Power Electronic Components for Materials Handling

This week, we will be discussing about various technological breakthroughs. First, we discussed about Mouser's MEMS on medical equipments. MEMS made the medical equipments, nowadays, more accurate and precise. CPRs, ultrasound machines, and other hospital equipments are vital in saving lives of all. In making those machines more accurate and precise, minimal to zero fatality will be met. Now, we will be discussing about new power electronic components for materials handling drive systems.

Power electronics may be small but these components help drive heavy machinery. Variety of drives can be found in lift trucks, and other materials handling equipment. They supply the mechanical energy to move the motors for hydraulic pump and propulsion, even used as auxiliary actuators for steering.

The majority of the electric drives under consideration makes use of AC or DC motors, additional types such as switched reluctance machines are presently gaining importance. Figures 2, 3, and 4 show schematics with a symbol of the respective machine, connected to an appropriate power section.

Power Semiconductor

Blocking voltage of the MOSFETs and possibly the diodes depends on battery voltage UZ in the intermediate circuit; there are several dominating levels: Automotive or truck like lead acid batteries are 12V or 24V versions, which is intended to be complemented by 42V in future. Besides, higher battery voltages up to some 100V are frequently used in industrial vehicles. The required rated blocking voltage is determined by the sum of battery voltage UZ and possible overvoltages. To minimise the latters within power section in switching operation, it is advantageous if phaseleg or chopper circuits are integrated in a single component with an internal low inductive current path. Besides, avalanche rated MOSFETs are able to dissipate some amount of energy, stored in the inevitable parasitic inductance of commutation path.

 

Semiconductors' required current ratings are determined by the power rating of the drive at nominal and overload. Each switch should be capable to conduct and control the required current at defined ambient conditions, the most important of which is temperature: In particular conduction and switching of the power semiconductor chips lead to power losses. The heat to dissipate is transferred from the component via the heatsink to ambient. This may not lead to a chip junction temperature exceeding the rating of the component. These considerations make trench MOSFETs a preferred choice for battery supplied industrial vehicles: This technology reduces the length of the current path in vertical power MOSFET chips and thus leads to a low on state resistance RDSon, while a sufficient switching speed for the typical frequencies of several kilohertz is maintained; it is particularly suitable for blocking voltages of up to some 100V...200V. In chopper circuits trench MOSFETs may advantageously be complemented by Schottky diodes with low forward voltage and fast switching capability. To optimize efficiency of the drive, which is an important feature of industrial vehicles influencing the operation time, it may be favorable to make a low on state resistance RDSon or high current rating respectively reduce conduction losses.

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http://www.eeweb.com/company-blog/ixys/power-electronic-components-for-materials-handling/