Frequency conversion bridge crane
Frequency conversion speed regulation design of bridge crane
1, bridge crane frequency control hardware selection
(1) the choice of variable frequency motor
A, hoisting mechanism variable frequency motor should meet: (where: P-motor capacity (kw); G-rated weight (kg), 125% overload capacity should be considered; v- rated linear velocity (m / min); η – mechanical efficiency).
B, the moving mechanism of the motor should meet: (where: P – motor capacity (kw); u – mobile resistance (kg); V – rated speed (m / min); In the case of outdoor, the resistance to windage and the resistance to increase due to the inclination (horizontal degree) of the moving path must also be included in the moving resistance.
(2) the choice of frequency converter
When selecting the capacity of the inverter of the overhead crane, the output current of the inverter is usually used as the selection condition. The nameplate output current I1 of the frequency converter shall meet the following conditions: and /
K0-safety factor, repeat the short-term work of the general situation to take 1 ~ 1.1; K1-maximum load factor (Ie-motor rated current; I0-motor maximum operating current for the static load current and dynamic load current sum; , That is, the required maximum torque and motor rated torque ratio; K2-margin factor, the general take 1.2; K3- inverter overload capacity factor, see product manual.)
(3) braking resistor and brake unit selection
Braking resistor resistance calculation basis: the inverter motor regenerative energy must be fully absorbed by the braking resistor, that meet R = V ² / Pe × Kc; and brake the brake current selection unit, which meet (where: R-system K-braking frequency, in the bridge crane to take 0.2 to 0.4; K-feedback of the mechanical energy of the resistance value; V-braking unit DC operating point voltage, generally take 700V; Pe-motor rated power; Conversion efficiency, the general take 0.7).
(4) Programmable controller (PLC) choice
In the overhead crane, because the control agencies of the stalls are generally 5 files, then the total number of PLCs required for each institution is generally 19 to 20 points. The total number of points required for a bridge crane of three organizations is about 60.
(5) Other electrical components according to the relevant standards to choose, not in detail here.
2, bridge crane frequency control of the electrical diagram design
Is to Chuan inverter, for example, the main description of the bridge crane frequency control section of the electrical diagram design. Bridge crane hoist mechanism of the frequency control of the electrical schematic diagram shown in Figure 2. Hoisting mechanism The frequency conversion motor is equipped with a rotary encoder, connected with the speed card installed in the inverter to form the speed closed-loop control. The control points of S1 ~ S7, SC, MA, MB, M1, M2 on the frequency converter and the control circuit of the control motor fan running contactor K7 and the brake contactor K8 are respectively connected with the input, output and power point of the selected PLC Connection, through the PLC internal program operation, to achieve the hoisting mechanism frequency control closed-loop control. Between the inverter power supply input terminals (R, S, T) and the power supply, there are earth leakage circuit breakers Q1 and AC reactors. The leakage circuit breaker Q1 capacity of the inverter rated current of 1.8 times the induction current of 30mA or more, you can detect dangerous high-frequency leakage current to the human body to prevent accidents; and its AC reactor and inverter DC reactor can effectively improve the power side of the power factor, reduce the interference to the outside world.
3, the bridge crane frequency control program design
Bridge crane frequency control program design is actually selected PLC within the program design. PLC programming is generally used ladder diagram or instruction table in two ways for program design. Bridge crane frequency control PLC program in two parts: the operation of control procedures and communication interface program. General bridge crane frequency control main program is running control procedures, and for the communication interface program only when the PLC is equipped with a touch screen will be involved. Bridge cranes each organization’s movement control procedure basically by the electrical protection, the stall control, the brake and the electrical machinery fan movement program segment is composed. Among them, the stall control is the stall change of the indoor linkage console of the bridge crane driver, and the multi-step speed command of the inverter is controlled by the program running in the PLC, so that the output frequency of the inverter changes with the gear position according to preset The frequency changes.
3,Installation and Debugging of VVVF of Bridge Crane
Bridge crane frequency control cabinet installed in the cabinet, the inverter from top to bottom or other components from the cabinet or the distance should be more than 120mm, left and right from the cabinet or other components of the distance should be more than 30mm, and the inverter and PLC most Good in the same cabinet, to avoid the impact of each other. Inverter and PLC control circuit wiring should be shielded cable, as far as possible with the power line separation alignment. Inverter and PLC grounding using C kind of grounding, and welding machine, power equipment, such as ground separation, the wiring should be as short as possible.
- Before the commissioning of all equipment, line wiring inspection, measurement of electrical wiring in the process of transport and installation damage, as well as the existence of power grid phase loss phenomenon; (2) the installation of the bridge crane, (3) After power on the inverter, the motor will be jogged by the control panel on the inverter to see if the inverter can be operated in the same way. Its direction of rotation is correct; then select the appropriate self-learning motor, the motor self-learning. (4) Set the parameters corresponding to the selected control mode and other corresponding parameters (see the specific inverter manual for the specific settings). (4) Set the corresponding parameters of the selected control mode and other corresponding parameters (For details, refer to the manual of the selected inverter) , And to determine all the equipment power are no exception, the bridge crane no-load debugging. (5) no-load debugging is good, bring the rated load to full load debugging. At full load commissioning, the appropriate change in the inverter acceleration and deceleration time parameter values, so that acceleration and deceleration time adjustment to achieve the best value. If the hoist mechanism is running at full load, there is a clear slide hook imagination, you need to adjust the braking parameters within the drive.