Resolvers are robust, reliable feedback systems for precise control of motor speeds. Speed controlled motors are required in almost all industries where electric machines are used for defined processes, e.g. mobile equipment ( caterpillars, cranes, diggers, trucks, etc.).

Detailed application description

Description of problem:

Dumper trucks transport minerals and waste in practically every mine anywhere in the world. Their profitability is based on the cost per ton transported. Following the initial purchase, running costs ultimately determine the economics of a dumper truck. Braking system maintenance plays a crucial role. Braking systems rely on friction: kinetic energy is converted into heat via brake discs. Wear is inevitable, leading to maintenance, expenditure for spare parts and downtime.

A major dumper truck producer approached LTN with an innovative idea: to reverse the principle of the drive train – from diesel engine via generator to wheel hub motors – and use the diesel engine to support the brakes. These motors power the motorised generator, which drives the fuel cut-off diesel engine via the motor shaft. The aim: maximum efficiency through a resolver in the generator control system.

Description of solution:

An application-specific resolver was developed in close cooperation with the customer. It needed to be adapted for the specific geometries of the generator, which had a shaft diameter much too large for a standard resolver. The environmental conditions (dust, water, hydraulic oils, vibration, etc.) in the context of mobile mining machinery also had to be considered.

A self-contained, enclosed resolver with IP68 protection was selected. The flange is hermetically sealed to the housing of the unit and thus protects the interior from fluids and dust. The bearing is sufficiently robust to withstand the permanent vibration of the diesel engine as well as smaller stones that are thrown up from the road.

With this solution, which was unveiled at MineExpo 2016 in Las Vegas, the operator achieves longer maintenance intervals for the braking system and hence considerable cost savings throughout the service life of the trucks.

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