Annex B Safety Knowledge
57
(2) Pinhole in the insulator;
(3) Distance between parts is not enough;
(4) Insulation is crushed and broken:
The above cases can only be detected by ACW/DCW.
B.4 ACW/DCW
The ACW/DCW is adopted to test the ability to withstand of low-voltage electrical
equipment, insulation materials and the insulation structure. The basic theory for ACW/DCW
is to expose a product in a very harsh environment, if the product can maintain the normal
condition in this harsh environment, we can determine that in normal operating conditions,
the product will be able to maintain a normal condition.
Different products have different specifications. In general, during ACW/DCW, a
voltage higher than normal operating voltage is applied to the product for testing and holding
for a specified period. If within the stipulated time, the leakage current of a component is also
kept within the specified range, we can determine that the component should be safe under
normal operating conditions. Good design and insulating material will protect the user.
For ACW/DCW of general appliances, apply the stipulated voltage between the live
wire and the house. Measure the leakage current between them and compare it with the set
value, the conclusion of pass or not is obtained. The basic requirement is that, twice of the
operating voltage of the DUT plus 1000V is deemed as the test voltage standard. The test
voltage for some products may be higher than twice of the operating voltage plus +1000V.
For example, the operating voltage for some products is from 100V to 240V. The test voltage
for these products may be 1000V to 4000V or higher. Generally, the test voltage for products
with dual-insulation design may be higher than twice of the operating voltage plus +1000V.
B.4.1 Advantages/disadvantages of ACW/DCW
Please contact the safety test unit specified for the DUT what kind of voltage shall be
applied. Some products can accept both ACW and DCW, but there are some products which
only accept ACW or DCW. If the safety specification allows both ACW and DCW, the
manufacturer can decide which test is more appropriate. To achieve this purpose, the user
must understand the advantages and disadvantages of ACW/DCW.
B.4.2 Features and classification of ACW
Most devices for ACW/DCW will have some discrete electrical capacity. For ACW, this
discrete capacitor cannot be fully charged. There is a continuous current flow through these
discrete capacitors.
1 Advantages of ACW
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