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Figure 1 3RW34 SIKOSTART Block Diagram Logic PCB. A
power supply on the logic printed circuit board accepts control
power (X1, X2) and provides power to the central processing unit
(DSP), support circuitry, and cooling fan(s). The input coil termi-
nals (A1, A2) are for commanding the motor to RUN and STOP .
6
Figure 1
The three sets of numbered output terminals are for customer
control devices related to Motor Running (e.g., start / stop
devices), Motor Running at Full Voltage (e.g., to drive a bypass
contactor), and Fault (e.g., phase loss or shorted SCR).
Setup Controls. Setup controls are connected to the logic board
but are accessible from the controller's front cover. Three poten-
tiometers provide customer adjustments: T1 - the rate of the
voltage rise (accel ramp time); U - the initial motor start voltage;
and T2 - decel ramp time for a soft stop (pump stop).
A dip switch (SW1, figure 20) is used to set the controller soft-
ware to the proper application. The functions set are:
1. delay at stop: when bypass contactor is used.
2. delay at start: when isolation contactor is used.
3. motor type: wye (star) or delta
4. Fault output: opens or closes on fault.
2.3 Three-phase Systems
Since the controller can be used with either wye or delta
motors, a brief discussion of currents and voltages for three-
phase wye and delta arrangements with balanced loads is
included here as an aid to understanding controller setup pro-
cedures and to assure proper controller selection.
Figure 2 shows the voltage waveforms for a three-phase system
of three equal voltages separated by 120-degree phase angles.
The voltage in phase a, or Ua, leads the voltage in phase b, or
Ub, by 120v. Likewise, Ub leads Uc by 120v, and Uc leads Ua by
120v.
Figure 2 - Basic Three-phase Waveforms
Siemens Energy & Automation, Inc.
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