What is the role of brushes in an AC generator?
It is more efficient to design an AC generator without brushes. However, some AC generators still use them. Brushes carry the current outside the generator.The rotor coils (windings) turn inside a stationary magnetic field which creates (induces) electrical current within the coils. The coils are connected to slip rings. The brushes “Brush” against the slip rings and make electrical contact with them. The slip rings turn, the brushes do not. The current is transferred from the slip rings to the brushes and from there to wires that carry the current to the outside world.The magnetic field in a brushless generator is produced by the rotor. The magnetic field turns with the rotor instead of remaining stationary. This has the same effect and electric current is produced in the stator windings which are stationary and no brushes are required. This is far more efficient than a generator with brushes.When a slip ring has parts that are electrically separated, it becomes a commutator. When the AC current in the generator alternates polarity, the commutator is positioned so that the change in polarity occurs as the brushes move from from one part of the commutator to the next. That prevents the current in the brushes from changing polarity. The result is a pulsed DC output instead of AC. That is the primary difference between an AC and a DC generator.
What is the start procedure from cold & dark state of a Boeing 737-800?
I'll cover procedures from initial electrical power-up through engine start. I'll omit taxi procedures and everything thereafter. We'll assume it's an APU start with no external power, start cart, or external air. Note that this is just the minimum amount of switchology you need to get the plane up and running — normally responsibilities would be split between captain and first officer, and there would be specific flows and checklists to be run. I'll also omit preflight planning aspects such as the takeoff and departure brief.Preflight Procedure (Battery and APU On)Battery — on.Standby power — on, guard closed.Alternate flaps master switch — off, guard closed.Wipers — off.Electric hydraulic pumps — verify off.Landing gear lever — down, lights on.Weather radar — off.Fire test and extinguisher test — perform.Left aft fuel pump (used by APU) — On.APU — StartAPU transfer bus — On.BUS OFF, TRANSFER BUS OFF, APU MAINT, APU LOW PRESSURE, APU FAULT, APU OVERSPEED lights — extinguished.Wheel well fire system — test.Lights — as desired.Recirculation fans — Auto.Packs — Auto.Isolation valve — Open.Engine bleeds — On.APU bleed — On.Engine Start (APU)Packs — off.Fuel pumps — On.Electric hydraulic pumps — On.Ignition switch — left.Left engine start knob — START position.When N2 reaches 25% or max motoring: Left fuel cutoff handle — Idle.Monitor EGT, oil pressure, and N1 for proper start indications.When left engine N1 stabilized, verify starter cutout and normal indications.Left engine start knob — Ground position.Repeat steps above for right engine.Before TaxiEngine generators — On.Probe heat — On.Packs — Auto.Isolation valve — Auto.APU bleed — Off.APU — Off.Engine start switches — AUTO (if available) or CONT(inuous).
How does a generator start?
Plenty of answers here on how to start a generator. Your question was “How does a generator start?”A generator or alternator is basically a coil of wire rotating or being rotated within a magnetic field. The magnetic field can be provided by permanent magnets. I suspect you were asking how does a generator start when there are no permanent magnets involved.In this case there are at least two coils, one of which produces the output power and the other the magnetic field. All well and good but how does that field exist before the generator starts?In an alternator one of the coils, the field coil for obvious reasons, can be initially exited by an external battery . This is how the alternator in your car works. Once the field is established and the alternator begins developing power some of this is diverted to the field coil and the batter y is no longer needed to maintain the magnetic field and is instead charged by the alternator.In a generator or alternator where no external excitation of the field coil is utilised, the residual magnetism of the iron core of the coils or surrounding environment usually provides a sufficient magnetic field to begin the process. If no such residual magnetism exists then the unit won’t work!Running a DC current through the field coil for a short while will provide the magnetic field required to start the generator/alternator and that magnetic field will now persist in the iron core after the unit is shut down.When negative earth vehicles became the norm, it was possible to reverse the polarity of an existing car generator by reversing the polarity of the field coils and connecting them across the battery for an instant. This reversed the magnetic poles of the iron core.
What are the uses of ac generator?
AC generators are a very common component in many applications, such as,automobiles, where they are known as alternatorspower generation from windmillspower generation from hydro-electric damsBasically AC generators have a couple of big advantages over DC generators:AC generators are cheaper to produceThe power they generate is easier to step up and down via transformersI believe these are the reasons that AC generators are the dominant technology in most applications.
What are the functions of AVR in a generator?
An automatic voltage regulator (AVR) is a electronic device for automatically maintaining generator output terminal voltage at a set value under varying load and operating temperature. It controls output by sensing the voltage Vout at a power-generating coil and comparing it to a stable reference.Most cheap portable generators have fixed excitation. In such machines, when an alternator is loaded, its terminal voltage drops due to its internal impedance. This impedance is formed of leakage reactance, armature reactance and armature resistance. The Vout also depends on the power factor of the load. That's why to maintain Vout within tighter limits, more expensive models use an AVR. Note that all AVRs are generally slow to respond to fast transient loads. Some high-end models, such as Honda EB10000 use more accurate digital DAVR.
How much will a 5000 watt generator power?
the fact of the matter is you can use about 4000 watts as a load and this will leave 1000 extra watts for the start up of your refrigerator. 5000 watts divided by 120 volts = 41.66 amps..you would have to use 1 #12 extension cord for each 20 amps being used.. so you would need 2 # 12 cords, both of these should be the heavy duty cords Your fridge should be on one cord by itself..and will need one half of the generators output just for the refrigerators best performance.. 20 amp start up at 120 volts is 2400 watts.once it starts the refrigerator will not use that much but it needs that much for its inrush start load. to find the combined load of every thing else multiply the volts times the amps to get the total watts should not be over 2500 watts for best performance of all items and to keep from overloading the generator. you should be able to power at least 10 60 watt bulbs, your laptop charger and your sump pump with the remaining wattage of your generator. you could also use the power strip with 8 outlets on this cord. just be sure you dont go over 20 amps with the second cord and everything will be fine.
Can I rewind a 95 Mustang Alternator to charge a 144v Electric Car main battery?
I've seen alternators, such as a prestolite 12v 140 amp, rewound with thinner gauge wire and with more winds and used as a regenerative brake (energized while coasting to use the car's forward motion to charge main battery pack) in electric vehicles. I was wondering if a 3G alternator from a 94-95 Mustang could be rewound the same way? What type of wire would I need to do this? What else, other than the actual stator rewinding, would need to be modified for this alternator to safely put out this high of voltage? Also, what effect would the original amp rating of the alternator have on the final result (they are available at 85, 130, 200, etc...)?
What are the different methods of starting synchronous motor?
“ Principle of Operation Synchronous MotorSynchronous motor is a doubly excited machine i.e two electrical inputs are provided to it. It’s stator winding which consists of a 3 phase winding is provided with 3 phase supply and rotor is provided with DC supply. The 3 phase stator winding carrying 3 phase currents produces 3 phase rotating magnetic flux. The rotor carrying DC supply also produces a constant flux. Considering the frequency to be 50 Hz, from the above relation we can see that the 3 phase rotating flux rotates about 3000 revolution in 1 min or 50 revolutions in 1 sec. At a particular instant rotor and stator poles might be of same polarity (N-N or S-S) causing repulsive force on rotor and the very next second it will be N-S causing attractive force. But due to inertia of the rotor, it is unable to rotate in any direction due to attractive or repulsive force and remain in standstill condition. Hence it is not self starting.To overcome this inertia, rotor is initially fed some mechanical input which rotates it in same direction as magnetic field to a speed very close to synchronous speed. After some time magnetic locking occurs and the synchronous motor rotates in synchronism with the frequency.Methods of Starting of Synchronous MotorMotor starting with an external prime Mover: Synchronous motors are mechanically coupled with another motor. It could be either 3 phase induction motor or DC shunt motor. DC excitation is not fed initially. It is rotated at speed very close to its synchronous speed and after that DC excitation is given. After some time when magnetic locking takes place supply to the external motor is cut off.Damper winding: In case, synchronous motor is of salient pole type, additional winding is placed in rotor pole face. Initially when rotor is standstill, relative speed between damper winding and rotating air gap flux in large and an emf is induced in it which produces the required starting torque. As speed approaches synchronous speed, emf and torque is reduced and finally when magnetic locking takes place, torque also reduces to zero. Hence in this case synchronous is first run as three phase induction motor using additional winding and finally it is synchronized with the frequency.” Synchronous Motor Working Principle