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LATCHING SWITCH RELAYS
Series 24 LSR-Latching Switch Relay
Series 31 LSR-Latching Switch Relay
The electrical power industry has a great variety of requirements for latching type auxiliary
relays to provide maintained contacts -- both N/C and N/O. Often, manually operated switches
are used in conjunction with traditional relays to provide the "maintained" function. However,
traditional protective relays have limitations as to the number of contacts available and their
ability to withstand seismic vibration. Traditional auxiliary relays used in conjunction with the
protective relays also exhibit these limitations.
The LSR Latching Switch Relay was developed to meet these requirements. It is a two posi-
tion rotary action Latching Switch Relay that provides control of up to 20 N/O and 20 N/C
contacts in a single device. It is a manually or remotely operated unit used for a variety of
applications; latching relay, reclosing relay, programming relay, and local/remote
switch that is SCADA compatible.
NOTE: The Series 24 and 31 LSR Class 1E utility products comply with the following Nuclear
Standards: ANSI/IEEE C37.90, ANSI/IEEE C37.90.1, ANSI/IEEE C37.98, ANSI/IEEE
C37.105, ANSI/IEEE 323, ANSI/IEEE 344, ANSI/ASME NQA -1.
Series 24 and 31 Latching Switch Relays
Designed and manufactured to the highest standards in the
Qualified to UL, CSA, ANSI/IEEE
2 Size options - Series 24 and Series 31
Up to 20 N/O and 20 N/C contacts
Electric or manual operation
Available without handle for remote only operation
1E Nuclear qualified
Many Series 24/31 LSRs are available from stock for
The Electroswitch team of Customer Service and Applications
Professionals stand behind every Electroswitch product. Let us
put over 50 years of know-how to work for you!
Contact Deck Arrangement
The blade and terminal configuration enables the use of multiple contacts in the same
deck, and simple stacking procedures enable the fabrication of many independent contacts
in one relay. Specifically, two N/O contacts and two N/C contacts are provided in each
deck, and ten decks can be stacked, resulting in a relay with up to forty contacts. This deck
arrangement is illustrated in Fig 1.
The contacts operate reliably, using every contact and terminal illustrated. For good practice,
however, it is suggested that polarized voltages should not be used on adjacent contacts.
This is because of the remote possibility of flashover during transition between adjacent
contacts - especially at the higher DC ratings, or in highly inductive circuits.
The illustration of the basic deck LSR layout is for the first deck. For multideck units the sec-
ond digit of the terminal number is the same as the deck number.
As an example: Terminal 82 is in the eighth deck, in line under terminal 12 and is a N/O
contact used together with terminal 84.