Electromagnetic flow meters are widely used for their ability to measure fluid flow without contact. However, they can sometimes experience electromagnetic losses, which can affect their performance. In this article, we will explore the three primary types of electromagnetic losses that can occur in flow meters and how to mitigate them.

1. Eddy Current Losses in the Metal Measuring Tube

Eddy current losses are a significant factor in the efficiency of electromagnetic flow meters. These losses increase with:

The length of the magnetic field's axial dimension.

The frequency of the excitation power source.

The strength of the magnetic field.

The diameter of the measuring tube.

The thickness of the tube walls.

The greater the eddy currents, the higher the eddy current losses, and the larger the phase difference between the magnetic induction intensity and the magnetic field current.

2. Hysteresis Losses

Hysteresis losses are caused by the hysteresis characteristics of magnetic materials. When the coil is powered by alternating current, the magnetic flux lags behind the current due to the magnetic material's hysteresis. If the magnetic induction intensity in the core has not reached saturation, the hysteresis loss is relatively small. To minimize this, electromagnetic flow meters use high permeability electrical steel sheets for the magnetic yoke and core. It is recommended that the rolling direction of the steel sheets aligns with the direction of the magnetic force lines to significantly reduce hysteresis losses.

3. Foucault Current Losses

Foucault current losses, also known as eddy current losses, occur in the magnetic yoke. To reduce these losses, the yoke should be made of materials with low electrical conductivity and high magnetic permeability. Insulating sheets should be used between each layer to further decrease losses. For typical power frequencies of several hertz, a steel sheet thickness of 0.25 to 0.5mm is usually sufficient to keep Foucault current losses within acceptable limits.

    Understanding the three types of electromagnetic losses in flow meters is crucial for maintaining their accuracy and efficiency. These losses are generally caused by interference around the flow meter, so it's essential to avoid installing flow meters in areas with potential interference. By addressing these issues during installation and choosing the right materials, you can ensure the optimal performance of your electromagnetic flow meters.