Electrical motors for use in dry cargo equipment need to be powerful and fulfil high efficiency values to reduce energy consumption at the same time. Germany’s Franz Wo¨lfer Elektromaschinenfabrik Osnabru¨ck GmbH designs and produces special inverter-driven low-voltage squirrel-cage motors for cargo equipment such as conveyors and cranes, which meet both requirements.

A special rotor geometry leads to a higher pull-out torque of the motor. A Wo¨lfer motor has a pull-out torque of up to 400%, compared with a pull-out torque of approximately 250% with some other motors. This means that Wo¨lfer motors can handle higher overload requirements and the motor can provide high torque also in the high range of speed. In this way, the motor can also be controlled easily, even if it is operated at speeds of 1,600 or 1,800rpm.

Wo¨lfer’s goal is not only to optimize the efficiency of the motor itself, but to minimize the energy consumption and maximize the power of the whole equipment with the special motors. The special rotor-design additionally results in a lower inertia. Based on this, the total inertia of the power-train is reduced. This lower total inertia leads to lower energy consumption. On the other hand, it is possible to accelerate the power-train, using the same energy levels as another motor. Based on the faster acceleration and deceleration process, a higher number of goods can be handled. Therefore the user can increase turnover by handling a higher number of goods, or can reduce energy costs and thus protect by this the environment.

The lower inertia leads to further advantages; for example, other components can be downsized. Depending on the design of the equipment, smaller gearboxes, brakes, inverters or cable diameters can be used. Thereby the weight of the application is lower, reducing investment costs. Finally not only is the efficiency of the motor at a high level, the efficiency of the whole equipment is also increased by using Wo¨lfer motors.

Beside these technical characteristics the reliability of a motor is a critical factor. In motors which are driven by frequency-inverters, the windings need to resist partial discharges, so-called voltage peaks. By using material, which is designed for inverter operation, and handmade windings,Wo¨lfer achieves a very long lifetime of the windings. Also AC (alternating current) motors reduce the amount of maintenance required when compared with DC (direct current). While DC motors need periodic inspections and reconditioning, especially for brushes, AC motors get by with inspection of motor connections and lubrication. The AC motors run very smoothly, so that significant reductions in mechanical wear and mechanical repairs e. g. in cranes have been noticed. The higher reliability of the electric motors results in fewer outages due to motor failure.

“We apply our know-how to produce robust reliable motors for individually adapted drive mechanism solutions,” says Klaus Sprekelmeyer, Head of Sales at Wo¨lfer. “Our motors are built for use in extreme demanding environments, like dust, heat or marine conditions.” For 70 years now Franz Wo¨lfer Elektromaschinenfabrik has been developing and manufacturing electric motors for use in hoisting equipment, in and on ships as well as in general mechanical engineering.

Wo¨lfer provides steel-welded housings in addition to grey cast iron housing for surface-cooled motors, which is e. g. relevant to make a technology change as easy and efficient as possible. By the steel-welded design,Wo¨lfer provides 1:1 drop-in motors for retrofits. “Normally the new AC motor can be offered in a smaller frame size compared with the existing DC motor. Therefore the machinery house needs to be adjusted to the new dimensions. Wo¨lfer offers a new AC motor with minimized inertia, but with the same mounting dimensions as the DC motor. So the motor itself can be changed within one day, without modifying the basement of the machinery house and without shaft adjustments. This leads to a shorter downtime and lower cost,” says Sprekelmeyer. This steel-welded housing design is available for surface cooled applications like conveyor- and excavator motors.

Klaus Sprekelmeyer is the head of sales of Franz Wo¨lfer Elektromaschinenfabrik Osnabru¨ck GmbH. He has worked for the company for more than 16 years with over ten of these years in the sales department. In 1999, Sprekelmeyer started an apprenticeship for three years as a blue collar employee and white collar employee in parallel. After achieving several technical and commercial skill enhancements, Sprekelmeyer took over the responsibility for the sales department in 2007. Since the beginning of 2014, Sprekelmeyer has been a member of the board.