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Table 38.1
Maximum acceptable surface temperatures
Table 38.1 effective April 13, 1993
Location Composition of surface
a
Metal Nonmetallic
°C °F °C °F
A handle or knob and other surfaces subject to
contact in operation and user maintenance
60 140 85 185
A surface subject to casual contact 70 158 95 203
Surfaces upon which a fixed or stationary
converter may be mounted in service
90 194 90 194
a
A handle, knob, or the like made of a material other than metal, that is plated or clad with metal having a thickness of 0.005
inch (0.13 mm) or less is considered a nonmetallic part.
39 Dielectric Voltage-Withstand Test
39.1 A converter or inverter, at the maximum operating temperature reached in normal use, shall
withstand for 1 minute without breakdown the application of a 60-hertz essentially sinusoidal potential of:
a) One thousand volts plus twice the maximum rated voltage:
1) Between the primary circuit and dead metal parts;
2) Between the primary and secondary circuits; and
3) Between all secondary windings, including any ferroresonant winding.
b) Five hundred volts between a secondary circuit operating at 50 volts or less and dead metal
parts; 1000 volts plus twice the maximum rated secondary circuit voltage between a secondary
circuit, including any ferroresonant winding, operating at more than 50 volts and dead metal
parts.
c) One thousand volts plus the rated voltage of a capacitor between the terminals of a
capacitor used across the line for radio-interference elimination or arc suppression.
39.1 effective April 13, 1993
39.1.1 A dc potential of 1.414 times the rms value of the ac potential specified in 39.1 may be used
instead of the ac potential.
39.1.1 added January 27, 1995
39.2 To determine whether a converter complies with the requirements in 39.1, the converter is to be
tested using a 500 volt-ampere or larger capacity transformer, the output voltage of which can be varied.
The applied potential is to be increased from zero to the required test value, and is to be held at that value
for 1 minute. The increase in applied potential is to be at a substantially uniform rate as rapid as is
consistent with correct indication of its value by a voltmeter.
OCTOBER 15, 2004 UL 458 57
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