DGC Brushless Excitation - Emerson Process Management

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DGC Brushless Excitation System Description For WTA retrofits, the Integrated Power Amplifier incorporates the functionality of the Firing and Power drawers into one drawer. The Firing Drawers are removed and discarded and the Power Amplifiers are replaced with new Integrated Power Amplifiers. The Integrated Power Amplifier has the same form and fit as the existing WTA Power Drawer, utilizing the existing racking mechanism and bus-bar connections in the rear. A new cable and connector arrangement is installed to support the other needed connections. For all other applications, the Power Amplifier components are panel mounted. The panel dimensions and bolting patterns are designed to facilitate installation into a variety of existing cabinet configurations. The Power Amplifier Panel is typically constructed with redundant SCR Bridges; however, single channel panels are available. Panel Mounted Power Amplifier 3.7 Field Breaker The DB25 (or DB15) Field Breaker is replaced with a Square D MasterPac breaker assembly which is configured as a form, fit and function retrofit. The new breaker assembly adapts to the existing rails with a carriage that becomes a permanent part of the cubicle. The MasterPac breaker carriage is permanently mounted inside the adapter carriage. The MasterPac breaker racks into its own carriage and provides the same functionality as the existing breaker. 3.8 Control Switches and Indications The design of the DGC Excitation System is such that the operation of the new voltage regulator is largely unchanged from the old regulator. The control room interfaces are retained and their functionalities are nearly identical. 3.8.a Field Breaker Control Switch The Field Breaker Control Switch (41CS) allows the operator to close the 41Breaker (contactor) to initiate excitation. The actual position of the 41 device is indicated with lamps. 3.8.b Regulator Mode Control Switch The Regulator Mode Control Switch (90CS) is a three-position switch that allows the operator to select the operating mode of the regulator. The actual operating mode is indicated with three lamps. The state of the lamps is controlled by digital outputs from the DGC. © Emerson Process Management Power & Water Solutions. - 12 - PWS_005075 [3]
DGC Brushless Excitation System Description 3.8.c Voltage Adjuster Control Switch The Voltage Adjuster Control Switch (90VCS) is used to establish the terminal voltage setpoint for the voltage regulator. The range of the switch is typically calibrated for 90% to 110% of the generator’s rated voltage. The Voltage Adjuster Control Switch position is indicated on an analog meter, driven by an analog output signal from the DGC. In the absence of a meter, the position may be indicated with a set of lamps. Digital outputs are available to drive indicating lamps or for status indication of the voltage adjuster position. The Voltage Adjuster Control Switch has “pre-position” capabilities that allow the adjuster to be forced to a specified position upon request. 3.8.d Base Adjuster Control Switch The Base Adjuster (PAR) provides control of excitation when not in automatic voltage control. The Base Adjuster is typically calibrated for the full range of power amplifier conduction which results in zero to maximum amps of field current. The Base Adjuster position is indicated on an analog meter, driven by an analog output signal from the PAR. In the absence of a meter, the position may be indicated with a set of lamps. Digital outputs are available to drive indicating lamps or for status indication of the voltage adjuster position. The Base Adjuster has “pre-position” capabilities that allow the adjuster to be forced to a specified position upon request. The Base Adjuster operates in a “follower” mode when the DGC is in automatic control. This is a significant safety feature because the Base Adjuster will always be adjusting its output to bring the output of the regulator back to zero. The practical result is that if the regulator experiences a failure or is restricted from producing a regulator output, the Base Adjuster will maintain the generator voltage at the same level. The PAR alarm output is monitored by the DGC as a condition that will generate an alarm. This alarm is usually configured to generate the DGC Trouble Alarm output. 3.8.e Regulator Output Meter The Regulator Output Meter in the control room provides indication of the control signal value when it is not in the OFF mode. The Regulator Output Meter signal is the final control signal of the DGC. It is supplied to the firing circuits to control the amount of excitation current supplied to the Generator. Since the reliability of the Regulator Control Output Meter is critical to the operation of the DGC, the signal is selfmonitored by the DGC to ensure that it is operable and accurate. 3.9 Feedback Signals The DGC requires several Feedback Signals in order to provide control and protection for the generator. 3.9.a Generator Terminal Voltage Generator Terminal Voltage is the principle feedback signal for controlling the generator. The signal is taken from the Regulator PT’s. It is also used as an input to the Limiters and Protection features. © Emerson Process Management Power & Water Solutions. - 13 - PWS_005075 [3]
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DGC Brushless Excitation - Emerson Process Management

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