Schweitzer Engineering Laboratories SEL-701 - Start and Emergency Restart Logic; Figure B.7 Start Logic

Date Code 20010719 701 Motor Protection Relay
SELOGIC
®
Control Equations & Relay Logic
Start and Emergency Restart Logic
B.23
Start and Emergency Restart Logic
Figure B.7 shows the logic the relay uses to initiate motor starts.
Figure B.7 Start Logic.
If the Trip output contact is not asserted, the relay asserts the START Relay Word
bit in response to any of these conditions:
 The Motor Start SELOGIC control equation (STR) result
is true (logical 1).
 The Emergency Restart Relay Word bit asserts.
 You execute the STR serial port command or a Modbus Start control
command.
The START Relay Word bit remains asserted for 0.5 seconds, unless the relay
trips. If the relay trips before the 0.5 second timer expires, the relay resets the timer,
clearing the START Relay Word bit.
The Motor Start SEL
OGIC control equation allows you to define a logical
condition that initiates a motor start.
EXAMPLE B.1 Initiating a Motor Start Using a Relay Contact Input
You can use a relay contact input such as IN6 to initiate motor
starting. Set the SEL
OGIC control equation STR = IN6. Connect the
normally open pushbutton contact to relay terminals C08 and C09
(IN6). Program an output contact to close when the START Relay
Word bit asserts, as shown in Program an Output Contact for Motor
Starting on page B.24. When you push the button, IN6 is asserted,
asserting the START bit, closing the output contact, and initiating
the start.
TRIP
Reset
START
0
0.5 s
STR =
EMRSTR =
START =
TRIP =
Motor Start SEL
OGIC Control Equation
Emergency Restart SEL
OGIC Control Equation
Initiate Motor Start Relay Word Bit
Trip Output Contact Is Asserted
STR
EMRSTR
STR Serial Port
Command