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GV2, GV3, and GV7 Manual Motor Starters, Controllers, and Protectors
Specifications and Operating Curves
30
6/2010
GV7 Operating Curves
The current limiting capacity of the motor starter and protector is expressed by two curves that
illustrate the following, as a function of the prospective short-circuit current (the current that would flow
if no protection devices were installed):
• The actual peak current (limited)
• The thermal stress (in A
2
s), that is, the energy dissipated by the short-circuit in a conductor with a
resistance of 1 Ω
Example—The actual peak value of a 70 kA prospective short-circuit current limited by a
GV7RS220 is 20 kA. See page 32.
Example—For a GV7RS220, the peak value is limited to 20 kA for a prospective Isc of 40 kA.
Example—For a GV7RS220, and with a prospective Isc of 40 kA, an I
2
t of 7.5 x 10
5
A
2
s is
obtained, which requires the use of a PVC insulated copper cable with a wire size of 10 mm
2
(8 AWG).
Table 35:
Permissible Thermal Stresses for Cables (A
2
s)
S (mm
2
) 1.5 2.5 4 6 10 16 25 35 50
AWG 16 14 12 10 8 6 4 2 1
PVC
Insulation
Cu 2.97 x 10
4
8.26 x 10
4
2.12 x 10
5
4.76 x 10
5
1.32 x 10
6
3.4 x 10
6
8.26 x 10
6
1.62 x 10
7
3.31 x 10
7
Al——5.41 x 10
5
1.39 x 10
6
3.38 x 10
6
6.64 x 10
6
1.35 x 10
7
——
PRC
[1]
1
PRC = Cross-linked polyethylene
Cu 4.10 x 10
4
1.39 x 10
5
2.92 x 10
5
6.56 x 10
5
1.82 x 10
6
4.69 x 10
6
1.39 x 10
7
2.23 x 10
7
4.56 x 10
7
Al——7.52 x 10
5
1.93 x 10
6
4.70 x 10
6
9.23 x 10
6
1.88 x 10
7
——