Sebastian Gruber

Zero sequence current elimination for dual-inverter fed machines with open-end windings

A dual-inverter allows to increase easily the maximum available power of a given inverter. When connecting two equal inverters to a machine with open end windings, the available power will raise by factor 3√. However, the dual inverter also introduces a new degree of freedom for the current, which is the zero component current. The dual inverter is known for developing zero component currents, which have three times the frequency of the fundamental current, and can be of a rather large amplitude. This paper analyses the origin of these zero component currents and shows an example of how to eliminate them. Moreover it shows the possibility to suppress zero component currents by using only software algorithms modifying the current control loop. There is no need for extra components. Moreover there are no drawbacks in the quality of control as well as regarding the maximum available voltage.

Reduction of detent force caused by the end effect of a high thrust tubular PMLSM using a genetic algorithm and FEM

In order to meet industrial safety standards in eccentric presses, the detent force of the acting high force tubular permanent magnet linear synchronous machines (PMLSM) should be reduced. The detent force is caused by two components: the slot effect and the end effect. Both effects are based on the reluctance change between permanent magnet (PM) and stator teeth. The slot effect is already optimized by the closing slot technique which is proven by measurements presented in this paper. The main topic is the reduction of detent force by using auxiliary poles at the end of the machine. Therefore a special genetic algorithm (GA) is developed which rates the simulation results of the FEM and produces new auxiliary poles. The combined simulation tries to find an optimal size and position for auxiliary poles to reduce the whole detent force. The numerical calculations propose a minimized detent force caused by the located poles, which is independent from the length of the machines (2, 3 or 5 modules).

Development and Test of a High Force Tubular Linear Drive Concept with Discrete Wound Coils for Industrial Applications

This paper deals with the development of a tubular permanent magnet linear drive with radial magnetized armature and discrete wound coils mounted on a star-shaped stator part. The rated force of the developed machine is 500 N per segment. This presented particular design results in a very economic product because all primary parts, except of the permanent magnets and coils, are made of standard non-laminated steel and are optimized for easy production and assembly. The control of this machine with a specially built low cost linear sensor based on the Hall-effect is also presented. The suitability of the design is proven by the demonstration of a prototype with measurements of thrust and cogging force.

System analysis and optimization of a pressure control for a hydraulic-Clutch-Brake-Combination actuated with a linear drive

This paper deals with the analysis of an electro-hydraulic system and conception of a pressure control. The controlled system consists of a permanetmagnet linear actuator, a hydraulic pressure line and a Clutch-Break-Combination (CBC). The linear actuator generates a force which causes the pressure in the hydraulic line. Depending on the system-pressure, the Clutch-Brake-Combination brakes or clutches with a different torque. Because of the integrated prestressed springs of the CBC, the controlled system is very nonlinear. In addition there are different disturbances, which makes it hardly controllable. The linear actuator is driven with a standard inverter.

Optimization of a high force tubular linear drive concept with discrete wound coils to fulfill safety standards in industrial applications

This paper deals with the next step of development of a tubular permanent magnet linear drive concept for industrial applications up to 3000N thrust force where low cogging forces are required to fulfill safety standards. The presented linear drive concept is designed for easy production and assembly of a few hundred units per year. It can be manufactured on standard production machines because all ferromagnetic parts are made of standard not-laminated steel. This results in a very economic product. Further more the drive concept includes an internal low cost position sensor based on the hall-effect. The different steps of development are proven by measurements of thrust and cogging forces of different prototypes.

Survey on energy efficiency measurements in heterogenous facility logistics systems

Basically there are two ways to improve the energy efficiency of heterogeneous material flow systems - modification of technical components and control with intelligent strategies. In order to reduce the consumed energy the design, configuration and control strategy of different conveyor systems have to be analyzed by mechanical and electrical measurements. To quantify the need of energy under conditions as close as possible to reality a testing facility with different conveyor elements and electrical drives with power monitoring capabilities was installed in order to give a database for further research activities. On the one hand the acquired data can be used to optimize the efficiency of the total drive train. On the other hand they conduce to develop new intelligent control strategies for an energy efficient operation of heterogeneous facility logistics system. Eventually, the design of a monitoring system in a testing facility is the topic of this contribution.

Controlling of medium voltage power-factor of photovoltaic power plants from the low voltage side

The effort to make the production of electrical energy much more environmental-friendly, large conventional power plants will be replaced by several smaller regenerative power plants. In order to improve stability and controllability, these smaller power plants are supposed to control the active power, the reactive power and the power factor in the medium voltage grid like conventional power plants. This paper will discuss three different methods to control the medium-voltage power factor from the low voltage side in consideration of parasitic effects from cables and transformers to fulfill the guidelines at the grid connection point. A method with a self-learning-algorithm will be implemented and proven by simulations and measurements on a test bench with inverter and 400 V to 10 kV grid transformer. The self-learning-algorithm will give the opportunity to reach every required power factor at the grid connection point.

Detent force reduction of a tubular linear drive by using a genetic algorithm and FEM - verification of simulation results

In order to meet industrial safety standards in eccentric presses, the detent force caused by the reluctance change between permanent magnet (PM) and stator teeth of the acting high force tubular permanent magnet linear synchronous machines (PMLSM) should be reduced. The detent force is generated by two components: the slot effect which is already decreased by the closing slot technique and proven in [3] and the end effect which will be optimized by using auxiliary poles at the end of the machine. Therefore a special genetic algorithm (GA) is developed which rates the simulation results of the FEM and produces new auxiliary poles. The combined simulation tries to find an optimal size and position for auxiliary poles to reduce the whole detent force. The numerical calculations propose a minimized detent force caused by the located poles, which is independent from the length of the machines (1 to 5 modules). The result will be proven by measurements.

Controlled input-output-shaft synchronisation by a linear drive actuated hydraulic clutch-brake-combination

The focus of this paper is the control to accelerate and decelerate a drive shaft exactly with a hydraulic clutch-brake-combination (CBC). The CBC is actuated by a permanent magnet linear synchronous machine (PMLSM) with an integrated hydraulic cylinder. The servo-converter-controlled-PMLSM is able to generate the pressure for the CBC. A superposed control cascade with a pressure control and a special synchronization control is implemented to vary the transmitted torque and therefore the accurate acceleration and deceleration of the drive shaft within a preset angle. This development ensures a controlled synchronization of the input-output shaft by a CBC in a specific point of time within a preset mechanical angle.

High force tubular linear actuator with integrated eddy current brake for spring-loaded systems

In order to meet safety standards in manufacturing industry many production machines are equipped with safety stop functions based on spring-loaded systems. This paper deals with an integrated eddy current brake of a high force tubular permanent magnet linear actuator for hydraulic applications with small actuating pathes. An analytical description of different design criteria for the integrated eddy current brake are shown. The special not rotational symmetrical design of the tubular linear actuator is transferred to a 2D transient FEM simulation model to predict the braking behavior caused by the spring load in case of an emergency stop. Measurements on a test bench are in good agreement with the simulation results and are used to validate the model.