KMP_786C_C03 Page 6 of 7

786 Series

General Purpose Pulse Transformers

www.murata.com

TUBE OUTLINE DIMENSIONS

0.60±0.15

(0.023±0.005)

4.00 (0.16)

5.50 (0.22)

10.95

(0.43)

12.95

(0.51)

3.80

(0.15)

15.70 (0.62)

Tube length: 465±2 (18.3±0.08). Tube quantity: 50.

Tube material: Antistatic coated clear pvc.

Unless otherwise stated all dimensions in mm (inches) ±0.25 (0.01).

TECHNICAL NOTES

ISOLATION

VOLTAGE

‘Hi Pot Test’, ‘Flash Tested’, ‘Withstand Volt-

age’, ‘Proof Voltage’, ‘Dielectric Withstand

Voltage’ & ‘Isolation Test Voltage’ are all terms

that relate to the same thing, a test voltage,

applied for a specified time, across a compo-

nent designed to provide electrical isolation, to

verify the integrity of that isolation.

All products in this series are 100% production

tested at their stated isolation voltage.

A question commonly asked is, “What is the

continuous voltage that can be applied across

the part in normal operation?”

For a part holding no specific agency approv-

als both input and output should normally be

maintained within SELV limits i.e. less than

42.4V peak, or 60VDC. The isolation test

voltage represents a measure of immunity to

transient voltages and the part should never

be used as an element of a safety isolation

system. The part could be expected to function

correctly with several hundred volts offset

applied continuously across the isolation bar-

rier; but then the circuitry on both sides of the

barrier must be regarded as operating at an

unsafe voltage and further isolation/insulation

systems must form a barrier between these

circuits and any user-accessible circuitry ac-

cording to safety standard requirements.

REPEATED HIGH-VOLTAGE

ISOLATION TESTING

It is well known that repeated high-voltage

isolation testing of a barrier component can

actually degrade isolation capability, to a

lesser or greater degree depending on ma-

terials, construction and environment. This

series has toroidal isolation transformers,

with no additional insulation between pri-

mary and secondary windings of enamelled

wire. While parts can be expected to with-

stand several times the stated test voltage,

the isolation capability does depend on the

wire insulation. Any material, including this

enamel (typically polyurethane) is suscep-

tible to eventual chemical degradation when

subject to very high applied voltages thus

implying that the number of tests should be

strictly limited. We therefore strongly advise

against repeated high voltage isolation test-

ing, but if it is absolutely required, that the

voltage be reduced by 20% from specified

test voltage.

This consideration equally applies to agency

recognised parts rated for better than

functional isolation where the wire enamel

insulation is always supplemented by a

further insulation system of physical spacing

or barriers.