Electrical steel datasheets often list core loss values such as P1.5/50 or P1.7/50. These values describe loss under specific magnetic test conditions.

This guide explains how electrical steel core loss is reported, what P1.5/50 and P1.7/50 mean, and how to read these values when comparing datasheets.

Key Takeaways

P1.5/50 and P1.7/50 are specific total loss values reported in W/kg under defined magnetic test conditions.
The difference between them is the magnetic flux density used in the test: 1.5 T vs. 1.7 T, both at 50 Hz.

What Is an Electrical Steel Core Loss Test?

An electrical steel core loss test measures the power dissipated in the material when it is subjected to an alternating magnetic field.

The result is usually reported as specific total loss in watts per kilogram (W/kg) at a specified magnetic flux density and frequency.

Because core loss changes with both flux density and frequency, the W/kg value is meaningful only together with its test condition.

For example:

P1.5/50 ≤ 2.35 W/kg.

How Is Core Loss Written on an Electrical Steel Datasheet?

Electrical steel core loss can be reported at different combinations of magnetic flux density and frequency. Common examples include:

Test Designation	Meaning
P1.5/50	Specific total loss at 1.5 T and 50 Hz
P1.7/50	Specific total loss at 1.7 T and 50 Hz
P1.5/60	Specific total loss at 1.5 T and 60 Hz
P1.0/400	Specific total loss at 1.0 T and 400 Hz

What Does P1.5/50 Mean?

The notation P1.5/50 can be read in three parts.

P: Specific Total Loss

“P” refers to the specific total loss of the electrical steel under the stated test condition, normally expressed in W/kg.

When the test conditions are the same, a lower value means less power is dissipated per kilogram of material.

1.5: Magnetic Flux Density

The 1.5 indicates that the loss was measured at a magnetic flux density of 1.5 Tesla (T).

50: Frequency

The 50 indicates that the measurement was made at 50 Hz.

What Does P1.7/50 Mean?

P1.7/50 follows the same notation and represents specific total loss measured at 1.7 T and 50 Hz.

Compared with P1.5/50, the frequency is unchanged, while the magnetic flux density increases from 1.5 T to 1.7 T.

P1.5/50 vs P1.7/50: What Is the Difference?

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P1.5/50 vs P1.7/50 electrical steel core loss comparison at 1.5 T and 1.7 T, both at 50 Hz

P1.5/50 and P1.7/50 are measured at the same frequency but at different magnetic flux densities.

Item	P1.5/50	P1.7/50
Magnetic flux density	1.5 T	1.7 T
Frequency	50 Hz	50 Hz
Typical unit	W/kg	W/kg
Same test point?	No	No
Directly comparable by W/kg alone?	No	No

For example:

Material A: P1.5/50 = 1.10 W/kg
Material B: P1.7/50 = 1.25 W/kg

Material A cannot be judged as having lower core loss than Material B from these two values alone because the measurements were made at different flux densities.

Why Does Magnetic Flux Density Change Core Loss?

Core loss changes with magnetic flux density. As flux density increases, the material undergoes stronger magnetic excitation, and the hysteresis and eddy-current-related components of total loss also change.

The same electrical steel can therefore show different W/kg values at 1.5 T and 1.7 T.

Why Frequency Must Also Match

Core loss also changes with frequency.

For example, P1.5/50 and P1.5/60 are both measured at 1.5 T, but at 50 Hz and 60 Hz respectively. The values therefore represent different test conditions.

A conventional 50 Hz core loss value may not provide enough information to evaluate high-frequency performance, where loss behavior can change significantly as frequency increases.

Can P1.5/50 Be Converted to P1.7/50?

There is no universal conversion factor between P1.5/50 and P1.7/50. The relationship depends on the material's magnetic characteristics, grade, thickness, grain orientation, and processing condition.

If a project requires a P1.7/50 value, use a measured or specified P1.7/50 value rather than estimating it from P1.5/50 with a fixed percentage.

How to Compare Core Loss Values Between Two Datasheets

Before comparing two W/kg values, check whether the underlying test conditions are comparable.

1. Check the Magnetic Flux Density

Compare values measured at the same magnetic flux density.

2. Check the Frequency

Compare values measured at the same frequency.

3. Check the Thickness

Material thickness can affect magnetic loss, especially the eddy-current component.

A 0.27 mm material and a 0.50 mm material should therefore not be evaluated from the W/kg value alone.

4. Check the Material Type

GOES and NGOES are designed for different magnetic applications and should not be compared simply because both datasheets contain core loss values.

5. Check the Test Method or Standard

The reported value should also be reviewed together with the applicable test method or material standard.

HWHG’s electrical steel inspection process includes magnetic performance checks on finished coils before shipment, with core loss verified where required alongside dimensional, surface, and coating inspections. This provides a closer link between the stated datasheet value and the actual batch supplied.

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HWHG electrical steel quality inspection including core loss, dimensional, surface, and coating checks

Example: How to Read a Core Loss Specification

Consider the following specification:

P1.5/50 ≤ 2.35 W/kg

It can be read as:

P
Specific total loss.

1.5
Measured at a magnetic flux density of 1.5 T.

50
Measured at a frequency of 50 Hz.

≤ 2.35 W/kg
The specified maximum specific total loss under that test condition.

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How to read P1.5/50 ≤ 2.35 W/kg on an electrical steel datasheet

Which Core Loss Test Point Matters for Your Application?

The relevant test point depends on the material and application.

For transformer-oriented electrical steel, core loss at power frequency and relatively high magnetic induction is an important parameter. P1.7/50 is therefore commonly encountered in GOES specifications.

For non-grain-oriented electrical steel used in motors and generators, P1.5/50 or P1.5/60 may appear in conventional datasheets.

For high-speed or high-frequency motor applications, however, a single 50 Hz loss value may not be sufficient. Engineers may also need loss data at higher frequencies and different magnetic flux densities.

What Core Loss Information Should Be Included in an RFQ?

If core loss is part of the material requirement, include the test condition together with the target value rather than specifying only “low-loss electrical steel.”

Useful information can include:

electrical steel type
grade
thickness
required core loss value
magnetic flux density
frequency
applicable standard
coil dimensions
application

For example:

NGOES, 0.35 mm, P1.5/50 ≤ 2.35 W/kg, for motor laminations.

Conclusion

P1.5/50 and P1.7/50 are core loss test designations, not electrical steel grades. They report specific total loss at different magnetic flux densities: 1.5 T and 1.7 T respectively, both at 50 Hz.

For datasheet comparison, use W/kg values only after confirming that the relevant test conditions are comparable.

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