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Diagnostics Optimization CT MODBUS RTU Technical Data
E300 Design Guide 207
Issue Number: 1
Motor Percentage Flux (B18) gives an indication of the flux level in the motor where a value of 100 % is equivalent to the rated flux level for the motor.
Thermal Protection Mode (B19) defines the action taken by the drive when Motor Protection Accumulator (J26) reaches 100 % and/or Percentage Of
Drive Thermal Trip Level (J79) exceeds 90 %. The bits in Thermal Protection Mode (B19) are defined as follows:
The required current limit is derived from Symmetrical Current Limit (B16). The current limit can be further limited by current limit on motor overload
and/or drive temperature monitoring as shown below to give the Final Current Limit (J21).
Current limiting on motor overload
When the Motor Protection Accumulator (J26) reaches 100.0 % the current limit is limited to (K
1
– 0.05) x 100.0 %. This limitation is removed when
the Motor Protection Accumulator (J26) falls below 95.0 %. (K
1
is defined in the description of Motor Thermal Time Constant 1 (B20).)
Drive thermal monitoring current limiting
If Percentage Of Drive Thermal Trip Level (J79) exceeds 90 % the current limit is modified as follows:
Final Current Limit (J21) = Current limit x (100 % - Percentage Of Drive Thermal Trip Level (J79)) / 10 %
If both of the above attempt to reduce the final current limit the lowest calculated value of current limit is used.
This system has the effect of reducing the current limit to zero at the point where the drive should be tripped because its thermal monitoring has
reached a trip threshold. This is intended to limit the load on the drive to prevent it from tripping when supplying a load that increases with speed and
does not include rapid transients.
B18 Motor Percentage Flux
Mode RFC-A
Minimum 0.0 Maximum 150.0
Default Units %
Type 16 Bit Volatile Update Rate Background write
Display Format Standard Decimal Places 1
Coding RO, ND, NC, PT
B19 Thermal Protection Mode
Mode RFC-S
Minimum
0
(Display: 00)
Maximum
3
(Display: 11)
Default
0
(Display: 00)
Units
Type 8 Bit User Save Update Rate Background read
Display Format Binary Decimal Places 0
Coding RW
Bit Function
0
0 = Motor Too Hot trip is initiated when Motor Protection Accumulator (J26) reaches 100 %
1 = Motor Too Hot trip is disabled and current limiting on motor overload is active as described below
1
0 = Drive thermal monitoring current limiting is disabled
1 = Drive thermal monitoring current limiting as described below is active
Current limit modification
Motor thermal model
Motor Protection Accumulator
(J26)
Drive Temperature Monitoring
Percentage Of Drive Thermal Trip
Level (J79)
J21
Final Current
Limit
Current limit derived
from current limit
parameters
0
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