Why Armature is place on Stator in Synchronous machines

In case of synchronous machines  Armature is always placed on stator and field winding on armature as there are following advantages:-
1.     Better economy:-
It is always economical to place armature winding on Stator and field winding on rotor in synchronous machines as this can be illustrated by example as below:-

Consider a 3-Phase Star connected 500 MVA, 11KV synchronous machine, now its line current will be = 500X103
                               11 X
Which Will be = 26244 A
Now If we place armature winding on rotor than we will required 3 slip rings each will be capable of handling such a high current of 26244A. Further Slip rings needed to be insulated from shaft for a voltage= 11/ = 6.35 KV.
Also Star point needed to be brought out by using fourth slip ring which will be grounded through a resistance.

Now consider a case where we will place field winding on rotor and armature winding on  Stator, in that case field winding need to handle lower current and voltages.  Now consider 2 MW at 500V then current required to handle field current of= 2000/0.5= 4000A . So we needed 2 brushes to handle 4000A each instead of 4 brushes carrying such a high current as in earlier case.
Also Slip rings needed to be insulated for voltage of 500V only. Thus we see that how it will be cheaper to have armature winding on stator.

2.     Low insulation levels required:-
As we have seen in both cases if we place armature winding on stator than slip rings needed to be insulated for lower voltages. Thus this type of construction will allow construction even upto 33KV synchronous machines
3.     Lower losses:-
When armature winding is placed on stator than we will require only 2 carbon brushes which means lower losses due to slip rings.
4.     Higher Output power:-
Since field winding of lighter weight is placed on field winding so this will leads to low centrifugal forces. So higher RPM of rotor will be possible and which will result into increased output for given dimensions.

5.     More rigid and easy construction:-
When armature winding is place on stator than it will be capable of handling higher voltages and currents , also it will be easier to place heavy winding on Stator slots. It will easier to install water tubing for cooling on stator than rotor. These all add to rigidness and convenience of synchronous machines.
6.     Higher Armature tooth Strength:-  
Higher current synchronous machines will require more armature copper for each slot.  For accommodating more copper by making slots deeper on armature.  It will be easier to cut deeper slots in when armature is on stator than on rotor. As if armature winding to be placed on rotor than rotor would have narrower and weaker teeth.
Stronger the teeth lower will be the noise and vibration.
7.     Lower rotor weight and lighter bearings:-
Field winding on rotor will leads to lower quantity of copper and insulation on rotor. This means lower weight of rotor and which means low priced bearings which means longer life due to minimum wear and tear.




Comments

Post a Comment

Popular posts from this blog

A2XWY; A2XFY Cables meaning; XLPE cables advantages over PVC cables

Technical Specification of Aluminum Cables in terms of codes So many times you have seen coding while specifying cables technical such as A2XWY now what does this means. Now there is nomenclature for the same which is used while describing the same. Where A -  Aluminium 2X- XLPE Insulation W – Steel round wire armour F- Steel Strip Armour WW- Double Steel round Armour FF- Double Steel Strip Armour Y- PVC outer Sheath Wa- Non Magnetic round wire Armour Fa- Non Magnetic Strip Armour AW- Aluminum Wire Armour Now As per A2XWY – This describes that it is Aluminum cable, XLPE insulated, With Steel round wire armour and having PVC outer Sheath. This coding is as per IS 7098(Part1):1988. You have also seen that there is coding for copper so there is no coding required in case of copper cables. XLPE cables advantages over PVC cables/ Thermoplastic cables:- 1.       XLPE cables have higher Power rating about 1.2 times PVC cables 2.       XLP...
Read more

Digital Multimeter working principle; DMM working

Image
Digital multimeters are most widely used in every industry as it used for measurement of Voltage, Current, Resistance, Capacitance and various other parameters. DMMs have been available for very several years. Yet it is still challenging to locate advice about how a digital multimeter works. The operation of a digital multimeter is comparatively uncomplicated, although there are obviously differences in how digital mulimeters work if they're from different makers.Despite this, there are several similarities and some general principles of how digital multimeters work. Fundamentals of how a DMM functions The key process occurring within a digital multimeter for any measurement is that of voltage measurement. All other measurements are derived from this basic measurement. So the best technique for understanding how a digital multimeter functions is in understanding this procedure. There are many kinds to digital converter, ADC. Nonetheless the one that is most widely used DMMs in di...
Read more

Wireless voltmeter using Arduino and RF 433MHz receiver and transmitter

Image
In this project i showed you how to make a wireless voltmeter using arduino and RF 433MHz receiver and transmitter. You can use this code and concept for many other projects, any project which used sensor with analog voltage output to sense temperature, gas leakage or light , etc. For example you can put a LM35 temperature sensor rather than potantiometer, you just have to putting its formula which convert LM35 output pin voltage to exact temperature. You also can make a wireless AC or DC power meter by doing some change in code and hardware (using hall effect current sensor and single phase voltage sensor). This type of RF module has distance range up to 200 meters according to datasheet but when i bought this RF module from Aliexpress its distance rang was very low, but i set its adjustable RF coil very carefully and i get very higher distance rang.(Don't play with RF coil if your module works good), You also have to use a 6 inch antenna to increase distance range to max as possi...
Read more