**5. Case study 1: Derrick crane**

The experimental behavior analysis of some drives is considered in a derrick crane, which serves for load handling in many industry branches. The main task in adjustable speed drives design is a safe, multi-axis movement that allows material handling throughout the working area. The derrick crane with following technical details has been taken for experimentation with adjustable frequency drive:


Electrical Drives for Crane Application 147

Power flows from the line through the input transformer and the input reactance into AFE, creating a common DC bus. The inverters take energy from the common DC bus to control

Fig.15a) shows a hoist movement with the 30% of full load and Fig.15b) for auxiliary hoist with an unloaded hook measured in similar conditions. In Fig.15a), curve 1 gives the actual speed signal (reference speed signal is given at 100% from the crane driver joystick command). Curves 2, 3 and 4 show the torque, power and motor current, respectively. After an acceleration period (ending at 5 s), a constant torque is delivered. This transition in torque level coincides with reaching the prescribed speed. At 17.5 s, the speed reference signal is made zero (stop command). The driving torque becomes zero and the system decelerates due to gravity. After 20 s, zero speed is reached, and the drive has to deliver the torque required for holding the load before closing the mechanical brake. After that the same the same measurements were performed during lowering. Due to high friction losses, torque was required to start the decent. After short initial period, only the dynamic friction is present, yielding a small driving torque. After the acceleration, the power flow is reversed and the drive lowers the load at a constant speed. From 43 s on, the system is braked with

The same measurements were performed during lowering and hoist movement with the 30% of full load, Fig. 16a). The reference speed was 25, 50, 75 and 100% of rated speed. As on the Fig.15 actual speed, motor torque, power and current are shown. After that for jib-boom motion the same signal was record as shown on Fig.16b). In both figure regenerative periods

From the Fig.15 and Fog.16, can be seen periods when the energy recovery occurs at the point of load lowering. It is very important to point out that the AFE topology allows for

fully regenerative operation, which is quite important for crane application.

Line Filter Module (EMC filter, line contactor and charging circuit).

the induction motors for the different movements.

Fig. 14. Single line power circuit topology.

maximum torque, until standstill.

during the lowering, at any reference speed, can be seen.

Active Infeed Converter.

Line Filter Choke


Using AFE rectifier/regenerative unit on common DC bus, six groups of inverter-motor combinations are supplied:


The rating of the AFE rectifier/regenerative unit output at cos=1 and 400 V supply voltage is 177 kW. This is far less than the sum of the ratings of the individual invertors, being 300 kW. In the Fig.13 crane with indicated drives is shown.

Fig. 13. Derrick crane with indicated drives.

Fig. 14 shows the power circuit topology of the derrick crane using AFEs at the input side. The AFE is connected upstream to the standard frequency inverter and consists of three components:


Using AFE rectifier/regenerative unit on common DC bus, six groups of inverter-motor

The rating of the AFE rectifier/regenerative unit output at cos=1 and 400 V supply voltage is 177 kW. This is far less than the sum of the ratings of the individual invertors, being

Fig. 14 shows the power circuit topology of the derrick crane using AFEs at the input side. The AFE is connected upstream to the standard frequency inverter and consists of three




300 kW. In the Fig.13 crane with indicated drives is shown.

Fig. 13. Derrick crane with indicated drives.

components:

Jib boom radius: 0-82.5;

combinations are supplied:

kW motor,

 Length of runway rail path: 350 m Working conditions: outdoor.

> Power flows from the line through the input transformer and the input reactance into AFE, creating a common DC bus. The inverters take energy from the common DC bus to control the induction motors for the different movements.

Fig. 14. Single line power circuit topology.

Fig.15a) shows a hoist movement with the 30% of full load and Fig.15b) for auxiliary hoist with an unloaded hook measured in similar conditions. In Fig.15a), curve 1 gives the actual speed signal (reference speed signal is given at 100% from the crane driver joystick command). Curves 2, 3 and 4 show the torque, power and motor current, respectively. After an acceleration period (ending at 5 s), a constant torque is delivered. This transition in torque level coincides with reaching the prescribed speed. At 17.5 s, the speed reference signal is made zero (stop command). The driving torque becomes zero and the system decelerates due to gravity. After 20 s, zero speed is reached, and the drive has to deliver the torque required for holding the load before closing the mechanical brake. After that the same the same measurements were performed during lowering. Due to high friction losses, torque was required to start the decent. After short initial period, only the dynamic friction is present, yielding a small driving torque. After the acceleration, the power flow is reversed and the drive lowers the load at a constant speed. From 43 s on, the system is braked with maximum torque, until standstill.

The same measurements were performed during lowering and hoist movement with the 30% of full load, Fig. 16a). The reference speed was 25, 50, 75 and 100% of rated speed. As on the Fig.15 actual speed, motor torque, power and current are shown. After that for jib-boom motion the same signal was record as shown on Fig.16b). In both figure regenerative periods during the lowering, at any reference speed, can be seen.

From the Fig.15 and Fog.16, can be seen periods when the energy recovery occurs at the point of load lowering. It is very important to point out that the AFE topology allows for fully regenerative operation, which is quite important for crane application.

Electrical Drives for Crane Application 149

Different tests have been performed on the system to show some of the capabilities in the AFE inverter system. The measurements are done at steady-state operation. During experiments, the DC link voltage is boosted to 650 V. The first test is rectifier system operation when the induction machine operates as motor during lifting of the load, Fig.17a), and second test is regenerative operation during lowering of the load, Fig.17.b). Both figures show the measured line currents, line voltages and DC voltage. It can be observed a high stationary performance both in motor and generator operation. The line current is nearly a

Fig. 17. Waveforms under steady-state operation: Line voltage, line current and dc link

The experimental behavior analysis of some drives is considered on the example of crane with wide span, which in sugar factory serves for continuous transport of sugar beet from

The crane with following details has been taken for experimentation with adjustable

Gantry crane for sugar beet storage is designed from the following functional parts: 1. Gantry drive (16 m/min) with four induction motors of 5.5 kW, two per leg.

2. System conveyor belts (2 m/s) with "battered" (30kW), horizontal (30kW) and

6. Decentralized crane control system with appropriate PLC, Profibus communication between converters and other intelligent devices (encoders, operator panels etc.).

sine wave with unity power factor while DC voltage is unchanged.

voltage a) motor operation, b) generator operation.

**6. Case study 2: Wide span gantry crane** 

the reception position to the factory storage.

 Handling capacity: 500 t/h; Gantry span: 64.5 m; Runway rail path: 300 m; Hoist height: 18 m;

Working conditions: outdoor.

"butterfly" conveyor (11kW).

5. Motor driven cable reel (1.1 kW).

4. "Butterfly" hoist (3 kW).

3. Trolley drive (12 m/min) with four motors of 1.1kW.

frequency drive:

Fig. 15. Measured pattern of the a) hoist motion, b) auxiliary hoist.

Fig. 16. Measured pattern at 25, 50, 75 and 100% of rated speed a) hoist motion, b) jib motion.

 

> 

**-40**

**-20**

 **-100 -50 0 50 100**

Power [%]

MotorTorque [%]

Speed [%]

Current [%]

Fig. 16. Measured pattern at 25, 50, 75 and 100% of rated speed a) hoist motion, b) jib

 

 

 

**-40**

**-40**

 **-100 -50 0 50 100**

Speed [%]

MotorTorque [%]

Power [%]

Current [%]

**0 10 20 30 40**

Time [s]

**0 10 20 30 40 50**

Time [s]

 

 

 

 

> 

**-40**

**-20**

**-100**

Speed [%]

Power [%]

Torque [%]

Current [%]

motion.

 

 

 

**-40**

**-20**

 **-100 -50 0 50 100**

Speed [%]

Power [%]

MotorTorque [%]

Current [%]

**0 10 20 30 40 50**

Time [s]

**0 10 20 30 40 50**

Time [s]

Fig. 15. Measured pattern of the a) hoist motion, b) auxiliary hoist.

 

 

 

Different tests have been performed on the system to show some of the capabilities in the AFE inverter system. The measurements are done at steady-state operation. During experiments, the DC link voltage is boosted to 650 V. The first test is rectifier system operation when the induction machine operates as motor during lifting of the load, Fig.17a), and second test is regenerative operation during lowering of the load, Fig.17.b). Both figures show the measured line currents, line voltages and DC voltage. It can be observed a high stationary performance both in motor and generator operation. The line current is nearly a sine wave with unity power factor while DC voltage is unchanged.

Fig. 17. Waveforms under steady-state operation: Line voltage, line current and dc link voltage a) motor operation, b) generator operation.
