BENSHAW RediStart MX3 Series, User Manual

Page: 175 / 238

7.7.2 Inside Delta Connected Starter
An inside delta connected soft starter is shown in Figure 50, where the power poles are connected in series with the stator windings of a
delta connected motor.
NOTE: Current Transformers MUST be installed to measure the full line current and never installed so they measure the current inside
the delta connection.
For an inside delta connected motor, the starter current is less than the line current by a factor of 1.55 (FLA/1.55). By comparison of
Figure 49 and Figure 50, the most obvious advantage of the inside delta starter is the reduction of current seen by the soft starter. The
soft starter can be downsized by a factor of 1.55, providing significant savings in cost and size of the starter.
An inside delta soft starter can also be considered for motors with more than 6 leads, including 12 lead dual voltage motors.
NEMA and IEC use different nomenclature for motor terminal markings, for 3 and 6 leaded motors.
NEMA labels motors leads, 1,2,3,4,5,6,
IEC labels motor leads, U1, V1, W1, U2, V2, W2
167
7 - THEORY OF OPERATION
Figure 50: Typical Inside Delta Motor Connection