Application of Maikeno KE300A VFD in Elevator

2022-12-08

Device selection

According to the parameters of the motor (30KW/380V) of the hoist on site, this device belongs to constant torque load. Based on its working characteristics, it needs to be selected for the second gear amplification to ensure safe, stable, and fast operation of the system. The recommended configuration is as follows:

Number	Model	Rated power	Rated voltage	Rated current	Quantity
1	KE300A-045G/055P-T4	45KW	380V	90A	1

Control method

The main circuit wiring is very simple. Connect the three-phase power supply to the input terminals R, S, and T of the inverter, and connect the output terminals U, V, and W of the inverter to the U, V, and W terminals of the corresponding hoist motor.
Due to the large inertia impact and regeneration energy generated by the hoist, a brake resistor must be added to consume the regeneration energy. The details are shown in the following figure:

正转运行 Positive rotation operation

反转运行 Reverse rotation

段速1 Segment speed 1

段速2 Segment speed 2

段速3 Segment speed 3

频率水平检测FDTI输出 Frequency level detection FDTI output

故障信号输出 Fault signal output

欧姆 Ohm

制动单元 Brake unit

刹车电阻 Brake resistor

电机 Motor

The hoist control system gives the inverter a switch signal for positive and negative rotation: when the D1 terminal and the COM terminal are closed, the inverter starts rotating positively, and when disconnected, the inverter stops; when the D2 terminal and the COM terminal are closed, the inverter starts to rotate negatively, and when disconnected, the inverter stops;
The hoist control system gives the inverter a switch signal for three-speed operation: When the D3 terminal and the COM terminal are closed, the inverter runs at the first speed; when the D4 terminal and the COM terminal are closed, the inverter runs at the second speed; when the D3 and D4 terminals and the COM terminal are closed, the inverter runs at the third speed; When the D5 terminal and the COM terminal are closed, the inverter runs at the fourth speed; when the D3, D5 terminals and the COM terminal are closed, the inverter runs at the fifth speed; when the D3, D4, and D5 terminals and the COM terminal are disconnected, the inverter runs at the first speed;
The inverter gives the hoist control system a normally closed "fault output" switch signal. When the inverter fails, the motor can immediately brake and lock;
The inverter gives the hoist control system a normally open "frequency level detection FDT1 output" switch signal. Only when the frequency of the inverter reaches the set value can the tower crane control system release the hoisting motor brake to ensure that there is no "slip hook" phenomenon.

Problems encountered and solutions during debugging

When the hoist is descending, the motor does negative work, which leads to a high main circuit voltage of the inverter, so a braking unit and a braking resistor must be added to release the energy generated by the hoist during the descent process. For KE300A series inverter, the braking unit is built-in for power below 18.5KW, so only a braking resistor needs to be added.

Parameter P9-04 is the threshold value for braking, and the factory default value is 130%; the standard busbar voltage of the inverter is 540V, and 540V*130% = 702V

That is to say, when the bus voltage of the inverter reaches 702V, the braking valve will open. If the inverter still has overvoltage alarms (E-05/E-06/E-07), the P9-04 parameter can be appropriately reduced to lower the threshold for opening the brake.

Since the hoist brakes for a long time during the entire descent process, the braking resistor should be appropriately selected to be larger, otherwise the temperature of the resistor will be very high, causing abnormal system operation.

Conclusion

The application of MICNO KE300A inverter on the hoist effectively solves the control problem of the hoist. After adopting the inverter control, the system control becomes simpler, and the control system has multiple protections, which ensures the comfort and safety of the brake release at the moment of opening, no "overrun" phenomenon during ascent, and no "weightlessness" phenomenon during descent, making the system more safe and reliable.