test Flashcards
Application purpose of DC 24 V onboard
Emergency systems, propulsion systems, nav and coms, alarms and monitoring
Working principle of DC Lead-acid battery
Electrochemical reaction, recharging, voltage output
PARALLEL At least, two advantages when compared to a single operation
increased reliability, efficiency, safety
PARALLEL Operating conditions and why voltage needs to be synchronised
Voltage difference, Frequency and or phase missmatch
Benefits of system grouping (with sub-panels)
safety, efficiency, maintanence
Types of switchgear can be divided into the following four groups
; switches / isolators / contactors / circuit breakers
Briefly discus the operation of each of these protection systems.
switch, manual on off, isolator dissconnects equipment, contactors electro mechanical switches (frequent use), circuit breaker shorts circuit
3 PHASE AC induction working principle with amperes
Magnetic field creation (3 phase ac passes througha stator creating rotating mag field, Electromag induction, RMF induces current, rotor motion
advantages and disadvantages of DC
ADV- Stable, easy storage DIS- high transmission loss
ADV DIS of AC
Easy voltage conversion efficient transmition DIS- complex system
Discuss why DC is difficult to change voltages.
DC lacks a time-varying component, making it incompatible with transformers
1ST STAGE GEN
Working principle with Fleming’s right hand rule
explain thumb force, first mag, middle current prime mover rotates rotor inducing AC
1ST STAGE Methods to control the magnitude of electricity production
speed regulation, Field excitation controll, load controll
3 phase rectifier Working principle
6 diodes in bridge shape alowing 1 direction current, AC is applied to rectifier, rectifier combines half cycles creating pulsing DC
Purpose of AC-DC conversion
compatability between systems, battery charging, smooth operation
2ND STAGE Working principle with Faraday’s law for single phase AC electricity
production
EMF is induced in condutor due to a change in magnetic Flux, magnitude of EMF is proportional to Flux, Rotator creates a change in flux, generates AC
DESIGN GENERATORS How many generators with what capacity should be arranged
two at 1500 one at 1000
DESIGN GENERATORS Discuss the reasons in economic / safety perspectives
fuel efficiency, maintanence cost, scalability, load sharing
CALC IMPEDANCE AND CIRCUIT CURRENT
XL= 2PIFL XC=1/2PIFC Z=ROOT R^2+XL^2+XC^2
CALC Vrms R,L,C
V=IR
CALC phase dif current supply voltage
theta=tan(XL/R)
CALC POWER FACTOR
COSTHETA
APPARENT POWER
S=V*i
CALC ACTIVE POWERN
P=i^2*R
Reactive power
Q=S×sin(ϕ)
