Allen-Bradley PowerFlex 755 User Manual page 151

Table 47 - Advanced Reaction Connection Time Limit Configuration Settings
Advanced Reaction
Connection Time
Description
Limit Configuration
Settings
The RPI specifies the period that data updates over a connection. For example, an input
module produces data at the RPI that you assign. For safety input connections, you can set
the RPI on the Safety tab of the Module Properties dialog box. The RPI is entered in 1 ms
increments, with a range of 6...500 ms. The default is 10 ms.
The Connection Reaction Time Limit is adjusted immediately when the RPI is changed via
Requested Packet
the Logix Designer application.
Interval (RPI)
For safety output connections, the RPI is fixed at the safety task period. If the
corresponding Connection Time Reaction Limit is not satisfactory, you can adjust the
safety task period via the Safety Task Properties dialog box of the safety controller. See the
user manual for the controller.
For typical applications, the default RPI is sufficient.
The Timeout Multiplier determines the number of RPIs to wait for a packet before
declaring a connection timeout. This value translates into the number of messages that
can be lost before a connection error is declared. For example, a Timeout Multiplier of 1
Timeout Multiplier
indicates that messages must be received during each RPI interval. A Timeout Multiplier
of 2 indicates that one message can be lost as long as at least one message is received in
two times the RPI (2 x RPI).
The Network Delay Multiplier defines the message transport time that the safety protocol
enforces. The Network Delay Multiplier specifies the round-trip delay from the producer to
the consumer and the acknowledge back to the producer. You can use the Network Delay
Network Delay
Multiplier to reduce or increase the Connection Reaction Time Limit in cases where the
Multiplier
enforced message transport time is significantly less or more than the RPI. For example, to
adjust the Network Delay Multiplier is helpful when the RPI of an output connection is the
same as a lengthy safety task period.
The Connection Reaction Time Limit is the maximum age of safety packets on the
associated connection. If the age of the data that is used by the consuming device exceeds
the Connection Reaction Time Limit, a connection fault occurs. The following equations
determine the Connection Reaction Time Limit:
Connection Reaction
Time Limit Input Connection Reaction Time Limit = Input RPI x [Timeout Multiplier + Network Delay
Multiplier]
Output Connection Reaction Time Limit = Safety Task Period x [Timeout Multiplier +
Network Delay Multiplier - 1]
IMPORTANT If the drive is used with an induction motor, there is a general rule of no
repeated (three or more) start/stops with less than 10 seconds between
them (assumes the highest RPI of 500 ms is used). Otherwise a safety
connection loss can occur. If less than 10 seconds is needed, a lower RPI can
be used per the following formula:
RPI (ms) * 19 = Min. Repeated Start/Stop time (seconds)
For example, a 50 ms RPI equates to a minimum of 0.95 seconds required
between repeated start/stops.
6. Click Apply.
Rockwell Automation Publication 750-UM005A-EN-P - October 2018
Integrated Motion – Configuration, Programming, and Operation Chapter 7
151