CHARTS: Hysteresis & Eddy Current Loss -- SMCs Vs. Steel Lamination.

Posted by Horizon Technology - September 13, 2018

Have you ever wished you had superpowers that could stop both hysteresis and eddy current loss in a project that demanded high magnetic performance?

Core loss in magnetic material is a measure of the heat generated within the material as a result of the alternating current. High core losses equal a greatly inefficient magnetic part.

An inefficient magnetic part can bring down your whole design. So, how do you prevent it?

Eddy Current Loss & Hysteresis Loss

Total core loss is actually the combination of two types of loss:

  • Eddy loss: When changing frequencies, energy is consumed. Magnetic induction lags behind the magnetizing force
  • Hysteresis loss: When changing frequencies, energy is consumed

Both increase the heat level in the magnetic material. Heat = inefficiency. (We’ll give a much longer equation for you to use in a bit.)

Eddy current loss occurs in all A/C devices, including:

  • Motors
  • Transformers
  • Power supplies

Total Core Loss Chart

Let’s get more specific. Core losses in soft magnetic composite materials depend on the:

  • Material used
  • Component density
  • Heat treating

The following chart shows the total core loss of the three most commonly used soft magnetic composites (SMCs). It also compares them to traditional M47 and M19 steel lamination materials, both semi-processed to a 24 gauge (0.025” thick).

Core Loss Characteristics of Soft Magnetic Composites Vs. M47 & M19 Steel Laminations

core loss in induction motor(Measured at an induction level of 1.5 Tesla.)

The chart clearly shows that soft magnetic composites are best at higher frequencies. It’s also apparent that SMCs are superior to M47 laminate at frequencies above 400 Hz. On top of all that, the SMC 700 1P material is nearly equivalent to M19 steel lamination at about 1,000 Hz.

This core loss data assumes the SMCs were compacted to a density of 7.5 g/cm³. The data for the laminations was based on the core loss at 60 Hz for each of the two materials, then extrapolated using this equation:

Core losses SMC materials formula A

The core loss data for the SMC materials can be represented by the following equation:

Core losses SMC materials formulas-977438-edited
In the hands of your smartest engineer (maybe that’s you), this equation can
calculate your core losses at any level of:

  • Induction
  • Frequency
  • Part thickness

In other words, you can learn how much heat (aka total core loss) you’ll generate using a soft magnetic composite at densities below 7.5 g/cm³ under any specific condition. Remember that higher resistivity generates less heat.

This table gives the values for each of the three major SMC grades:

Values of Constants in the Equation Above

HORIZON blog Core losses SMC materials chart 2

What This Means to the Metal Components Buyer

The proof is in the numbers: Soft magnetic composites go where limited laminations cannot. As a designer or purchaser, it’s crucial you know the uses of soft magnetic composite compared with steel lamination:

  • Unique shape-making ability
  • Reduce number of parts per assembly
  • And the reduced losses we’ve talked about!

Soft magnetic composite materials are starting to outperform standard lamination materials at frequencies as low as 400. SMC even beat the popular, high-performing M19 lamination at lesser heat

SMC is attractive for new, modern, high frequency applications.

However, they are not historically ideal for induction motors used in fridges, air conditioners, etc.

That said, if you can reduce the operating cost of the product, you can spend more money on optimizing your motor. You’ll eventually save the extra money you put in on the front end.

Some pretty smart people are starting to use this concept. We hope you capitalize on the potential of soft magnetic composite, too.

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Topics: Powdered Metallurgy, Materials, Applications

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