2

© KEMET Electronics Corporation • KEMET Tower • One East Broward Boulevard

E5010_ESD-R-SR • 9/12/2018

Fort Lauderdale, FL 33301 USA • 954-766-2800 • www.kemet.com

EMI Core – ESD-R-SR Toroidal Cores for Round Cables for Low Frequency at 150 kHz (Bare, coated & with case)

Turns and Impedance Characteristics

When the desired performance of an EMI core cannot be

obtained with a single pass through the core, the impedance

characteristics can be changed with multiple turns.

A turn is counted by the number of lead-wire windings which pass

through the inner hole of the core. Windings on the outside of the

core do not count.

See Figure 1 for examples of one, two, and three turns.

Adding turns will result in higher impedance while also lowering

the effective frequency range.

See Figure 2 for an example.

Core Material and Effective Frequency Range

There are two ferrite material options for KEMET

EMI Cores: Nickel Zinc (Ni-Zn) and Manganese

Zinc (Mn-Zn). Each core material has a different

resistance and effective frequency range. The

MnZn core material has a lower resistance

compared to the Ni-Zn; therefore, adequate

insulation is required before use.

The Ni-Zn core material is typically effective

for frequencies in the MHz band range such as

the FM-band, while the Mn-Zn core material is

typically effective for the kHz band range such as

the AM-band. See Figure 3.

It is recommended to measure the actual

frequency range effectiveness in the target

application.

3T

2T

1T

Figure 1 – How to count turns

Resonance point changes to lower band

3T

2T

1T

Frequency (MHz)

10,000

1

10

100

1,000

1,000

100

10

1

Figure 2 – Relationship between impedance and turn count.

(Representative example: ESD-R-16C)

Frequency (MHz)

AM band range

FM band range

Mn-Zn series core

Ni-Zn series core

1,000

100

10

1

0.01

0.1

1

10

100

1,000

Figure 3 – Effective band range of Mn-Zn and Ni-Zn ferrite core material.

(Representative example, measured with same-dimension ring core)