UL 1449:2005 pdf download – Transient Voltage Surge Suppressors.
30.3 When the use of cheesecloth is specified, the cloth to be used is to be bleached cheesecloth running
14 – 15 yd2lb (approximately 26 – 28 m2/kg) and having what is known as a count of 32 by 28, that is, for any square inch, 32 threads in one direction and 28 threads in the other direction (for any square centimeter, 13 threads by 11 threads).
30.4 A TVSS with a maximum continuous operating voltage (MCOV) greater than the rated system
operating voltage shall be tested and comply with all performance requirements at the MCOV.
30.4 added June 6, 2001
31 Leakage Current Test
31.1 When tested in accordance with 31.3 – 31.8, the leakage current of cord-connected or direct-plug-in TVSS shall not be more than 0.5 mA.
Exception No. 1: Cord connected or direct plug-in TVSS marked in accordance with 61.6 shall not have leakage current more than 3.5 mA.
Exception No. 2: For TVSS intended to be employed between line and ground as a component of a
cord-connected product, the leakage current shall be measured through the TVSS.
31.1 efective February 16, 1998
31.2 Leakage current refers to all currents, including capacitively coupled currents, that may be conveyed between exposed surfaces of a TVSS and ground or other exposed surfaces of a TVSS.
31.2 efecive February 16, 1998
31.2.1 A TVSS provided with solid-state electronic circuit that operates and is relied upon for safe operation of the device during this test shall be tested as follows during the test:
a) With the circuit functioning as intended;
b) With the circuit open-circuited; and
c) With the circuit short-circuited.
Exception: A solid-state electronic circuit that has been investigated and found to comply with the requirements of the Standard for Tests for Safety-Related Controls Employing Solid-State Devices, UL 991, is not required to be tested as described in (a)- (C).
Added 312.1 ffective December 7. 2000
31.3 All exposed surfaces and the receptacle grounding contact, if provided, are to be tested for leakage current. The leakage currents from these surfaces, and a grounding contact, are to be measured to the grounded supply conductor individually as well as collectively if simultaneously accessible, and from one surface to another if simultaneously accessible. Parts are to be considered exposed surfaces unless guarded by an enclosure considered acceptable for protection against electric shock as defined in Accessiblity of Live Parts, Section 13. Surfaces are to be considered simultaneously accessible if they can be readily contacted by one or both hands of a person at the same time.
31.4 If a surface other than metal is used for the enclosure or part of the enclosure, the leakage current is to be measured using metal foil having an area of 10 x 20 cm (4 x 8 inches) in contact with the surface.
If the surface is less than 10 x 20 cm (4 x 8 inches), the metal foil is to be the same size as the surface.
The metal foil is not to remain in place long enough to affect the temperature of the TVSS.
31.4 efeclive February 16, 1998
31.5 The measurement circuit for leakage current is to be as shown in Figure 31.2 for three-phase TVSS.
The measurement instrument is defined in (a) – (d) of this paragraph. The meter that is actually used for a measurement need only indicate the same numerical value for a particular measurement as would the defined instrument. The meter used need not have all the attributes of the defined instrument.
a) The meter is to have an input impedance of 1500 ohms resistve shunted by a capacitance
of 0.15 μF.
b) The meter is to indicate 1.11 times the average of the ull-wave rectifed composite
waveform of the voltage across the resistor or current through the resistor.
c) Over a frequency range of 0 – 100 kHz, the measurement circuitry is to have a frequency
response – ration of indicated to actual value of current – that is equal to the ratio of the
impedance of a 1500 ohm resistor shunted by a 0.15 μF capacitor to 1500 ohms. At an
indication of 0.5 mA and 5 mA, the measurement is to have an error of not more than 5
d) Unless the meter is used to measure leakage from one part of a TVSS to another, the meter
is to be connected between accessible parts and the grounded supply conductor.