omentarily acts as a
generator) from one source to a second
source that is not in synchronism.
The time delay between opening
one set of contacts and closing the
other set is approximately 400 millisec-
onds. This may be extended by adding
a timer to the operator. The dual operator
transfer switch allows the motor loads
to be reenergized, after transfer, with
normal inrush starting current. It is
ideally suited for use where the electrical
load consists largely of three-phase
motor or inductive (transformer) loads.
The Industrys Highest 3-Cycle
Closing and Withstand Ratings
Russelectric transfer switches have
the highest 3-cycle closing and with-
stand ratings of any switches available
today (see chart).
These 3-cycle ratings mean that
Russelectric transfer switches are not
restricted to specific manufacturers
circuit breakers, but are fully rated and 2-, 3-, and 4-pole configuration Front accessible wiring Safe manual operator provides same
quick-break, quick-make operation as
motor operator Simple electrical operator Positive mechanical and electrical
interlocking Rapid arc quenching Quick-break, quick-make, high-speed
transfer mechanism
Russelectric Automatic Transfer Switches - Model RMTD
Russelectric automatic transfer switches
are modern, high-speed switching
devices designed to transfer electrical
loads from a normal power source to an
emergency power source when voltage
and/or frequency varies from preset
limits, and to retransfer loads when
normal power is restored.
The Russelectric automatic transfer
switch utilizes a high-speed, quick-break,
quick-make, preloaded transfer that is
accomplished by the use of a simple
electrical operator. The operator is
connected to the switch mechanism
through precision self-aligning, aircraft-
type ball joints which positively prevent
misalignment.
The entire line of Russelectric
transfer switches has been tested by
Underwriters Laboratories, Inc., and is
listed under UL Standard 1008.
Russelectric subjects its transfer switches to
the most comprehensive and demanding
performance test program, with close-in
and withstand short circuit ratings far
surpassing the minimum requirements
specified by UL-1008.
All transfer switches are thoroughly
inspected both mechanically and elec-
trically under simulated operating
conditions before shipment.
All bus bars are fabricated copper
and silver plated in accordance with UL
and ANSI standards. Enclosures are fab-
ricated with code gauge steel to meet
UL and other applicable standards.
© 1996 Russelectric Inc.
Positive Mechanical and
Electrical Interlocking
A rugged mechanical interlock
between the normal and emergency
contacts which positively prevents both
sources from being closed simultane-
ously. The switching mechanism posi-
tively prevents a sustained neutral posi-
tion, either electrically or mechanically,
during normal operation with either
source available.
Quick-Break, Quick-Make,
High-Speed, Preloaded Transfer
During transfer, the contact mecha-
nism is securely locked in position until
the overcenter position is reached. The
preloaded springs then instantaneously
open the closed contacts (quick-break)
and instantaneously close the open con-
tacts (quick-make) with a momentary
break in between. The quick-break fea-
ture provides for full arc interruption,
under maximum voltage and amperage,
in less than one-half cycle. This consid-
erably reduces contact erosion and
increases the useful life of the switch.
Rapid and Reliable Arc Quenching
The current interrupting chamber of
the Russelectric transfer switch consists
of parallel steel plates partially surround-
ing the contacts and enclosed by an
insulator. When the contacts open, the
arc drawn induces a magnetic field
which splits the arc into a series of
smaller arcs. The plates also conduct
heat away from the arc.
00-272 RMTD LAYOUT 4/23/02 2:17 PM Page 2 labeled for use with any manufacturers
circuit breaker with instantaneous trip.
These unrestricted ratings are extremely
important, since they allow engineers to
apply switches without problems of
coordination with different breaker types.
Underwriters Laboratories, Inc.,
requires a transfer switch to be able to
close in on the same amount of fault
current as it can withstand before they
allow it to be listed with a short circuit
rating. In view of this, fuse protection
becomes mandatory where extremely
high short circuit current is available.
All Russelectric transfer switches have
closing and withstand rating of 200,000
amperes when coordinated with current
limiting fuses.
Center-Off Switching Application
The Russelectric dual operator transfer
switch, when used to drive the switch
to a center-off position, is ideal for
sophisticated load shed control schemes.
For this reason, the dual operator switch
is often used with generator paralleling
systems. Furthermore, the center-off
position avoids false triggering and
latch-up of SCR devices when they are
transferred between two sources.
External Manual Operation
Optional external manual
operator provides manual
operation of the switch with
the protection of a fully
closed enclosure door.
Safe Manual Operator
The manual operator transfers the
switch with the same instantaneous
contact opening and contact closing
speed as the electrical operator. The
switching mechanism, whether electri-
cally or manually actuated, uses the
preloaded transfer principle that pre-
cludes the possibility of a flashover or
heavy arcing.
Front Connected Control
Components and Wiring
Control components and wiring can be
replaced without removing the transfer
switch from its enclosure.
Tracing of the electrical circuitry is
simplified by the neatly arranged, front-
connected, flame retardant, 600-volt SIS
switchboard wiring. Heavy-duty control
components and contacts are provided to
handle switching requirements.
All wiring connections are made
using crimped terminals and sleeve-type
marking labels.
Vertical-Type VS
Switchboard Construction
Control plates are available in narrow
widths for installation in switchboard
cubicles with either front or rear termi-
nals and/or bus tabs. Narrow widths are
available to fit motor control center
requirements (19 inches for capacities
to 800 amperes 3-pole). Special arrange-
ments are also available.
parameters, control the ATS, obtain
operational status, and set up optional
accessories.
The microprocessor board provides
memory management, two asynchronous
serial ports, battery backed real-time
clock, and microprocessor supervisor
(watchdog/power fail circuit).
Default setup information and cali-
bration data are stored on non-volatile
EPROM. Changes to default setup infor-
mation and calibration are stored on
EEPROM.
A rechargeable NIcad battery provides
5 VDC power to the controller during the
engine start timing cycle when no AC or
DC power is available.
Self-diagnostics perform periodic
checks of the memory, I/O, and commu-
nications systems, and invokes a software
reset if required when an error is detected.
A watchdog timer circuit invokes a hard-
ware reset if program execution exceeds
1.6 seconds.
The system contains 3-phase, over/
under voltage, over under frequency,
phase sequence detection and phase
differential monitoring for both normal
and emergency sources.
The controller uses industry standard
open architecture communication protocol
for high speed serial communications via
multidrop connection to other controllers
and to a master terminal.
The Accessory Setup and Service
Screens allow accessory installation and
changes to the system setup, calibration,
and diagnostic functions. A password is
required to limit access to qualified and
authorized personnel.
Microprocessor-Based
Control System
The Russelectric Model 2000 micro-
processor-based control system is prepro-
grammed at the factory to control all of
the operational functions of the automatic
transfer switch, including standard acces-
sories and optional accessories as speci-
fied by the purchaser.
The controller also senses the normal
source and emergency source voltages,
provides LED indicators to show
whether the ATS is in the normal or
emergency position, and also to confirm
that the CPU is running.
A 20-character, 4-line LCD display
and a 5 x 5 character tactile keyboard
allows easy access to the control system,
and is used to select items from main
and submenus, to set up adjustable
3-Cycle Closing and Withstand Ratings
RMS Symmetrical Amperes 480 VAC
Based on Testing Under UL-1008
Switch Rating
Closing and
Amperes
Withstand
100-400 42,000
600-800
65,000
1000-1200
85,000
1600-4000
100,000
00-272 RMTD LAYOUT 4/23/02 2:17 PM Page 3 Dimensions Open Style Switches
Notes:
1. Control components mounting plate required with all switches.
2. Switch can be furnished with load connections at top or bottom.
3. Switches are furnished with normal connection at top and emer-
gency at bottom. Positions may be reversed if desired.
4. Switch is designed for mounting in a nonventilated enclosure.
5. Standard wiring harness is 3 feet. Other lengths on request.
6. Fourth pole neutral on all 4-pole switches.
7. Lugs furnished on front-connected switches only. Lug quantity
and size data identical to corresponding enclosed switch lug data.
W
OH
H
D
W
D
H
OH
W
H
OH
30.00"
100
150
260
400
600
800
2 or 3
4
2 or 3
4
2 or 3
4
2 or 3
4
2 or 3
4
2 or 3
4
H
24.00
24.00
24.00