Technical information

6 – APPLICATIONS
Inside Delta Connected Motor
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6.1.2 Inside Delta Connection
An inside delta soft starter is shown in Figure 11, where the power poles are connected in series with the stator windings of a delta
connected motor.
Figure 11 – Typical Inside Delta Motor Connection
Motor
2
5
3
6
1
4
T6 T3
T4
T1 T5
T2
L3
L2
L1
For an Inside Delta connected motor, the inside winding’s average SCR current is less than that of the outside average line current by
a factor of 1.55 (FLA/1.55). By comparison of Figure 10 and Figure 11, the most obvious advantage of the inside delta starter is the
reduction of current seen by the soft starter. The soft starter current rating 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
6.2 Other Applications using the MX
The MX has been designed to be the controller for other motor control applications, such as Wye Delta, Across the line full voltage
starter, Phase Control/Voltage Follower and Current Follower. In each case, the MX is providing the motor protection and the
necessary control for these applications.
6.2.1 Wye Delta
When the Starter Type parameter is set to Wye-Delta, the MX is configured to operate an electromechanical Wye-Delta (Star-Delta)
starter. When in Wye-Delta mode, all MX motor and starter protective functions, except bad SCR detection and power stack
overload, are available to provide full motor and starter protection. The Up To Speed Time parameter sets the time when the Wye to
Delta transition occurs during starting.
The MX can operate two configurations of Wye-Delta starters, open transition and closed transition.
An open transition starter momentarily disconnects the motor from the input line during the transition from Wye to Delta
operating mode.
A closed transition starter uses resistors that are inserted during the transition so that the motor is never completely
disconnected from the input line.