Introduction to the principle of electric screw machine

One. The electrical control system of the microcomputer controller electric screw air compressor is the key system of the electric screw compressor. Its main function is to reduce the voltage and reduce the starting current when the three-phase asynchronous motor (capacity is greater than 10KW) is started, so as not to generate excessive power in the power supply line. Voltage drop to reduce the impact on the grid.

The system has the following characteristics:

1. Function and technical parameters

①Switch quantity: 9 channels of switch input, 10 channels of relay switch output;

②Analog: two pt100 temperature inputs, two 4-20mA transmission inputs, two three-phase current inputs (with CT); ③phase sequence input voltage: three-phase 380V;

③The working current of the controller: 220V, 50Hz, 20VA;

④Phase sequence protection: When the protector detects the wrong phase, the display will alarm and cannot start;

⑤ The main controller has five protection functions for both the main motor and the fan motor, which are stall protection, short circuit protection, phase loss protection, unbalance protection, and overload inverse time protection features;

⑦ Temperature protection: When the actual temperature detected is greater than the set temperature, the action time is less than 2S; ⑧ Output relay contact capacity: 250V 5A; contact life 5000000 times; ⑨ Current display error is less than 1.0.

2. Controller wiring terminal The display and the main controller are connected by a communication cable. 23, 24, and 25 are phase sequence input terminals; 7, 9 are exhaust temperature input terminals; CT1 is the main motor transformer; CT2 is the fan motor transformer 32 is the common terminal of the output relay COM1; 27 controls the main contactor (KM1); 28 controls the star contactor (KM3); 29 controls the delta contactor (KM2); 30 loads the solenoid valve; 31 controls the motor; 34 controls the discharge Valve; 37 operating instructions; 42 for grounding; 43, 44 for 220V power supply.

two. Control principle The controller has a self-check for 3 seconds after it is powered on, and it cannot be started by pressing the start button. After the self-check is over, press the start button to start the host; if there is a failure, press the emergency stop button. The starting process of the host is: KM3 and KM1 are powered on → Y-shaped starting state → delay time is up (Y/△ conversion time), KM3 is de-energized (KM2, KM3 interlock), KM2 is powered on → motor is started in △-shaped. After the motor starts to the △ state, after a period of delay, the loading solenoid valve is energized and the air compressor starts to load. When the air pressure rises above the set high limit pressure (unloading pressure value), the loading solenoid valve loses power and the air compressor runs empty. During the empty time, if the pressure does not drop to the low limit pressure, the controller will automatically stop the motor Work, realize the automatic shutdown of the empty car for too long. In order to prevent frequent start control, press the stop button, and the empty car will stop for too long. When a fault stop causes the motor to stop, the motor cannot be started immediately, and a delay is required. The controller counts down the time display window to display the remaining delay time (such as 90 seconds) in various shutdown states, and the motor can only be started when the delay time is zero.