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Revision 8.6
SECTION 2 : SYSTEM DESIGN
20
Step 2
Calculate the mechanical power (P
m
) required by the motor. Use values of speed, load and efficiency of
the motion.
Step 3
Obtain the rotor current (R
A
) at determined
P
e
from motor manufacturers data tables.
Step 4
Calculate new R
1
A
R
1
A
= R
A
x
P
m
/ P
e
Step 5
Calculate the motors rotor resistance (
K
100
) that will give 100% rated torque at start. Obtain the motors
open circuit rotor voltage (
R
V
) from motor tables
K
100
=
R
V
/(√3
x R
1
A
)
Step 6
Determine the resistor values required from the selection table (refer to table 2-7). Figure 2-1 illustrates
the resistor configuration.
R1
TOT
= R1
R2
TOT
= R1 + R2
R3
TOT
=
R1 + R2 + R3
R4
TOT
=
R1 + R2 + R3 + R4
Figure 2-1 : Resistor Configuration
