PROTECTION
Type VTT 11, 12
Definite Time Delay Relay
VTT is a static time delay relay which is particularly suitable for applications
requiring large number of operations and consistent accuracy with little or
no maintenance over long periods. It is also commonly used in industrial
processes.
Type VTT 11 units have a delayed pick- operation is maintained between 80% and
up, i.e., timing is started by closing an 115% of rated voltage.
initiating contact and the output relay is
energised at the end of the set time. The Timing ranges
Features
unit resets when the initiating contact is Models with the following setting ranges
Consistent accuracy reopened. (in seconds) - continuously adjustable -
Reliability are available:
Low burden Type VTT 12 units have a delayed drop-
Reduced maintenance off, i.e., the output relay is normally 0.05 - 0.5
Immunity to transients and surges; energised. Timing is started by opening 0.10 - 1.0
withstands 5 kv impulse voltage test an initiating contact and the output 0.50 - 5.0
Relays with heavy-duty magnetic relay is deenergised at the end of the set 1.00 - 10.0
blow-out contacts also available time. The unit resets when the initiating 2.50 - 25.0
contact is reclosed.
Description Accuracy
A stabilised voltage is applied to a Technical data Within 5% of setting or 10 milliseconds
resistance/capacitance circuit. The whichever is greater, at nominal voltage
potential developed across the capacitor Voltage ratings and at an ambient temperature within
is applied to a transistor switching circuit the range of 10C and 30C.
DC supply
which, in turn, operates an attracted
armature relay when the potential Within 5% of setting or 25 milliseconds
30, 48, 110 or 220V. Satisfactory
reaches the trigger level. whichever is greater for supply voltage
operation is maintained between 70% and
The time delay is varied by altering variation for 30%. Operating temperature
130% of rated voltage.
the resistance value in the resistance/ range -5C to +50C.
capacitance circuit by a potentiometer Units for use on 110 or 220V are supplied
calibrated in seconds. A circuit is with a suitable external resistor.
incorporated to protect the transistors
from damage due to high peak transients AC supply
in the supply voltage. A diode is also fitted Customer Benefits
in the circuitry to take care of inadvertent 110, 240 or 415V at 50 Hz. Relays Accurate and Reliable
connection of supply with reversed suitable for operation from ac supply Adjustable time delay
polarity. have a built-in power pack. Satisfactory Heavy duty magnetic blow
out contacts on request
GRID
1
Type VTT 11, 12
Type VTT with cover removed
Figure 1: Basic circuit diagram for VTT 11 relay
Figure 2: Typical connection diagram for ac VTT 11 relays
2
Type VTT 11, 12
Figure 3: Typical connection diagram for dc VTT 11 relays
Contacts
Four pairs of self-reset contacts in any
combination of normally open or normally
closed with a maximum of 2 normally closed
contacts are provided on the output attracted
armature unit of VTT 11 relays. Hand reset
contacts can be provided. For VTT 12 relays
three pairs of selfreset contacts with maximum
of 2 normally closed contacts are available.
Note
Relays with heavy duty magnetic blowout
contacts are also available on request.
Operation indicator
A hand reset mechanical flag operation
indicator can be provided on the output relay.
Insulation
The relay meets the requirements of IS-3231/
IEC 255-5 Series-C-2 kV for 1 minute.
3
Type VTT 11, 12
Impulse voltage
The relay complies with the requirements of IS-8686/
IEC 255-4, Appendix-E to Class III.
High frequency interference
The relay complies with IS-8686/ IEC 255-22-1,
Appendix-C to Class III.
Case
The VTT 11 and VTT 12 are supplied in 1/2N non-
drawout moulded cases suitable for flush mounting.
Non-drawout cases are finished bright black. Relays
can also be supplied in 1/2 N and 1D drawout cases
on request.
Burdens
(when energised)
DC Burden (W)
30V 1.26
110V 4.46
220V 9.1
AC Burden (VA)
110V 2.4
240V 2.3
415V 2.6
Dimensions and weights
Relay Maximum overall dimensions Approximate
Case size Height mm Width mm Depth* mm gross weight Kg
VTT11 or VTT12 1/2N Horz. 124 153 130 1.75
4
Type VTT 11, 12
Contact Ratings
Make and carry continuously Make and carry for 0.5 second Break
AC 1250 VA with maxima of 5A and 660V 7500 VA with maxima of 30A and 660V 1250VA with maxima of 5A and 660V
DC 1250 W with maxima of 5A and 660V 7500 W with maxima of 30A and 660V 100W (resistive) 50W (inductive)
maxima of 5A and 660V
Information required with order
1. Relay type (delay on pick-up or delay on drop-off)
2. Timing range
3. Voltage rating
4. Contact combination
5. Case
Figure 2 : Case and panel cut-out dimensions for case 1/2N (all dimensions in mm)
Figure 3 : Case and panel cut-out dimensions for case 1D (all dimensions in mm)
5
19/1, G.S.T. Road,
Pallavaram Works
Tel: 91-44-2264 8000
Fax: 91-44-2264 0040
www.grid.alstom.com
Tel.: +44 (0) 1785 250 070
ALSTOM T&D INDIA LIMITED
Pallavaram, Chennai - 600 043
http://www.alstom.com/contactcentre/
ALSTOM T&D Worldwide Contact Centre:
GRID
Alstom logo and any alternative version thereof are trademarks and service marks of Alstom. The other names mentioned, registered or not, are the property of their respective companies. The technical and other data contained in
the document are provided for information only. Neither ALSTOM, its officers nor employees accept responsibility for or should be taken as making any representation or warranty (whether express or implied) as to the accuracy or
completeness of such data or the achievements of any projected performance criteria where these are indicated. No liability is accepted for any reliance placed upon the information contained in this brochure. Alstom reserves the right to
6
Type VTT 11, 12
revise or change these data at any time without further notice.
