7SR11 & 7SR12 Description Of Operation
ยฉ2017 Siemens Protection Devices Limited Chapter 1 Page 21 of 88
TEST/RESET๏ด button. The push buttons are recessed in housings to prevent accidental operation
and small enough that the fascia data is not obscured. Some users may prefer to use a suitable blunt
stylus for pressing buttons if operation is difficult.
Figure 2-5 Relay with transparent cover and push buttons
2.4 Power Supply Unit (PSU)
Five variants of the relay PSU can be ordered:
G * 80V - 250V DC
19V DC
M 24V - 250V DC
19V DC
N 24V - 250V DC
88V DC
* Option G will also work with a nominal Auxiliary Voltage and Binary
Input Voltage of 115 V rms.
Table 2-2 Power Supply Unit (PSU) options
The rated auxiliary supply voltage (Vx) is clearly stated on the relay fascia rating label, see below.
7SR1 devices manufactured before February 2012, prior to hardware version /CC, cannot be operated from AC
supplies and the rating is shown as DC only. From hardware version /CC, option G devices are available which
will operate normally for DC or AC supplies. These 80-250 V DC/110/115 V AC devices of hardware version /CC
or later will operate normally for reversed polarity DC auxiliary voltages โ devices of previous hardware versions
and 24-60V DC devices will not start-up with reversed polarity supplies.
All binary inputs are polarity conscious and will not operate if the DC supply polarity is reversed. For consistency
and safety it is advised that AC connections for auxiliary supply and binary inputs are made with the Live
connection to the +ve terminal and Neutral connection to โve.
In the event of the supply voltage level falling below the relay minimum operate level the PSU will automatically
switch itself off and latch out โ this prevents any PSU overload conditions occurring. The PSU is reset by
switching the auxiliary supply off and on.
The PSU does not contain any fuses or user serviceable protection components. For fuse rating see Chapter 5
Installation Guide.
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