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Instruction Booklet IB020003EN
Effective January 2021
THE CAPACITORS ON THE RC SNUBBER BOARDS ARE HIGH-
VOLTAGE DEVICES. THEY CAN RETAIN A CHARGE FOR UP TO 15
MINUTES AFTER THE RVSS HAS BEEN SWITCHED OFF.
CARE MUST BE TAKEN TO ALLOW TIME FOR THE CAPACITORS
TO DISCHARGE BEFORE PERFORMING ANY DIAGNOSTIC
WORK ON THE POWER POLES, OR ENTERING THE UPPER OR
LOWER MV CELL.
6.3
Bypass contactor
Directly above the SCR truck, an AMPGARD three-pole vacuum
contactor rests on a shelf attached to the RVSS medium voltage cell
ceiling (see Figure 31).
This Bypass contactor is open during a start and closes when the
RVSS has determined that the start sequence is complete. When
it closes, each pole shorts around the SCRs in a phase Power Pole,
and the RVSS control electronics disables firing signals to the SCRS.
Figure 31. Shelf-mounted bypass contactor.
6.3.1
Bypass contactor rating
The Bypass contactor is rated for motor FLA current, not typical
starter inrush current, and is never used as a FVNR starter contactor.
6.3.2
Bypass mode
If needed, the RVSS system can be set to Bypass Mode. This mode
can provide an emergency alternative to soft starter operation. In
this mode, all RVSS SCR control functions are disabled, the Bypass
contactor is maintained closed, and the main contactor can be used
as a FVNR starter. This alternate operating mode should only be
used if the customer AC supply system and the connected load can
tolerate full voltage across-the-line starts.
6.4
Power supplies
The AMPGARD RVSS requires three internal power levels. These
power needs are provided by the CPT (control power transformer)
included in the RVSS cabinet, so that no external control power is
required for system operation. The CPT provides power for:
120 VAC single phase control power bus for MPR, DC power supplies, pilot relays,
•
Main and Bypass contactors, door indicating lights and space heaters.
RVSS control power is provided by the starter Control Power
Transformer (CPT), located in the Ampgard upper cell. This
transformer steps line voltage down to 120 VAC single phase,
and is rated based upon the customer project needs. The CPT's
primary and secondary windings are protected with fuses.
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The 120 VAC control bus powers a Motor Protective Relay (if
furnished), the control relays and starter contactor coils, the 24
VDC RVSS electronics power supply and 48 VDC power supply for
the SCR Power Pole Fan-out and Gate Driver boards.
24 VDC power for the RVSS electronics
•
RVSS electronics power is provided by a 24 VDC power located in
the RVSS low voltage compartment (see Figure 32). This power
supply accepts 120 VAC and delivers 24 VDC. It has an operation
status LED mounted on its front face. 24 VDC is supplied to the
Input/Output (I/O) Board, RVSS output relays RY1, RY2 and TRPX,
and the Base Control Module (BCM).
48 VDC power for the Power Pole firing Fan-out boards which further power the SCR
•
Gate Driver boards.
Power for the Fan-out Boards and Gate Driver Boards is provided
by a 48 VDC power supply located in the RVSS cell (see Figure
33). It is powered by the starter cell control power transformer
that powers the starter control bus (see Figure 11). It has an
operation status LED mounted on its front face.
Figure 32. 24 VDC power supply.
Figure 33. 48 VDC power supply.
6.5
Optional motor protective relay
The AMPGARD RVSS can be furnished with one of a variety of
motor protective relays (MPR). When furnished, such relays are
mounted in the starter low voltage cabinet door, in one of the
cutouts provided for the purpose.
AMPGARD RVSS
Reduced Voltage Soft-Starter
User Manual
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