Littelfuse Industrial Shock Block SB6100, Руководство пользователя

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SB6100 Industrial Shock Block
Page 13
Rev. 1-I-071520
FIGURE 13. SB6100 Temperature Derating Curve.
4. UL 943C Requirements
The following sections contain excerpts from the
UL 943C (1) Standard for Class C and D applications. For
EGFPD models, only Section 4.1 applies where selectable
trip levels from 6 to 100 mA are permitted
(20 mA is the only allowed trip level for GFCI devices in
NEC applications).
4.1 Trip Time
Class C and Class D GFCIs shall be capable of
interrupting the electric circuit to the load when the fault
current to ground ( I ) is within the range of a minimum of
20 mA through a maximum of (110% of the rated
voltage/500 Ω)
A
within the time interval (
T
) in
accordance with the relationship:
Where:
T is expressed in seconds, and
I is expressed in mA
Except that T is not required to be less than 20 ms.
The tripping threshold of these GFCIs shall be in the
range of 15 to 20 mA.
Fig. 14 shows the Class-A GFCI maximum-trip-time-
versus-current curve defined by UL 943 (with the above
formula); UL 943 also defines a limit to the formula, with
a minimum required trip time (or fastest trip speed) of
20 ms, which occurs at about 300 mA of ground-fault
current (I) per the formula. Class C and D GFCIs must
operate within this same curve, except that their operating
threshold is 15 to 20 mA (non-adjustable). See Fig. 15.
The SB6100 EFGPDs described in this manual also
operate within the Class-A formula, but have a 6- to
100-mA threshold setting range.
4.2 Grounding Circuit
The equipment grounding circuit of the circuit shall be
sufficiently low impedance that, should a fault to ground
occur, the voltage resulting across the grounding circuit
shall not exceed 150 V. The size of the grounding
conductor required for a circuit shall be determined by
calculating the resistance using the following formula and
converting that value to a wire gauge based on the length
of the equipment grounding conductor:
Where:
R
G
is the resistance of the equipment grounding
conductor
R
U
is the resistance of the ungrounded conductor, and
V
LG
is the RMS value of the supply line to ground
voltage
Refer to UL 943C Appendix A for a sample calculation
of grounding conductor size.