends the installation in the control cabinet cooling fan outlet. Inlet to add filter to prevent dust from entering the control cabinet. Note that the control cabinet and inverter fan is to be, and who can not substitute anyone.