GE Industrial Solutions ASTAT-XT RVSS PANEL - Manual (Page 17)

DEH40622 - Page 9 AN BL-0350, Rev.01, 08/20/2010
ASTAT-XT RVSS PANEL
4. Adjustments
The Solid State RVSS panel has several user settable adjustments, which allow it to be tailored specifically
for your 3-phase induction motor. Setting these adjustments appropriately is an important factor in
ensuring that applicable safety codes are met and that your panel, wiring, and motor are adequately
protected. The following list comprises all of the user adjustable devices/components inside the Solid
State RVSS panel. The user may wish to have a copy of NFPA 70-2008 (commonly known as the
National Electric Code or simply NEC) available for reference when setting these adjustments.
Input Fuses
In general there are two configurations that utilize input fuses; 1) input
disconnect with load side separately mounted fuses and 2) input Fused
Disconnect where the fuses are an integral part of the disconnect. If
your panel was ordered with the circuit breaker option, the disconnect
device and fuses are replaced by the circuit breaker. For Fused Disconnect
panels, the main input fuses provided with your panel has been closely
coordinated to provide short circuit protection for the starter along with
short circuit and over current protection for the motor. In “Soft Starter”
mode of operation, the fuses only provide short circuit protection due to
the fact that the starter has inherent over current protection. In “BYPASS”
mode of operation, the fuses provide both short circuit and over current
protection for the motor.
UL listed Class J time-delay fuses are provided with your Disconnect
panel. These fuses have been sized in accordance to NEC section 450-52
and Table 450-152. NEC states fuses of this type are to be sized at
175% of motor full-load amps (FLA). Due to the fact that actual motor
FLA along with starting current requirements vary between manufacturer
and motor types, the fuses provided are based on standard NEC motor
data. Verify that the input fuse amp rating is less than or equal to the
actual motor FLA * 1.75. In the case where the actual motor FLA * 1.75
is less than the provided fuses amp rating then smaller fuses may need
to be installed to be in compliance with NEC section 430-52 and Table
430-152. Please note exception 1 to NEC 430-52, which states that where
the calculated fuse amp rating does not correspond to a standard fuse
size the next higher standard fuse size may be used. In cases where the
fuses provided is not sufficient for the starting current requirements of the
motor, please note exception 2-b to NEC 430-52. Exception 2-b states the
rating of a time-delay fuse may be increased but shall not exceed 225%
of the motor FLA in any case. In the case where a larger or smaller
fuse is required, a limiting factor in the panel may be the fuse holder.
The appendices provide a table for the maximum fuses size permitted in
the existing fuse holder.
Coordinating the fuses for the Solid State RVSS panel is the over current
protection coordination between the Class 20/30 overload relay and the
fuse’s over current protection. This coordination is to avoid nuisance
blowing of fuses. Coordination between the Softstarter short circuit rating
and the fuse’s RMS let through currents during a short circuit condition
has also been closely evaluated. Changing the main input fuses may
impact one or both of the above coordination issues. Therefore if it is
necessary to change the input fuses, please consult your preferred fuse
supplier and/or your local GE starter distributor for Type 2 and overload
relay coordination.
Circuit Breaker Trip Level The optional circuit breaker in the Solid State RVSS is a solid state Spectra
RMS
TM
molded case circuit breaker from GE. The purpose of the circuit
breaker is to provide short circuit protection and over current for the panel
components, field wiring and the motor. The breaker uses a solid state-
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