1. Speed rotor resistance
(1) cam controller asymmetric rotor resistance of the program used for 5 ~ 10t general overhead crane control circuit, through asymmetric rotor resistors in series, changing the inherent characteristics of the motor to achieve the purpose of speed curve. This program structure is simple, low cost, but the speed varies greatly, the intermediate speed is unstable. Strictly speaking, can not be called governor program, which can only improve the motor starting characteristics.
(2) The master controller to control the motor speed control of single-phase and reverse decline
The program used for 1 6 ~ 50t general overhead crane control circuit, which is characterized by reversible asymmetric circuits. Increase in tandem with each block starter motor rotor resistance; dropped first gear is reverse braking, only to return in the first block of the second gear when the work, and the load must be greater than the rated load of 56; dropped the second block is a single phase brake, mainly for light load drop; decline third gear as regenerative braking. The program structure is simple, low cost, but can not increase speed, the mechanical properties of very soft, great rate of speed change, speed can not be long-running.
2. Self-excited brake force governor
Circuit is characterized by reversible asymmetric circuit, fall off the motor when the three-phase AC power to the two-phase stator winding pass into the early formation of the air gap magnetic field excitation current, motor overhauling load under the action of the cutting rotor air gap magnetic field, induced currents and braking torque. The rectified and then fed into the stator windings, the excitation current to increase the air gap magnetic field enhanced braking torque increases. Braking torque equal to the potential energy function of the load torque on the motor shaft, the rotor current, self-excitation current is kept constant, stable operation of the motor. When changing the rotor resistance, the motor speed changes, cranes rise equivalent series resistance starter and rotor speed. The program in the heavy falls, with medium-speed and high-speed gear, energy-efficient and more reliable. But when you can not get a stable increase in low-speed, light-load can not control, operation convenient.
3. Hydraulic plunger speed
Rotor speed access through the transformer type power hydraulic brake push rod motor stator, the rotor due to motor voltage and frequency with its speed and change, so when the motor speed increases, the rotor voltage and frequency reduced accordingly, reduced power f hydraulic brake force also decreases the corresponding braking torque increases, the motor speed decreases. Conversely, the motor speed decreases, the braking torque is reduced, the motor speed increases. When the load torque, variable torque and braking torque generated by the motor power balance, stable operation of the motor, so as to achieve the purpose of speed. The program, through access to high-value resistors rotor system rise and fall will be eligible for a more stable speed. But it can only get a low-speed, middle-speed characteristic soft, and must make changes to the mechanical parts of the crane can be used.
4. Eddy current brake governor
Motor and eddy current brake coaxial link motor when the motor speed drops off, eddy current brake is energized. Brake gate, the load drops and the eddy current brake braking torque issue. When the load torque and braking torque equilibrium eddy current brake, the load to obtain a stable low decline. When the motor is in the middle of steepest descent reverse electric state, eddy current brake field winding is energized, the motor system has been artificially properties and synthesis of eddy current brake torque curve. When the load torque and the torque balance synthetic motor speed when the speed dropped down} as regenerative braking state. Rising electric motor runs in the forward state, the governor is basically the same principle and drops. The program rise and fall can be speed, speed ratio up to 1: lO, middle and low speed can be obtained. But the speed is changed greatly, intermediate speed can not be long-running, the line is more complex, you must make changes to the mechanical parts of the crane can be used.
5. Stator voltage control thyristor
Each phase series motor three-phase power into a group of anti-parallel thyristors, by changing the thyristor conduction angle control motor stator voltage to achieve speed. This program speed range up to 1:10, speed change rate of less than 5, the rise and fall can be governor, with some prospects. But the program is more complex, difficult to debug.
6. VVVF
AC variable speed inverter is the ideal medium speed solution, but using the crane is still rare, mainly because of the crane starting torque; crane drops motor is in regenerative braking; drive higher prices, etc. reasons caused. With the advancement of science and technology, LSI technology, computer technology, PWM technology, vector conversion technology and energy feedback technology has been successfully applied in the inverter, the inverter used in the crane has matured.
(A) Works
As shown in the drawings, the starter contactor KM when energized, the inverter is energized, the DM signal indicator lights, R, s power and frequency control separated from the main circuit wiring to make protective circuit is activated, keep the drive abnormal output signals for easy maintenance and failure analysis. SA master controller turned up a gear when, K3, K5 pull, drive forward signal STF, low-speed signal RL connected to the common terminal SD. Then there is the starting frequency inverter output, the motor does not rotate. Because the brake is not open, but not enough to avoid starting torque slip hook, K1 off of zero protection and abnormal output protection (drive B, C contacts as abnormal output contacts). When the output frequency reaches the set value 3Hz brake release frequency, the brake release current detection and maintained asked 0.3s after setting, the inverter output signal through RUN terminal requires opening the brake. Namely RUN terminal through the SE guide, K8 was electric contact closure. K9 suction units, brake motor M2 is energized. STOP terminals connected simultaneously with the SD captive. Brake motor is energized to open, the braking time is 0.3s, the drive to the starting frequency 3Hz drive motor begins to turn. In time, the frequency inverter accelerates to the set value changes continuously, can be seen cranes lifting speed of change is also continuous. With the SA from low gear to high-speed switching. K5, K6, K7 were grouped into seven different status input inverter, so that the output of seven different frequencies resulting in seven different lifting speeds stopped, SA back to zero after each block, the inverter output frequency at deceleration time decreases continuously. When the output frequency is equal to the variable neck brake engage frequency (6Hz) time. Mechanical brake close signal obtained through the RUN terminal. RUN and SE Open, K8, K9 power, STOP terminal and SD disconnect the brake starts closing. Drive through O. 5s after the stop output, M1 motor stops. Down the principles and rises works the same reference frequency control loop
(2) Features
Frequency control using flux vector control technology or high torque boost technology that solves the crane starting torque, low speed high torque output and load changes fierce giant problem; asked deceleration setting resolves crane system moving the impact of changes in the speed of the crane continuous, stable operation; signal or frequency using the frequency reaches the brake opening and closing detection signal, only the motor output torque is greater than the load torque, the brake was opened, to solve the problem of sliding the hook using the power feedback technology to run the motor in the fourth quadrant regenerative energy is converted into 50Hz AC feedback network, protect the drive does not breakdown; main control loop separately and reliably grounded to avoid strong electrical weak signal of the inverter thousand scratch.
Frequency control is one of the best option crane speed, speed ratio up to 1:10 or more, can realize stepless speed regulation. Speed mechanical characteristics of each block is very hard, heavy low starting and running stable and reliable, acceleration and deceleration time settings so that each block starting and braking speed is quite stable. With high control accuracy, the design of fault display, analysis and parameter monitoring functions, easy to use and maintain, and easy to implement automatic control and remote control.
