anukul technique

What is the capacitor?

noreply@blogger.com (anukultechnique.blogspot. com) — Tue, 18 Sep 2018 18:39:00 +0000

The Capacitor.
A capacitor is formed when two conductors, usually of aluminium, are separated by an insulator sus as paper ect. For use in motors the strips are rolled together into a compact unit and placed into a sealed metal or plastic container. This may be either cylinderical or rectangular in shape and may be mounted on, in, or away from the motor. Two terminals or leads are provied for connection. The name capacitor is descriptive of the operation of the device. The capacitor acts essentially as a storage units that is,has capacity to store electricity and provides a leading current to the auxiliary or starting winding. All capacitors have this quality and all are electrically the same;they differ only in mechanical construction.
THE OIL-FILLED CAPACITOR
This capacitor is used mainly in the permanent-split capacitor motor and for the two-value capacitor motor. The capacitor use an oil-impregnated paper as the dielectric and are permanently connected in the circuit. They are capable of constant duty and are substantially larger than an equivalent microfarad value in a electrolytic type. Different manufactures use many types of oil or synthetic liquids as the impregnating medium. Capacities ranges from 2microfarads to 50 microfarads of their type.
THE ELECTROLYTIC CAPACITOR.
Electrolytic capacitors are used mainly in capacitor- start and two- value capacitor motor. This type consists of two sheets of aluminum foil neat are separated by one or more layers of gauge. The gauge has previously been saturated with a chemical solution called an electrolyte. The electrolyte forms a film which acts as the insulating medium of the electrolytic capacitor. These layers are rolled together and fitted into an aluminum or plastic container. In an electrolytic capacitor motor-starting electrolytic capacitor should not be kept in a circuit more than a few seconds at a time because they are designed for only intermittent duty.
CAPACITY
Capacitors are rated in microfarads. A capacitor for motor starting may have a capacity ranging from 2 to 800 microfarad or more,depending on its use,size and type. Capacitors may lose some capacity because of excessive use, overheating, or other conditions, in such a case it may be replaced with one of approximately the original value of capacity and voltage; otherwise the motor may not have the required starting torque.
When replacing a defective capacitor on a capacitor motor, be certain to use a replacement with a voltage rating at least as high as the original. Wherever any , question exists, it is always safter to use a capacitor of higher voltage rating.
There are three types of the capacitor motor and each employes capacitor in conjunction with the windings. These are capacitor- start motor, the permanent split capacitor more have a relatively high starting torque and use the electrolytic capacitor. The capacitor must not be used for continuous duty and must be switched out of the circuit when the motor attains a predetermined speed. The permanent split capacitor motor has relatively low starting torque and use an oil impregnated paper as the dielectric. These capacitor remain in the circuit at all time. The two-value capacitor motor has a high starting torque and uses the electrolytic and oil capacitor in parallel at start. When the motor reaches the required speed, the electrolytic capacitor is cut out of the circuit permitting the motor to operate as a permanent- split motor.

What is the reason of a motor runs with less than actual speeds?

noreply@blogger.com (anukultechnique.blogspot. com) — Thu, 13 Sep 2018 17:03:00 +0000

What is the reason of a motor runs with less than actual speed????
Tell the remedies also.
1. Short circuit inrunnig winding: The motor runs slow due to short critics in running winding coils. This motor jamps also. If this motor runs for a long time,it may burn. This fault may be determined by touching with hand or by internal growler. Its coils are to be rewound.
2. It may be possible that the starting winding is not cut off from the supply and the motor gives humming sound. For this,run the motor leaving the centrifugal switch out of circuit and taking starting winding leads out. If it is running O.K.then change the centrifugal switch or repair it,if possible by giving washer etc.
3. Reverse in running winding,.. It may be possible that the poles of running winding have been reversed when connection of a new winding are done. Check the polarity of poles by compass needle or screw drivers as stated above and correct if wrong.

4. Faulty capacitor. Mostly in capacitor motor the fault is due to capacitors. The best remedy is to change the capacitor by a new one. If the motor runs correctly, then the fault of capacitor is clear and if the motor dose not run properly there is some other fault.
5. Defective bearings... Due to defective bearings the motor runs with slow speed and abnormal sound. Due to small air gap between rotor and stator the rotor rubs with the stator and sound. bearing should be replaced.
6. Loose rotor bars.... The looseness of rotor basis known when motor takes less load and gives crowling sound. Check the rotor bars by taking out the rotor. Check them on growler also the loose rotor bar gives flickering in the lamp fitted on the growler. Move the rotor on the growler to locate defective bar and sloder the defective (I.e.loose) rotor bars.

Auto- transformer starter

noreply@blogger.com (anukultechnique.blogspot. com) — Sun, 11 Feb 2018 14:55:00 +0000

The starter of this type are used upto 25H.P. motors. This type of starter has autos transformer from which many tapping are taken out which give different voltages by which a big motor can be be supplied by low voltage. While in the in the star delta starter only 1/√3 times the full voltage can be given to the motor. The torque also varies with the voltage.
This starter also has overload relay, no volt coil and "OFF" switch.
In this starter the overload coil works on the magnetic effect I.e. when the current in the flows more than the normal, overload relay opens overload switch.

Star delta starter

noreply@blogger.com (anukultechnique.blogspot. com) — Thu, 08 Feb 2018 15:33:00 +0000

.This starter is fitted above 5H.P and upto 10H.P. in this starter there is two way switch which connects the 6ends of the motor once in star then in Delta. Like D.O.L.starter it also has overload relay ,no volt coil,current adjuster and "off" switch.
When we operate the handle down it is started, the ends A2,B2,C2,of the motor become short circuited and A1,B1, C1,get the supply. The motor becomes in star and gets 1/√3times or 58% of the full voltage by which the motor takes 1/3r current of that which the motor takes by starting in delta giving full voltage. It dropping of voltage in the line. By decreasing the current the torque of the motor also decreases to 1/3rd of the torque which it will give by direct star in deta. After taking 75% speed when the handle is done on delta, the ends,C1A2,A1B2,B1C2,are short circuited and each joint gets supply which connects the supply in delta and now since the motor is full speed the back e.m.f.is full. The motor is taking full current thereby giving the full torque.

Direct on line starter.

noreply@blogger.com (anukultechnique.blogspot. com) — Mon, 05 Feb 2018 15:42:00 +0000

Direct on line starter.
This starter gives the line voltage direct to the motor. It dose not reduce the voltage. This starter is used up to 5H.P. To connect the motor from the I.C.T.P. main switch or isolator is sufficient but the starter has the following advantage:-
(A) The motor can be made on and off quickly.
(B)It cuts the motor from the line on overloads.
(C) It prevents the motor from burning on single phase.
It has the following parts:
(1) Three straight strips which join the line direct to the motor. When "On" push is pressed these strips contact the lower strips.
(2) Forth strip works as interlock switch I.e when " On" posh is released after pressing,the 4th strip passes the current.
(3) Overload relay. This has thick wire like heater from which if more than normal current (in any one phase) flows then heating element becomes hot and the bimetallic strip placed inside it bends and it opens the overload switch which opens the circuit of no volt coil and all strips come to their original position and the motor stops.
(4)Their is one current adjuster on the upper side of bimetallic strips to set the current by which the starter may be adjusted on any current such as 2amps, 5amps etc.

Starting of three phase induction motors

noreply@blogger.com (anukultechnique.blogspot. com) — Sun, 04 Feb 2018 16:52:00 +0000

Starting of three phase motors.
When the motor is in standstill position and supply is given to it, the motor works like that transformer of which the secondary is short-cricuited. Thus the rotor (sec. of transformer) will take high current and thereby the stator will also take high current from the line. The following are the disadvantage of this high current:-
1.This may brunt the stator winding I.e. the installation may burst anywhere in the winding.
2.It may bring the supply voltage down and due to this the relays of other motor, running near to this motor,may trip (due to low voltage). This type of voltage drop is not allowed by supply company also. Therefore big H.P. motors are provided starters to minimise the starting current.
Motors up to 5 H.P.(A class motor upto7.5H.P.)may be connect direct to line.

TYPES OF STARTER
The following are the types of the starter:-
(A) Direct on line starter.
(B) Star Delta Starter.
(C) Auto star delta starter.
(D) Auto transformer type starter.
(E)Drum type or resistance type starter.

Induction Motor

noreply@blogger.com (anukultechnique.blogspot. com) — Sat, 03 Feb 2018 15:57:00 +0000

This motor is quite different from a D.C. motor because supply is not given to its rotor (armature) but the e.m.f. is induced in the rotor when stator is supplied which produces current in the rotor and the motor runs. Thus this motor is called induction motor. Nowadays for each work at each place A.C. single phase or 3phase motor is used.
The parts of this motor are as follows:-
1.Stator.
2.Rotor.
3.End cover.
4.Bearing.
5.Fan.

1.Stator: This is made of high silicon steel strips 0.3 to 1.35mm thick combining together which are called laminated strips and combination is called laminated core. The core has open or semi closed slots. In these slots winding is done. This core is fitted in a frame so that any external mechanical injury may not take place and rotor may rotet easily.
2.Rotor: It is also made of high Silicon steel strips 0.3 to 1.35 mm thick combining together. It has closed type slots in which winding is done. The winding is done with thick strips or rods. Nowadays melted aluminum is filled in these slots which work as winding. In big motor thick copper rods are inserted in the slots and end rings are connected (shorted) at the end of the rods by gas welding. This winding is called squirrel cage winding.
3.End cover: These are made of cast iron and keep the rotor exact in the centre of this stator so that the rotor may move easily. These are fitted with blots with the stator frame. The frame also is made of cast iron.
4.Bearing: Mostly in 3 phase motors ball bearings are used and small single phase motor bush bearings are used. Their working is to give the rotor free rotation in the stator.
5.Fan: In motor, its working is to cool the motor. Mostly these are made of cast iron and fitted on the rotor shaft. When the motor runs on load, the heat is produced in the motor due to losses. If this heat is not transferred out, the winding will be brunt. The fan serves the purpose of transferring heat from inside to outside of the motor. It sucks the cold air from the atmosphere. This air comes inside the motor through holes and goes out after cooling the winding of the motor. In many motors this fan is fitted on the rotor near to the winding and in many motors it is fitted outside the cover I.e. after fitting the cover and then a M.S.sheet or cast iron. Fan,cover is fitted which cover this fan.

The stator of the capacitor motor and windings done in it.

noreply@blogger.com (anukultechnique.blogspot. com) — Wed, 31 Jan 2018 16:09:00 +0000

The stator of this motor is made of laminated silicon steel the slots of which are semiclosed. This core is placed in a steel or mild steel frame.
In its slots two windings are done from an insulated copper wire,which are called running and starting winding. When the motor is started, both the windings are connected with the line when the motor is speeds up to 75%of the full speed, the starting winding is cut off by centrifugal switch automatically and only running winding work.

Capacitor motor.

noreply@blogger.com (anukultechnique.blogspot. com) — Wed, 24 Jan 2018 14:20:00 +0000

Capacitor motors are used only on A.C. single phase supply. Such motors are
used for refrigerators, compressure, cloth washing machines, printing press, drill machines, lathe machines, water pumps and fans etc.

Parts of capacitor motor:

There are 5 main parts of this motor.

1. Moving part -rotor.

2.Static part- stator.

3.End shields or end covers which is fitted with stator with nut and blots.

4.Centrifugal switch which is fitted inside the motor.

5.Capacitor which is connected in series with the starting winding. Capacitor is mostly fitted with the motor on the top or at one side.