1 Introduction

A bridge crane is a kind of bridge crane that runs on an elevated track with a bridge frame. It is commonly known as a crane and is widely used in indoor and outdoor warehouses, factories, docks, and open-air storage yards.Ordinary bridge cranes are generally composed of lifting trolleys, bridge operating mechanisms, and bridge metal structures.The lifting trolley is composed of three parts: the lifting mechanism, the trolley operating mechanism and the trolley frame. See Figure 1. 

The driving methods of the crane's electric operating mechanism can be divided into two categories: one is centralized driving, that is, a motor is used to drive the long drive shaft to drive the active wheels on both sides; the other is independent driving, that is, the active wheels on both sides are each driven by a motor.Small and medium-sized bridge cranes mostly use a “three-in-one” drive mode that combines brakes, reducers and motors. Ordinary bridge cranes with large lifting weights often use universal couplings for easy installation and adjustment. Coupling. 

The electric operating mechanism consists of three basically independent drag systems.①car drag system: Drag the entire crane to move “laterally” along the workshop (subject to the operator's sitting direction).②car drag system: drag the hooks and heavy objects to move “vertically” along the bridge.③Hook drag system: Drag heavy objects to move up and down when they are lifted or lowered. 

Compared with the control of the lifting mechanism, the bridge crane has relatively low requirements for the control of the inverter in terms of cart drag and trolley drag, so this article focuses on the application of Cool Horse Q9000 series inverter in the control of the lifting mechanism.The operation of the lifting mechanism has the characteristics of large inertia and four-quadrant operation. Compared with other transmission machinery, the inverter has more demanding safety and performance requirements.Cool Horse Q9000 series inverter is a frequency converter specially designed for crane loads, which has the following characteristics: ① It has full vector control.At a low frequency of 0.5HZ, even if there is no speed feedback link, it can provide a starting torque of 150% of the rated torque.②The four-quadrant operation.The energy feedback device can be configured to realize four-quadrant operation, and the dynamic response is good.③Constant torque characteristics.In the full speed range, it has constant torque characteristics.

2 Application design of Q9000 inverter in lifting mechanism 

In order to ensure the design conditions, the project conducted actual tests on the applicability of the Q9000 series inverter crane project.The test site is a factory specializing in the production of lifting equipment in Zhuzhou.Test configuration: The motor model is YZR200L-8 (winding motor), the power is 15kW, the rated input voltage is 380V, the rated input current is 34.6A, the number of motor poles is 8 poles, the rated frequency is 50HZ, the rated speed is 712rpm, and there is no encoder.The brake adopts the method of solenoid valve and is controlled by a 3-phase 380V power supply.Taking into account the possibility of overload operation in the future and the stability of long-term operation, Delta Q9000-1544 inverter was selected for testing.

2.1 Main circuit design

Since the power of the QMA inverter is greater than 15KW, there is no built-in brake unit for the model level, so an external recommended brake unit CDBR4030 is optional.The model number assigned on the brake resistor manual is 5000W/27.2ohms. Taking into account the brake performance and the heat dissipation performance of the resistor when the weather is hot, the selection principle of brake resistor specifications is based on two aspects: the equivalent resistance value is maintained at the recommended minimum resistance value, and the power selection is about 2 times the recommended power.Since there are BR1K5W040 (1500W/40 ohms) specifications in stock, 12 BR1K5W040 resistors are selected and connected in series and parallel. The equivalent resistance is 30 ohms and the equivalent power is 18KW.The actual connection diagram is shown in Figure 2.See Figure 3 for the electrical wiring diagram of the QMA Q9000 series high-performance vector inverter.

Figure 2 Electrical schematic diagram of external brake unit CDBR4030

Figure 3Q9000 series inverter electrical wiring

2.2 Inverter SVC control method
　　Vector control without speed sensor (also known as SVC control method, sensorless VC) can obtain performance close to closed-loop control, while eliminating the need for speed sensors and having low maintenance costs.Compared with traditional V/Hz control, vector control without speed sensor can obtain improved low-speed operating characteristics, and the speed adjustment ability under variable load can also be improved. At the same time, high starting torque can be obtained, which has obvious advantages in the starting of high friction and inertial loads.It is precisely because of these drive characteristics that this control technology has gradually become the choice for general constant torque drive applications. 

QMA Q9000 series frequency converters provide SVC control mode, which can well meet the need for full load (or even overload, usually very short running time) operation when starting on lifting equipment.The SVC control method can obtain excellent dynamic and static characteristics from the basic principle, but the premise is to obtain accurate motor parameters.The relevant parameters of the Q9000 inverter related to the motor are shown in Table 1.

Table 1 Q9000 inverter motor related parameters

2.3 Gate timing control

Recommended brake opening/closing signal setting

The signal of the brake opening/closing, depending on the control mode used, please use the output signal of the inverter recommended below.

Note: The brake opening/closing signal, please do not set it to running in any control mode (set to 00.）

Note 1: Take the parameter setting when using the multi-function contact output terminal (RA-RC) as an example.

Note 2: Without PG vector control, the parameter P4-01 is usually set to 1.0~3.0Hz;

        When the setting is too low, the motor's starting torque is insufficient and it is easy to slip during start-up.Please be sure to set the value at 51-09 (the most

        Low output frequency) and the value of P4-02 in the figure below.

        When the setting is too high, it is prone to high current shock during start-up.

        The falling edge of the frequency detection signal can be adjusted by P4-02 (0.1~0.5Hz).When the slip phenomenon occurs when it stops，

        Please adjust P4-02=0.1Hz.

2.4 Inverter parameter design
（1）The parameters are restored to the factory value：

（2）Set motor parameters：

Note: For 52-03 no-load current, it can be obtained in several ways: 1.The motor parameters are calculated through the dynamic test of the inverter (the motor must be dragged away from the load to run), but because this lifting equipment cannot be dynamically tested, this method cannot be used; 2.Obtained on the motor nameplate; 3.Running at no load in VF mode, check the output current of the inverter; 4.Query the manual.

（3）Motor parameter measurement：

Main menu

Easy-tuning

　After the motor parameter measurement is completed, check the motor parameter：

（4）The adjustment control mode is (current control) mode：

（5）Adjust parameters：

（6）Adjust the control point of the mechanical brake：

Since the mechanical brake is controlled by a contactor, and the contactor power supply is 220V, relay control is used, and RA/RC normally open contacts are selected.

2.5 Load operation

Use the above parameters for load operation.The state of the bus voltage when operating at 0-50HZ with 6 tons of load： 

(1) Not running state.500VDC; the voltage is 480VDC when rising and starting; the maximum voltage is 730VDC during falling； 

(2) The state of the output current when operating with an 8-ton load.The maximum current is 70A during rising and starting, the maximum current is 56A during falling, and the current is 29A during stable operation.

3 Concluding remarks

Under load, the starting current is maintained within 3 times the rated current range (the overload current range of the QMA Q9000 inverter is 3 times the rated), which can provide sufficient starting torque; the maximum bus voltage is maintained at the set value of 730VDC during the load drop, which ensures that the inverter does not have an OV alarm; the T2-01=37 function judgment condition adopts a comprehensive judgment of frequency and current to ensure that there is no slip hook phenomenon under load.After testing, it can meet the requirements of long-term safe and stable operation of project lifting equipment.