ABB RELION REX640 - Max current selector; Rotor resistance calculator

The ambient temperature TEMP_AMB is available in the monitored data view.
The Env temperature Set setting is used:
• If the ambient temperature measurement value is not connected to the
AMB_TEMP input in ACT.
• When the ambient temperature measurement connected to RPTTR is set to "Not
in use" in the RTD function.
• In case of any errors or malfunctioning in the RTD input.
Max current selector
Max current selector selects the highest measured True RMS phase current and
reports it to Thermal level calculator.
Rotor resistance calculator
The module calculates rotor resistances as a function of estimated slip. Slip
estimate is based on the measured phase currents and line voltages.
Necessary initial values for slip estimation are rotor resistance at locked rotor and
rotor resistance at nominal speed, calculated with following equations. Settings
mentioned in equations can be found from the motor datasheet information.
= 1 −
(Equation 48)
R
N
is the rotor resistance at nominal speed,
RPM
N
is the setting Nominal speed and
RPM
S
is the setting Synchronous speed.
=
2
(Equation 49)
R
L
is the rotor resistance at locked rotor,
T
L
is the setting Relative starting torque and
I
L
is the setting Relative starting current .
In addition to R
N
and R
L
, the slip estimate calculation uses line voltages and phase
currents to calculate the apparent total resistance and the initial stator resistance.
=
1.2∙
(
)
−
( )
(Equation 50)
S is the motor slip,
R is the apparent total resistance calculated from line voltages and
phase currents,
Table continues on the next page
Protection functions 1MRS759142 F
428 REX640
Technical Manual