Emotron - crane drives with frequency inverters

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Company Emotron has been dealing with application of frequency inverter on crane drives since 1990. During this time already has been developed several type ranges of frequency inverters equipped with special crane software. Thanks to longtime experience Emotron AB belongs among the world top companies in this field.

EMOTRON VFX 2.0 are, thanks to the direct torque control, mainly used for operation with the crane drives. These inverters are always equipped by the Crane set 2.0. It contains from crane card CRANE 2.0, crane interface CI 230 VAC and the ENODER 2.0 card for conection of IRC sensor. Frequency inverters in this configuration operating as autonomous controlling system of crane drive. That means, that except of standard functions of speed control ensuring logical links of inputs, brake control and control the status of the drive.

Advantages of crane drives with frequency inverters:

Crane at night
  • Not only big energy saving, but also savings in term of mechanical part of drive wear-gears, brakes, and also as crane itself.
  • Continuous speed control from 0 up to maximum without reduction of motor torque.
  • Continuous diagnostics of motor.
  • All operating parts (controller, limit-switches and end-switches etc.) are connecting directly to crane interface on voltage level 220VAC, eventually 24VDC.
  • Thanks to crane card CRIO 2.0, which ensures complex logic of motor control, there is no need of any other auxiliary and blocking relays.
  • Possibility of application with original slip ring motorsu.
  • High safety of operation.
  • The right design of complete crane drive (gear - brake - motor - inverter) is the first step for safety function of crane drive.

Internal software of EMOTRON VXF 2.0 is designed for using of these inverters for hoisting applications without IRC sensors. The direct torque control of inverters, give the maximal starting torque with optimal magnetic flux of motor. Integrated current control, with low frequencies gives maximal load with zero speed of motor.

Special crane software gives the opportunity optimal control the brake. Internal safety circuit gives command „OK” to the brakes when it is assure, that the frequency inverter as well as the connected motor are without the failure. Brake is switch-off immediately when any trip comes from inverter or motor or from any other part of crane (acc. To ČSN standards).

Special applications

  • Non-tensional regulation: elimination of bridge crane seizing.
  • Grab crane control.
  • Synchronous operating of two cranes.
Grab control with frequency inverters

Examples of crane applications, see Reference list .

„Electronic flanges” for bridge and portal cranes

Using area of electronic flanges

ESK system - „Electronic flanges” was developed by Emotron and it is designed for bridge or portal cranes which have problems with seizing and excessive flanges wear of traveling wheels and rails. It happens mainly when there is a big crane span or low crane stiffness or in cases of unbalanced load of crane. Underestimate of this problems want to threaten the safety operation.

 

ESK system with frequency inverter prohibits the seizing of crane and extending the lifetime of crane wheels and rail and increasing the safety and reliability of crane. If this system is optimally designed, then the moving of crane is smoother, steady and without contact between wheel flange and rails.

How it works?

Electronic flanges system is made from three basic parts:
1. Measuring (distance sensors)
2. Regulation (PLC)
3. Speed control (frequency inverter)

There is continuously measuring of side distance between wheel and rail by the four distance sensors. The sensors are placed in each corner of crane for the most exact measured distance.
The regulation circuit (PLC) processing all four signals and determine the optimal axis of movement.
This principle looks very simple but there are any other terms which are important too. It is unequal crane bridge load, curved crane track, different friction torques on each wheel/gear, climatic influences (with outside cranes) etc.
Speed of right and left motor are controlled with frequency inverters by the output signals of regulator. It makes possible the independent speed control.

Technical realization

The measuring system wants to works with any type of sensor. But the best is to use ultrasonic sensor because it is able to work in the extreme operation conditions and it has very good characteristic.
The PLC with display and the keyboard is delivered with cabinet which is equipped by power supply, terminal board for connecting of all In/Out signals.
The keyboard and display are used for commissioning of the complete system. All signals and measured values are monitored and it is possible to arrange their simulation.
The movement drives are realized from standard asynchronous motors which are operated by frequency inverters EMOTRON VFX2.0.

 

Grab control with frequency inverters

 
   

Description

This electronic control is determined for four-grab dredger with two drives. It coordinates the cooperation of both drives. From the view of crane driver is the grab crane operated as normal hoisting application with Up/Down and Open/Close commands, thanks to this electronic control.

For grab operating are four basic commands necessary:

  • grab - up (mostly 4 steps)
  • grab - down (mostly 4 steps)
  • grab - open
  • grab - close

All these commands are entered directly by the joystick and it is possible to arbitrarily combine all this functions. When the grab is only partly open then it is possible to hoist or it directly in this status. Internal positioning regulation controlling that both (means bearing and closing) ropes will always in right ratio.

Manual grab operation

Bearing and closing drive are equipped by the switch of operation choice „Auto/Manual”. In normal operation are both set to „Auto”. When one of them or both are switched to „Manual” then electronic grab regulation is switched off immediately. Both drives can be operated separately but positioning regulation and synchronizing of drives is switched off.

Setting of grab positions

The first step during the commissioning is the setting the end-positions of grab (positions „open” and „close”) and save it to control regulator memory. It is possible to set it by the control panel „Power-Panel PP41”. After the end-positions was set-up, then is the grab ready to the test operation during which can be completely commissioned all drives.
This process should be repeated only when there were any mechanical changes on grab or after a long operation time.

Balancing the load moments of both lifting gear

Synchronous regulation of both drives provides that share of load torques of each drive during operation will equal. Optimal torque ratio of both drives is between 40% up to 60%. If the grab is fully open then torque of the closing drive must to be higher then torque of bearing drive.

Digging automationu

The grab must to know to take on the material. There is used the self weight of grab for take on the material. The bearer rope can't to lift the grab during this operation but it must to be continuously tensed. The ropes of both drives are heave in with the same differential torque. It is why the closing drive (when grab is closed) during hoisting must be operated with higher torque than bearing drive.

Automatic transition from closing to hoisting

For optimal time sequence of grab operation is required that hoisting of grab must start immediately after material take-on. When the grab-close command come at the same time as grab-hoist command then the grab start with hoisting immediately. But it is possible to set this commands for hoisting with not fully closed grab. Them the grab start with slow hoisting and after the fully closed grab it accelerate to maximal speed. It handles the minimal mechanical jerks during acceleration.

Display of trip status

The trip statuses could happen during operation of grab crane. It is signalized by actual flashing of two lights - „grab-open” and „grab-close”. The cause of trip you want to read on inverter display or on the power panel display.

Set-up parameters of grab control regulator

For setting of parameters is „Power Panel PP41” used. It contains from several lines display and keyboard. The display shows an actual data of both drives. The Set-Up menu is activated by pressing of F2 key and setting the password. All parameter are described in „help” messages.

Parameter setting is necessary only by the first commissioning and their corrections or changing's is recommended only during any operation changes, problems or trips.

CRANE Set 2.0

Crane card (option) - CRIO 2.0

This set is determined for frequency inverters Emotron VFX 2.0.

It is modification of previous crane optional CRIO card, with any differences and main of them is that the CRANE 2.0 is not equipped by PTC and ENCODER inputs. Inverter must be equipped by ENCODER 2.0 option and PTC/PT100 optional card for connection of IRC sensor or PTC sensor.

CRANE 2.0 card contains from special crane software and hardware and it was developed by the Emotron especially for crane drives applications with frequency inverters.

The communication and the complete controlling of the crane drive are made by CRIO card. It coordinates the co-operation of input commands with signals which are used for controlling of inverter (motor).

Instead of three basic speed control methods (4-speed controller, 3-position controller and analogue control) there are inputs for pre-limit and limit switches and two relay outputs which are used as no-trip and brake control.

The benefits of the CRANE option are: fast reversing, operation with two parameter sets, special braking modes etc.

Crane interface (option) - CI

CI option (Crane Interface) cooperates with CRIO2.0 (Emotron VFX2.0 inverters) or CRIO1.0 (Vectorflux VFB/VFX inverters).

CI is determined for galvanic separation of control voltage of the crane (mostly 230VAC) from the internal voltage of inverter (24VDC). By this is possible to work directly with standard crane control voltage 230VAC. This solution fully eliminates the possibility of signal interference and it is very important when the inverters are used.

CRIO interface

Encoder card (option) - ENCODER 2.0

This option is determined for frequency inverters Emotron VFX 2.0.

To the ENCODER 2.0 option you can set the IRC sensor with TTL or HTL logic with output A, A B, B, and A, B signals are shifted for 90 electrical degrees. The Enoder 2.0 contains the supply voltage output 24VDC or 5VDC.
The IRC sensors are mainly used with hoisting crane drives or drives which must to cooperate in synchronous mode, e.g. hoisting with two motors, grab cranes or synchronous mode of two bridge cranes.
It is possible to make the hoisting crane drive without the Encoder2.0 option but the minimal speed can't be lower than nominal speed of motor divide by 10.
If the required minimal speed is lower than 1/10 of nominal (means that minimal frequency 5Hz) then the IRC sensor is recommended. It is mainly the handling cranes when the accuracy of hoisting is very important (e.g. cranes which settling the load to the turning machine with high accuracy etc.).

Please contact your supplier when you are not sure if you need Encoder or not. It depends on many aspects.