GE Zenith ZTS Series - Manual (Page 2)

Electrical Ratings
• Ratings 40 to 4000 amperes
• 2, 3 or 4 Poles
• Open type, NEMA 1,
3R, 4, 4X and 12
• Available to 600 VAC,
50 or 60 Hz
• Suitable for emergency and
standby applications on
all classes of load, 100%
tungsten rated through
400 amps
• UL 1008 listed at 480 VAC
• CSA C22.2 No. 178
certified at 600 VAC
• IEC 947-6-1 listed at 480 VAC
Performance Features
• Contact transfer speed
less than 100 milliseconds
• High close-in and
withstand capability
• Temperature rise test per
UL 1008 conducted after
overload and endurance
tests - exceeds UL
requirements
• Available in ZTS (utility-
generator), ZTSU (utility-
utility), ZTSG (generator-
generator) and ZTSM
(manual) configurations
Design and
Construction Features
• Double throw,
interlocked operation
• Electrically operated,
mechanically held by a
simple, over-center
mechanism
• Segmented silver tungsten
alloy contacts with
separate arcing contacts
on 225 amp and above
• Arc quenching grids,
enclosed arc chambers,
and wide contact air gap
for superior source-to-
source isolation on all units
• Control circuit disconnect
plug and drive inhibit
switch for safe maintenance
• Components accessible
for inspection and
maintenance without
removal of the switch
or power conductors
• Mechanical indicator and
contact chamber cover
designed for inspection,
safety and position
designation
The
ZTS Series
is the building block
of our transfer switch product line.
This ruggedly built power contactor
family of switches has been specifically
designed for transfer switch duty with
dependability, versatility and user
friendliness of prime concern.
ZTS switches are available in open type construction
for switchboard installation or NEMA enclosed to
the customer’s specifications. The power panel
components, consisting of power switching contacts,
drive mechanism and terminal lugs, are mounted
on a specially formed panel. Logic devices including
microprocessor control auxiliary time delays and
special accessory equipment are assembled on the
door for ease of maintenance and separation from the
power section. They are connected with a numbered
wiring harness equipped with a disconnect plug that
allows isolation of the control panel for maintenance.
ZTS Series Method of Operation
When the normal source voltage fails or drops to a
predetermined point (usually 80% of nominal), if
required, a circuit is closed to start the engine
generator set. When the emergency source reaches
90% of rated voltage and 95% of rated frequency, the
drive solenoid is energized through the emergency
coil control relay, causing the main contacts to
disconnect the load from the normal source and
connect it to the emergency source. After the drive
solenoid has completed its electrical stroke and is
seated, the emergency coil control relay opens to
disconnect it. The transfer switch is now mechanically
locked in the emergency position.
When normal voltage is restored to a predetermined
point (usually 90% of nominal), the control voltage
sensing energizes. The normal side coil relay closes,
and after the drive solenoid has completed its electrical
stroke and is seated, the coil control relay opens to
disconnect it. The transfer switch is now mechanically
locked in the normal position.
Drive Mechanism
All
GE Zenith ZTS switches employ the simple “over-
center” principle to achieve a mechanically locked
position in either normal or emergency and
GE Zenith’s
high speed drive assures contact transfer in 100 ms
or less. High contact pressure and positive mechanical
lock allow for high withstand and closing ratings, far
exceeding
UL requirements. All ZTS units are listed with
UL umbrella breaker, severe breaker and current
limiting fuse ratings.
ZTS Series
Automatic Transfer Switches
Neutral Switching
The
GE Zenith ZTS Series is available in true four pole
designs for multi-source power systems that require
neutral switching. The neutral contact is on the same
shaft as the associated main contacts. This ensures
positive operation, and avoids any possibility that
the neutral contact will fail to open or close, as is
possible when the neutral pole is an add-on accessory.
The neutral contacts are identical to the main contacts,
having the same current carrying and high withstand/
closing ratings as the mains. They are designed to
break last and make first to reduce the possibility of
transients while switching the neutral.
Safe Manual Operation
The
ZTS manual operator consists of a large, easy-to-use
handle that fits securely for manual operation during
installation and maintenance or in an emergency.
The ZTS may be provided with an operator inhibit
switch to disconnect the electrical drive prior to
maintenance. Fully enclosed wrap-around arc covers
shield the main contacts and mechanical components,
preventing operator exposure during manual operation.
Transferring Large Motor
or Highly Inductive Loads
Some loads, especially large motors, receive severe
mechanical stress if power is trans-ferred out of phase
while the motor is still rotating. Also, back
EMF gener-
ated by a motor may result in excess currents that
can blow fuses or trip circuit breakers.
GE Zenith
offers four solutions to these problems:
PB-5066 • P age 2
1. Universal Motor
Disconnect (UMD): This load
control disconnects a large
motor via its control circuit
for an adjustable period of
time prior to transfer in either
direction. For switching multiple
motors, GE Zenith Accessory A62
disconnects the motors prior to
transfer and brings them back
on line sequentially.
2. Accessory R50: This is an
in-phase monitor that compares
the phase angle between both
sources of power and prevents
transfer until the two are approxi-
mately in phase (within a self
adjusting range). GE Zenith’s
high speed transfer action
coupled with the MX series
microprocessor control logic
ensure closures at or near
zero degree phase difference.
3. Series ZTSD : GE Zenith
offers delayed transition
switching on transfer switches
rated 40 amperes and above –
the GE Zenith ZTSD Series. This
programmed center-off position
allows for the full decay of
rotating motors or transformer
fields. It can also be used for
load shedding of selected
circuits or other appli-cations
which require a means to
disconnect the load from either
source. Major UPS system manu-
facturers recommend delayed
transition switches for proper
restart sequencing of their systems.
4. Series
ZTSCT : GE Zenith’s
series of closed transition switches
combine ZTSD operation during
a source failure with a highly
engineered control system that
allows momentary paralleling
(100 ms) of two acceptable
sources, thereby limiting the
impact of transfer on the load.