COMMUNICATIONS GUIDE
MODBUS MEMORY MAP
469 MOTOR MANAGEMENT RELAY – COMMUNICATIONS GUIDE
17
Phase CT
The setpoint in modbus register 1180 provides an external factor for calculating phase
current.
Let A represent external scale, where A = value of register 1180.
Let B represent internal scale, where B = 500 for Phase current on SR469.
SF
current
= A/B.
Ground CT (type 1A Secondary or type 5A Secondary)
The setpoint in modbus register 1183 provides an external factor for calculating ground
current.
The setpoint in modbus register 1182 has value 1 or value 2, indicating 1A or 5A secondary.
Let A represent external scale, where A = value of register 1183.
Let B represent internal scale, where B = 500 for Ground current on SR469.
SF
current
= A/B.
Ground CT (type Multilin CT 50/0.025)
The setpoint in modbus register 1182 has value 3, indicating Ground CT type Multilin CT.
Let A represent external scale, where A = 1 Ampere.
Let B represent internal scale, where B = 500 for Ground current on SR469.
SF
current
= A/B = 0.002 Ampere
Phase Differential CT
The setpoint in modbus register 1185 provides an external factor for calculating phase
differential current.
Let A represent external scale, where A = value of register 1185.
Let B represent internal scale, where B = 500 for Phase Differential current on SR469.
SF
current
= A/B.
Phase VT
The setpoint in modbus register 11A1 provides an external factor for calculating phase
voltage. The scale factor is:
Let A represent external scale, where A = (120 Volts) * (value of register 11A1).
Let B represent internal scale, where B = 2500 for Phase voltage on SR469.
SF
voltage
= A/B.
Table 3: SR469 Internal Units per Channel
1185
Differential CT primary
Current [Ampere]
11A1
Voltage ratio
Ratio [n:1]
Channel
number
Input wiring
Internal
units scale
Nominal
Unit
External Scale factor
SF
current
or SF
voltage
Modbus
register
0
Phase A current
500
1 x CT
CT primary /500
1180