McQuay RVSS14 Installation, Operation And Maintenance Manual page 38

reducing motor heating. If a Wye to Delta transition has not already occurred, a transition
will always occur when the complete UTS / Transition Time (QST 09, P9) expires.
The D3 control 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. The presence of these resistors in a closed transition starter
smoothes the transition from Wye to Delta operating mode. A typical closed transition Wye-
Delta starter schematic is shown in Figure 10.
For the Wye-Delta starter mode to operate properly, one output relay needs to be programmed
to the RUN output function and another output relay needs to be programmed to the UTS
output function. (Refer to parameters I/0 04-06, P42-44 for more information.)
Based on the typical closed transition schematic shown in Figure 10, Wye Delta Motor
Connection to the D3 Control, when a start command is given the starter will enter the Wye
starting mode by energizing the relay programmed as RUN.
The transition to Wye (Starting) mode occurs as follows:
1. Start command is given to the starter.
2. The RUN relay is energized which energizes the 1S contactor.
3. When the 1S contactor pulls in, the 1M contactor is energized.
The D3 starter will remain in the Wye mode until either:
1. The start command is removed.
2. The Transition Time (QST 09, P9) expires
The measured motor current is less than 85% of FLA and at least 25% of the Transition Time
(QST 09, P9) has elapsed.
3. A fault occurs.
When the Transition Time (QST 09, P9) expires, the starter will change from Wye starting
mode to the Delta or normal running mode by energizing the relay programmed as UTS. In
Delta mode, the RUN and UTS relays are both energized and the motor is connected in the
normal running Delta configuration.
The transition to Delta (Run) mode occurs as follows:
1. The Transition Time (QST 09, P9) expires
The measured motor current is less than 85% of FLA and at least 25% of the Transition Time
(QST 09, P9) has elapsed.
2. The UTS relay is energized which energizes the 2S contactor.
3. When the 2S contactor pulls in, resistors are inserted in the circuit and the 1S contactor is
DE-energized.
4. When the 1S contactor drops out the 2M contactor is energized.
5. When the 2M contactor is pulled in, feedback can be sent to the D3 control board to
confirm that the transition sequence to Delta is complete.
38
or
or
IOMM Starter