Generally, users of air compressors with power above 250kW will choose high voltage power supply to drive, especially the air supply system of multiple air compressors will choose a higher proportion. High-voltage power supply air compressors use 3kV, 6kV, 10kV, etc. 3kV voltage is rarely used in China. It is the high-voltage power supply standard in the United States and Japan. It is usually used when imported equipment is introduced (such as Shanghai Baosteel). The high-voltage power supply voltages commonly used in presses are 6kV and 10kV.

Why do most of the main motors of high-voltage power compressors use high-voltage power instead of the commonly used 380v power supply? Let's take a look at the benefits of high-voltage power compressors driven by high-voltage power. We know that the instantaneous current when the motor starts is its rated current. For example, a 25OkW motor starts at 380V and its rated current is 450A. If the starting multiple is 7, the starting current is 450 * 7 = 3150A. Such a large current has a very large impact on the power grid, which will greatly harm the user's power grid quality. In addition, the voltage loss of the wires connected to the high-voltage motor will also be great. Assume that the motor wire impedance is 0.02Ω. When the power supply voltage is 380V, the instantaneous power supply voltage loss is 0.02 * 3150 = 63V. At this time, there is only 317V left from the grid voltage to the motor terminal. The motor starts at a low voltage, resulting in current. The increase will cause the motor temperature to rise, which will cause the motor insulation to age to damage for a long time. The motor power is the ratio of the product of voltage and current. The power of the 380V motor is increased to a certain level. The large current will limit the allowable carrying capacity of the wire and it is difficult to make high power. For this reason, high-power motors use high-voltage power to drive nature. Becomes a better choice.

Of course, the 380V high-power motor will not be started directly. In the air compressor industry, star delta start, soft starter start, and frequency conversion start are usually used. The inverter is started by changing the frequency and voltage. The U / F ratio is constant. For this reason, the magnetic flux is basically constant and the starting torque is large, so the starting current is small. Of course, the inverter also has the advantages of energy saving and constant pressure air supply. . The soft starter changes the starting voltage through the conduction angle of the thyristor (the adjustment of the voltage is stepless), that is, a step-down starting method is used to reduce the starting current of the motor. The star triangle is a simpler step-down startup, which is realized by the conversion of three contactors. The voltage at startup is 220V, and the operating voltage after startup is 380V. When the air compressor is started, it is not really no-load. There is a micro hole in the intake valve. It needs to establish an initial pressure and at least it needs to provide the cylinder energy of the intake valve during loading, so it is larger than the no-load current. To this end, the starting current multiple of the soft starter is about 2.5 times (450 � 2.5 = 1125A), and the starting current of the Star Delta is about 3.5 times (450 � 3.5 = 1575A). It can be seen that the actual starting current is still not small, and there is still a large amount of power on the power grid. A certain impact.