LM1851 Unisonic Technologies, LM1851 Datasheet - Page 6

• Manufacturer Part Number: LM1851
• Description: Ground Fault Interrupter
• Manufacturer: Unisonic Technologies

UTC LM1851
due to normal fault only is as follows:
≤25 ms Specification
≤10 ms Maximum integration time that could be allowed
UTC
UL943 specifies ≤25 ms average trip time under these conditions. Calculation of C
-3 ms GFI turn-on time (15k and 1μF)
-8 ms Potential loss of one half-cycle due to fault current sense of half-cycles only
-4 ms Time required to open a sluggish circuit breaker
8 ms Value of integration time that accommodates component tolerances and other variables
Where T=integration time
therefore:
C
I =
×
C
C
t
=
V=threshold voltage
I=average fault current into C
t
t
= 0.01μF
=
heavy fault
current generated
(swamps I
1 × T
120V
current
division of
input sense
transformer
V
1000 turns
120
500
1 turn
R
AC(rms)
B
TH
×
UNISONIC TECHNOLOGIES CO., LTD.
)
1.6+0.4
0.4
LINE
×
×
Ct charging
on half-
cycles only
portion of
fault current
shunted
around GFI
R
1
2
×
G
t
R
+ R
N
S1
1000
NEUTRAL
×
1
17.5
N
rms to
average
conversion
HOT
0.91
×
LINEAR INTEGRATED CIRCUIT
1
2
×
GFI
R
1.6
0.91
G
(0.8) I
(0.2) I
HOT
NEUTRAL
× 0.0008
R
0.4
N
(7)
(6)
(5)
R
500
I
B
t
based upon charging currents
QW-R122-007,A
6