Main ac Power System

The onsite ac power system (ECS) is a non-class IE system comprised of a normal, preferred, maintenance and standby power supplies. The normal, preferred, and maintenance power supplies are included in the main ac power system. The standby power is included in the onsite standby power system. 

An important attraction of all of these fuel cell systems, both as main vehicle power systems and as APUs, is their ability to support the new wave of vehicle electronics that is being introduced. New or planned electronic gadgetry on vehicles includes navigation systems extensive on-board communications voice-actuated controls exterior alternating current (ac) power supplies computer-controlled, power-... 

The plant model includes eight different safety systems that are mostly four-redundant. The safety systems are divided into two separate subsystems Reactor Protection System (RPS) and Diverse Protection System (DPS), which are implemented on different automation hardware. The RPS safety systems are automatic depressurisation system (ADS), component cooling water system (CCW), emergency core cooling system (ECC), service water system (SWS) and residual heat removal system (RHR). The DPS safety systems are emergency feed water system (EFW), and main feed water system (MFW). In addition, the AC power system belongs to both RPS and DPS. The model describes the operation logic of the safety systems, the hardware equipment used to implement each system, and the associated failure modes for each piece of equipment. 

Offsite power, main ac power, and onsite standby power systems. 

The ECCS and CSS installed in conventional PWRs are eliminated. The residual heat removal system (RHRS), CCWS, ESWS, emergency AC power system, and heating, ventilating, and air conditioning (HVAC) system of the main control room are designed as non-safety grade, since the SDHS directly removes decay heat from core to the atmosphere through the SGs without operator actions or external supports such as power, water, etc. 

Electric power should be available from two highly reliable sources. The usual arrangement is an alternating current (AC) power supply, with trickle charger supplying an emergency battery system. Batteries should be sized for loss of primary power for a period of no less than 8 hours, and for at least 12 hours if the supply is not reasonably reliable. An exception is power for alarm bells or horns, which require only 1 hour of emergency power. The power supply should be monitored by a power-on lamp on the control panel and a main power failure alarm. 

Reference 2 also describes the on-off characteristics of the power semiconductors used in the bridges e.g. diodes, thyristors, triads, gate turn-off thyristors and bipolar power transistors. Only the steady state operations of bridges are described herein. For such operations it is assumed that the load is well matched to the rating of the bridge. The remainder of this section is an introduction to the subject of harmonic voltages and currents that are caused by variable speed systems for DC and AC motors. It emphasises the main aspects that affect the supply power systems. 

The electrical generation system (see Fig. 1.11) provides AC power to four independent MAIN power busses (MAIN AC BUS 1, 2, 3 and 4) and an ESSENTIAL AC BUS (ESS AC). The Essential Bus can be connected to either AC BUS 3 or 4 to provide a reversion capability in the event of a Number 3 or 4 generator failure. If both these generators should fail, then the ESSENTIAL Bus can be powered from the ESSENTIAL DC (ESS DC) Bus via the Emergency Inverter (EMERINV). 

A shutoff valve is used in each steam line outboard of the external containment isolation valve and fimctions as a backup to the isolation valve. The shutoff valve is part of leakage control system to prevent possible release of nuclear steam which could leak through the main steam containment isolation valves following a LOCA. Independent contairunent inboard and containment outboard divisions are used to establish a pressurized barrier between the containment barrier and the environs. Out leakage is effectively eliminated and in leakage is directed into the containment from the pressurized volume. Both divisions are powered from auxiliary and standby AC power. While either of the two divisions is sufficient to establish the necessary pressure barrier, both are initiated in the control... 

FIGURE 10.176 The dual utility feeder system of AC power loss protection. An automatic transfer switch changes the load from the main utility line to the standby line in the event of a power interruption. 

Isolates the HVAC penetrations in the main control room boundary on high-high particulate or iodine concentrations in the main control room supply air, or when the pressurizer pressure falls below the low setpoint, or on extended loss of ac power to support operation of the main control room emergency habitability system. 

Power is supplied to the main control room/control support area HVAC subsystem by die plant ac electrical system. In the event of a loss of the plant ac electrical system, the main control room/control support area ventilation subsystem can be transferred to the onsite standby diesel generators. The convection heaters and duct heaters are not transferred to the onsite standby diesel generator. 

When controlling SOFC systems, the main control parameter is the electrical power output of the system. This AC output is determined by the inverter connected to the SOFC stack. The fuel supply to the stack must follow the DC power demand by the inverter, which is needed to deliver the required AC power. This is more complicated than controlling gas turbines, whose power output is related directly to the fuel flow. In the case of a SOFC/GT hybrid system, power control is even more complicated since both the gas turbine generator and the SOFC stack deliver power. A major concern in load following is the risk of retaining residual unburned hydrogen and carbon monoxide in the stack, due to a sudden load drop [3 5], which can be difficult to handle. 

So where does soft-start really help Mainly in bringing up the output voltage rail smoothly, maybe to avoid jerking the system connected at the output of our power supply. Yes, perhaps within a certain range of output C and L, it can also help control the stresses on the switch at power-up. But that support is hardly unconditional. Maybe it helps somewhat in lowering the overshoot of the rail at startup. But as mentioned in Question 2, it can itself be a reason for the overshoot too. Therefore, in all the AC-DC Flybacks we... 

Commercially available combustible gas detection systems generally use 24 VDC as the power supply for field devices. 24 VDC is inherently safer and corresponds the voltages increasing used by most instrument systems in process areas. A main supply voltage converter can be used to step down or convert from AC to DC power supplies. 

---