Table of Contents
The uninterrupted operation of lifting crane pulley, which includes a large number of different electrical systems, depends very much on their stable and continuous operation. The complex of electrical pulley crane, which is equipped with modern cranes, is necessary to continue to work without failures and accidents in any situation, regardless of whether there are temperature and humidity changes. Such systems must be vibro- and dust-resistant, capable of supporting various modes of operation.
Both large factories and small enterprises not always can afford the costs associated with the purchase of advanced models of handling crane pulley system. Most often, the domestic industry exploits obsolete load-lifting units.
How can it be, if the opportunity to purchase a new crane is missing, and the old one ceases to cope with the accelerating and more complicated production process? In this case, the owner of the load-lifting unit should consider the possibility of updating the electrical systems of the crane mechanism. One of such solutions can be the modernization of the crane electric drive with the help of the system of frequency inverters. In this case, a modern frequency converter provides control of an AC induction motor with a squirrel cage rotor.
The main advantages of the latest technologies: nautical terminology
Among the advantages of shifting of the operation of crane’s electrical equipment into this system are:
- impact loads on the drive are reduced to zero and, as a result, the operating time of the crane mechanisms increases
- dynamic loads in the elements of the kinematic chain become less likely. This will reduce the cost of overhauling mechanical components
- the consumed reactive power of the equipment will become less, which will positively affect the amount of electricity consumed – it will decrease. This will be facilitated by the lack of starting surges and the elimination of rheostats in speed control
- short-lived relay-contactor equipment ceases to be a necessity, which leads to a decrease in the frequency of failures in the operation of the crane electric drive
- instead of electric motors with a phase rotor, equipment with a squirrel-cage rotor is used, all the components meet modern requirements and standards, which increases the reliability of the electrical systems
- acceleration and braking of the electric motor occurs without jerks, smoothly
- speed and acceleration of the operation of crane mechanisms can be adjusted, and this can be done with a sufficiently high accuracy
- encoders (shaft rotation sensors) provide feedback, which allows maintaining a constant motor speed in the variable load mode
- a rigid mechanical characteristic (maintaining a constant speed) allows the brake to smoothly stop before starting another cycle
- the increase/decrease of the load does not affect the speed
- due to the absence of jerks during the change of modes, the service life of the mechanical parts of the lifting unit increases
- current protection, as well as protection against overheating of the motor and converter from overload, excessive voltage deviations, phase failure, phase-to-phase short-circuit, phase-to-ground closure is the most effective
- the absence of overloads and smooth operation of crane mechanisms allows preventing potential loss of a cargo
- the braking resistor performs dynamic braking, thereby ensuring the “landing” speed of the system
- the crane operator becomes more comfortable and safer to operate the equipment
- the crane’s downtime caused by electric drive malfunctions is reduced to 4 hours per year.
The best decision
Such a solution makes it possible to use them as a part of load-lifting mechanisms to implement the following applied functions:
- brake operation adjustment, suitable for travel and lifting drives, as well as checking the brake condition
- control and regulation of the end of the boom by limit switches
- there is no reduction in the speed of operation of the machines, even under the condition of a small load or an empty hook
- selection of cargo ropes according to their strength parameters
- load balancing, master-slave circuit, torque control
- one frequency converter can be used in multi-motor crane drives thanks to the multi-motor/multi-configuration function
- checking compliance with the parameters of the set speed, rotation in the reverse direction, overload, etc.
In particular, the use of a variable-frequency drive has opened the following technical possibilities:
- there appeared a function of controlling the high-speed mode from “0” to and above the nominal value
- the acceleration and deceleration processes are carried out smoothly
- in starting, operating, and emergency modes the current level does not exceed expected values
- the service life of the mechanical and electrical parts of the crane is substantially extended
- the equipment demonstrated stable operation at temperatures from -40 to +40°.
The payback period of installed components on average is:
- for installation cranes – 170 working days
- for construction cranes – 340 working days.
Taking into account the great exploitation resource of the lifting equipment, such terms seem quite real.
One of the main advantages of modern frequency-controlled electric drives is the preservation and multiplication of the funds invested in them. First, the money spent on their acquisition is returned within 3-5 years. After that, over the next 15-20 years, the owner receives a net profit. Secondly, these investments never leave the enterprise limits.