Annex B Safety Knowledge
62
leakage and Line leakage are common test terms. In fact, it can be divided into three types of
tests: Earth Leakage Current, Enclosure Leakage Current and Applied Part Leakage. The
main difference is that the measurement locations of the test rod (clamp) are different. Earth
Leakage Current means the leakage current flowing back to the earth through the earth line.
Enclosure Leakage Current means the leakage current flowing back to the earth through the
body as any one touches the enclosure. Applied Part Leakage or Patient Lead Leakage means
the leakage current flowing between or to applied parts. This test is only required for medical
instruments in general. The main purpose of these tests is to keep users safe during operating
or holding of parts, and avoid risk of electric shock.
LC is a type of test for the leakage current of a product flowing through a set of
simulated body impedance circuit as a measurement base. The simulated body impedance
circuit is called Measuring Device (MD). For the impedance of human body, the location,
size and current flow of man-machine contact points are different, so the specifications of
MD depends on the types of tests and the allowed maximum leakage current. Measuring of
leakage current is required for not only the normal operation of product and a fault, and shall
be conducted after exchanging of polarity of power supply, to avoid any problems and
dangers caused by improper use or faults when the product works under the highest input
voltage (typically 110% or 106% of input voltage rating).
LC is usually required for product development and design and verification, to confirm
that this product can meet the design specifications of the standard. However, this cannot
guarantee that each product in the production line can meet the specification requirements, so
this test is required for each product in the production line, in order to guarantee the products
comply with specifications.
B.7.1 Type of LC
Include static LC and dynamic LC.
1. Static LC
The Static LC includes two steps. The first step is as shown in Figure B-7-1. The second
step is as shown in Figure B-7-2.
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