Five Reasons of Cranes Use Frequency Control of Motor Speed

Frequency control of motor speed can be used in most of the applications of electric motor, because it can provide accurate speed controlling, so you can easily control the electric crane's rise and fall, variable speed operation of the mechanical transmission. Frequency conversion application can greatly improve the machine efficiency (variable speed does not depend on mechanical parts), at the same time can be more energy saving than the original fixed speed running motor. The following listed five reasons for using frequency control of motor speed illustrating the basic understanding of inverter application which has become increasingly popular:
First, to control starting current of the crane's motor
When the motor is started directly by power frequency, it will produce a seven to eight times rated current of the motor, the current value will greatly increase the electric stress of motor winding and produces heat, reducing the lifetime of the motor. While the frequency control of motor speed can realize speed starts at zero speed and zero voltage (also can add appropriate torque increase).Once the relationship of frequency and voltage is built, frequency converter can work with load according to the V/F or vector control driving. Using frequency control of motor speed can greatly reduce the starting current, increase endurance of the winding group, the most direct benefit for the user is the maintenance costs of the motor will be further reduced, the service life of motor is increased accordingly.
Second, to reduce voltage fluctuation of the power line
When a electric mechanic frequency is starting, current surge is sharp increased, at the same time, the voltage will be large swinging, the range of the voltage drop is depend on the starting of the motor size and power capacity of the distribution network. Voltage drop will lead to operation failure and abnormal tripping of some power supply voltage sensitive equipment which is in the same electric network, such as PC, sensors, proximity switch and contactor, etc, all these parts may go wrong. But if we using frequency control of motor speed, motor speed can start step by step even on a zero frequency and zero voltage, will eliminate the voltage drop at the most extent.
Third, the starting power is lower
Motor power is proportional to the current and voltage of the motor, the power consumption directly by power frequency electric will be much higher than that of frequency conversion start power. Its distribution system has reached to the highest limit in some using conditions, the surge generated by its direct starting motor power frequency will have a significant impact to other users in the same electric internet. If we use the frequency converter for motor start-stop, it won't produce such similar problems.
Fourth, controllable speeding up function
Frequency control of crane's motor speed can start at a zero speed and speeding up evenly according to user’s needs, and we can choose the speeding up curve freely (linear acceleration, s-shaped or automatic acceleration).But the motor or some shaft, gear, other mechanical parts which are connected together starting by power frequency can produce severe vibration. This vibration will lead to sharp mechanical wear and tear, to reduce the lifetime of crane's mechanical components and motor. In addition, frequency conversion starting can be used in similar filling line, to prevent the bottle spill or damage.
Fifth, the traveling speed is adjustable
Using frequency control can optimize the technological process, and speed can be changed according to the process quickly, also can achieve speed change through the remote control PLC or other controller.