The service life of electro motors is usually equated with the service life of the bearings and for electro motors is around 20.000 hours. But what factors actually influence the service life of motors? Here are the three most important ones:
Temperature:
The problem: high temperatures in the motor damage the lubricants. The lubricants lose their effectiveness => the bearing overheats
Solutions: Baumüller uses high temperature greases that allow high temperatures and thus high rotation speeds.
Bearing currents:
The problem: In motor-converter combinations, bearing currents can develop in some cases. The voltage, instead of grounding through the converter, takes the path of least resistance through the shaft of the motor and the bearings and is discharged towards the ground. This results in vibrations => the bearing overheats and wears prematurely
Solutions: use of common mode chokes and/or current-insulated bearings
Vibration, oscillation, impacts:
The problem: Vibration, oscillation or impacts that impact the motor affect different parts of the drive and can damage different parts of the motor => the service life is shortened, the process quality suffers
Here, too, solutions exist: Vibration measurements and drive simulations offer a remedy. If the stressloads are known, numerous adjusting screws are rotated, which increase the shock resistance of electro motors.
Effects of vibration, oscillation and shock loads
Whether it is oscillation, vibration or shock load, the effects that result are difficult to predict. Different problems lead to the failure of the motor or to process errors. Damage to the bearing or the windings play the main role here, but there can be other problems:
- Bearing damage: Bearing races develop cracks, rolling bodies are damaged
- Windings: Insulation is rubbed off, short circuits result
- structural damage to the housing
- Crack on the bearing shield
- Damage to the screw connections from the flange to the machine
- Sensor problems: the impact can cause the sensor to lose contact, resulting in signal interruption
When damage occurs, these problems can incur substantial costs and significant losses of time in the market launch of new machines. A better option is to avoid such damage from the beginning. Here drive simulations are helpful in anticipating strong oscillations and any resulting damage right from the project planning phase. Therefore Baumüller carries out drive simulations at an early point in the development phase. The drive expert can then head off problems with structural modifications or modified controller settings. This is possible because of a multi-version motor portfolio with numerous special options and extensive experience in electrical drive technology.
Solution options: Adjusting screws for greater shock resistance
The measurements and simulations then provide the basis for the solution. As a drive manufacturer, Baumüller draws on a broad reservoir of experience and can develop a range of proposals for problem resolution. Example include:
- Adaptations in controlling: Rounding the cycle
- Installing absorbers
- Decoupling the motor (e.g. belt)
- Designing motor more robustly
A few adjusting screws on the motor can be rotated to avoid the effects of vibrations or shocks. Different bearing options, such as deep groove ball bearings, are included as options in the standard portfolio. At Baumüller, with its extensive expertise as a motor manufacturer, a range of other adaptations to the motor are also possible, e.g. reinforced bearing shields or cushioned motor bases.
Industries that have traditionally produced mechanical loads on the motor are well known and already have solutions in the Baumüller portfolio. The high-torque motors DST2, for example, which are available with the integrated thrust bearing. The version with thrust bearing was specially developed for use in extrusion technology: The integrated thrust bearing absorbs the axial forces that act on the motor, which arise from the counter-pressure in the process section. The motor is thus specially designed for these loads and no losses in service life are likely.
Teamwork: Efficient
Teamwork pays off. Early cooperation between machine builder and drive manufacturer is recommended for applications where problems commonly arise from process-related shocks or vibrations. This way faults can be calculated beforehand and avoided, thus saving time and costs. Simulation technologies allow for loads to be represented so realistically that proposals can be made on this basis for extending the service life. The modeling of electro motors has become established as an alternative to prototype building, thus saving additional resources. In addition, a spatial independence emerges, which is more and more in demand, thus simplifying collaboration. Simulations also help with error analysis in the event of an incident. The areas of vibration measurement, vibration simulation and drive simulation are part of the Baumüller service spectrum.
