With a neat sketch, explain the working of Thermal relay.

1 Answer

Answer :

Working of Thermal Relay:

image

1) When the system is in normal operating condition, the heating element carries normal current from CT, this current produces heat = I2Rt. This heat is not sufficient to bent bimetallic strip hence relay contact remain open. 2) The insulated liver arm is connected to the trip coil along with the spring and the bimetallic strips. The tension of the spring is varied by the help of the sector-shaped plate 3) When the fault occurs on the system, the heating element carries abnormal current supplied by the CT, hence developing more heat which bents bimetallic strip, the tension of the spring releases which operates relay contacts resulting into providing trip signal to trip circuit.

Related questions

Description : Describe the operation of current differential relay with neat sketch.

Last Answer : Operation of Current Differential Relay: Figure shows an arrangement of an overcurrent relay connected to operate as a differential relay for alternator protection under fault conditon. ... current flows through relay coil, causing relay to operate for protection of alternator winding.

Description : Explain working of ELCB with neat sketch diagram.

Last Answer : Earth Leakage Circuit Breaker(ELCB): Earth leakage circuit breaker is a safety device used in electrical installations with high earth impedance to prevent shocks and disconnect power under earth fault ... tripping in domestic installations with tripping time being as low as 25 msec.

Description : With the help of neat diagram, explain operation of static relay.

Last Answer : Operation of Static Relay: Operation: 1) The solid-state component used are transistors, diodes, resistors, IC s, capacitor etc. The function of comparison and measurement are accomplished by ... ) An auxiliary dc supply is provided for operation of static relay elements as shown in figure.

Description : Explain Buchholz relay with neat labelled diagram.

Last Answer : Buchholz relay: The relay is located in the path of the oil from transformer tank to conservator. As seen from diagram, the upper mercury switch operates the alarm circuit due to tilting of the ... manner that it senses the sudden violent movement of oil from transformer tank to conservator.

Description : Explain with neat sketch, the Pilot wire protection scheme applied to transmission line.

Last Answer : Pilot Wire Protection scheme of Transmission Line : Figure shows the single line diagram of Merz price voltage balance system for pilot wire protection of three phase transmission line. ... through the relay, which gives trip signal to the circuit breaker for protection of transmission line.

Description : Explain differential protection scheme for busbars with neat sketch.

Last Answer : Differential Protection Scheme for Bus bar:  Under normal conditions, the sum of the currents entering the bus bar zone is equal to those leaving it and no current flows through the relay ... of these currents will flow through the relay coil causing opening of circuit breaker of bus-bar.

Description : Explain single phasing preventer with neat sketch diagram.

Last Answer : Single phasing preventer: Single phasing preventers are generally used for small / medium capacity motors. Single phasing preventers are connected in secondaries of line CTs. These mainly contains ... command is given to circuit breaker or starter. Thus it protects motor from damage.

Description : Explain distance protection of transmission line with neat sketch diagram.

Last Answer : Distance protection of Transmission line: Distance protection scheme uses impedance relay. The relay operation is based on the impedance (or distance) between the relay and point of fault. Figure shows ... than ZL and impedance relay operates which operates the CB and line is protected.

Description : Explain Horn-gap lightning arrester with neat sketch diagram.

Last Answer : Horn Gap Type Lightning Arrester: It consists of two horn shaped metal rods A and B separated by a small air gap. The horns are so connected that distance between them gradually increases towards the ... being hot, moves up naturally along the horns. So it is elongated and naturally quenched.

Description : Describe the construction and Operation of Buchholz relay with neat labeled diagram.

Last Answer : Construction of Buchholz Relay: It takes the form of a domed vessel placed in the connecting pipe between the main tank and the conservator. The device has two elements. The upper element ... manner that it senses the sudden violent movement of oil/gas from transformer tank to conservator. 

Description : Draw a neat sketch of earth fault protection of auxiliary circuit of electric loco. State the function of relay and isolating resistance.

Last Answer : Ans: Earth fault protection for auxiliaries in Loco: Function of relay: The earth fault occurring anywhere in the auxiliary circuit gets monitored by the relay which acts to trip the main CB. Function of ... star point to earth through a high resistance so that the relay operation is avoided.

Description : Explain the working of single phasing preventer with neat diagram.

Last Answer : Working of single phasing preventer:  Single phasing preventers are generally used for small / medium capacity motors. Single phasing preventers are connected in secondary of line CTs. These ... contact gets opened which stops the motor to avoid further damage when single phasing occurs. 

Description : Explain working of surge absorber with neat diagram.

Last Answer : Surge Absorber: Voltage transients or surges on the power system may originate from switching or lightning. These surges set up traveling waves in the transmission lines. These traveling waves may reach ... heat due to transformer action. Generally, it is used for the protection of transformers.

Description : Describe the working of HRC fuse with neat diagram.

Last Answer : Working of HRC Fuse: Under normal conditions, the fuse element is at a temperature below its melting point. Therefore, it carries the normal current without overheating. When a fault ... powder and results in the formation of high resistance substance that helps in quenching the arc. 

Description : Explain with a neat sketch the working of the apparatus used for distillation on laboratory scale. 

Last Answer : There are two apparatus used for distillation on laboratory scale. 1. Simple apparatus. 2. Still apparatus. Simple apparatus: Working: 1. Water is filled in the round bottom flask. ... level device is fitted in such a way that only heated water free from gases enters the boiler. 

Description : Explain working of Gobar Gas plant with a neat sketch.

Last Answer : It is a type of composting plant. In this plant gobar gas is produced from solid waste which is biodegradable in nature. A mixture of gases is produced by breakdown of organic matter in the absence of ... Dioxide. It is used as a fuel and the digested sludge is used as fertilizer for crops

Description : State and explain the working principle of hydrodynamic spring with neat sketch.

Last Answer : Working principle: Hydrodynamic springs are comparatively small, thick walled cylinder in which the spring effect is produced by applying load to the fluid in the cylinder through a small ... These springs are particularly useful in applications requiring high load capacities and stiffness.  

Description : Explain the working of Ackerman steering gear mechanism with neat sketch.

Last Answer : Working: The whole mechanism of Ackerman Steering gear is on the back of the front wheels. The Ackerman steering gear consists of turning pairs The slotted links AM and BH are attached ... each end. The steering is affected by moving CD to the right or left of its nominal position. 

Description : Draw the neat sketch of overhead valve operating mechanism and explain its working.

Last Answer : Overhead valve mechanism: Figure shows the valve mechanism to operate the valve when it is in the cylinder head (in I and F head design). This type of mechanism requires two additional moving parts the push ... close. A spring (attached to the valve) returns the valve to its seated position.   

Description : Explain working of over head valve mechanism with neat sketch.

Last Answer : Overhead valve mechanism: Figure shows the valve mechanism to operate the valve when it is in the cylinder head (in I and F head design). This type of mechanism requires two additional moving parts the ... to close. A spring (attached to the valve) returns the valve to its seated position.  

Description : Draw a neat lebelled sketch of optical square. Explain its working.

Last Answer : Working of optical square1. Optical square works on principle of optical square to set perpendicular offset 2. Keep ranging rods at point B and C as shown in fig. 3. Observe the ... matched each other point D can be marked on ground and distance CD is measured as perpendicular offset.

Description : Draw a neat sketch of optical square. Explain its working.

Last Answer : Optical Square: Working: The optical square consists of circular box 50 mm in diameter, 12.5 mm in depth. The box has three slits as A,B, and C. bb' is horizon glass, half silvered i.e ... the point on the chain line where the offset can be dropped to meet point J as shown in fig.  

Description : Explain the working of diesel engine glow plugs with neat sketch

Last Answer : Glow plug is an aid for cold starting of a C.I. engine. The self-ignition temperature of diesel is 250°C. For compression ignition, the charge (air + diesel) should reach a temperature of ... plugs is automatically interrupted. But starting may be attempted again as soon as the driver wishes.   

Description : With the help of constructional diagram, explain the working of LDR with neat sketch.

Last Answer : Working Principle The resistance depends on the intensity of light, as resistance decreases with increase in light intensity. Characteristics Applications of LDR 1. They are often ... circuits, light intensity meters, for counting the packages moving on a conveyor belt, etc.

Description : Explain the working principal of EDM with a neat sketch. 

Last Answer : Let the distance between P and Q be D' which is to be measured. A wave is transmitted from the transmitter at station P' with certain phase angle. . There ... finding the distance, the phase difference between transmitted wave and reflected wave is measured and converted into distance.

Description : With neat sketch explain the working principle of CNC machines. 

Last Answer : Working Principle of CNC machine:- A CNC machine also has a tape reader or any other input media for entry of the part program. CNC uses the part program in a different manner though there is ... to the reference. These two signals are compared and necessary action is controlled.   Or  

Description : Explain the working principle of resistance welding with neat sketch. 

Last Answer : Resistance Welding Process: 1.Resistance Spot welding:  Spot welding is employed to join overlapping strips, sheets or plates of metal at small areas. The pieces are assembled between two ... welding small parts. Butt Welding provides joining with no loss of the welded materials.  

Description : Explain the working principle of MIG welding with neat sketch.

Last Answer : MIG Welding: Gas-metal-arc welding is a gas shielded metal arc welding process which uses the high heat of an electric arc between a continuously fed, consumable electrode wire and the material to be ... will not combine with metal. Carbon dioxide is most commonly used as it inexpensive.

Description : Explain construction and working of Combination Die with neat sketch.

Last Answer : Combination Die: In this both cutting and non-cutting operations are performed at one station of the press in every stroke of the ram. Figure shows a combination of blanking and drawing die.In this ... as blank holder when the drawing punch descends and draws the blank into the desired shape.

Description : Explain in detail principle, construction and working of Radiation Pyrometer with neat sketch.

Last Answer : Radiation pyrometer Principle: According to Stefan Boltzmann's law, the intensity of radiant energy emitted by a hot target varies as the fourth power of its absolute temperature. ... is calibrated in terms of target temperature by using either a voltmeter or Wheatstone bridge circuit.

Description : Explain construction and working of Bimetallic Thermometer with neat sketch.

Last Answer : Bimetallic thermometer: Diagram Construction and working: Bimetallic strip consists of two strips of metal such as invar and brass welded together, each strip made from a metal having a ... The movement of the bimetallic strip is utilized to deflect a pointer over a calibrated scale. 

Description : Draw neat sketch of Rotameter and explain its working principle.

Last Answer : Rotameter: - A variable-area flowmeter is one where the fluid must pass through a restriction whose area increases with flow rate. The height of the float is directly proportional to the flowrate ... on glass tube and the flow rate can be determined by direct observation of the metering tube  

Description : Explain Construction and working of Francis Turbine with neat sketch.

Last Answer : The main parts of the Francis turbine are: 1) Penstock: It is the large pipe which conveys water from the upstream of the reservoir to the turbine runner. 2) Spiral casing: It is a closed passage ... After doing the work the water is discharge to the trail race through the draft tubes.

Description : Explain the construction and working of induced draft cooling tower with neat sketch.

Last Answer : Induced draft cooling tower :  Diagram: Construction and working: Cooling towers are employed to cool utility cooling water by direct contact with air. The parts of a cooling tower are ... top pulls the hot air through the fills and cooled water gets collected in the cold water basin.

Description : Explain working of water level indicator with neat sketch.

Last Answer : Water level indicator: Working: Its function to indicate water level in boiler. usually two water level indicator are fitted to in front of boiler. WLI shows the water level in in the boiler drum ... goes below a fixed mark , so that corrosive action may be taken in time to avoid accident. 

Description : With neat sketch explain the construction and working of heat exchanger used for handling corrosive liquid.

Last Answer : Graphite block heat exchanger:   Graphite heat exchangers are well suited for handling corrosive fluids. Graphite is inert towards most corrosive fluids and has very high thermal conductivity. Graphite being ... vertical faces direct the service fluid through the exchanger in a cross flow.

Description : Explain principle of working of Impulse steam turbine with neat sketch.

Last Answer : Construction: Impulse turbine is simpler, less expensive and does not need to be pressure proof. It can operate with any pressure stream but is considerably less efficient. Impulse turbine consist of one ... by one set of moving blade ring as shown in Fig. for a single stage impulse turbine.

Description : Explain with neat sketch working of centrifugal pump.

Last Answer : Working of centrifugal pump is in three stages i. Priming ii. Starting iii stoping i. Priming- The operation of filling the casing, impeller and suction pipe upto delivery valve ... pump, delivery valve should be closed partly. Motor is switched off and then value is closed fully. 

Description : Explain with a neat sketch the working of Bourdon’s pressure guage.

Last Answer : Working: Bourdon tube pressure gauge is used to measure high pressure. It consists of tube as shown in fig. having elliptical cross section. This tube is called as Bourdons Tube. ... pressure in the case containing the bourdon tube is usually atmospheric, the pointer indicates gauge pressure.

Description : Explain the working of Scotch Yoke mechanism with neat sketch.

Last Answer : Scotch yoke mechanism. This mechanism is used for converting rotary motion into a reciprocating motion. The inversion is obtained by fixing either the link 1 or link 3. In Fig. link 1 is fixed. In this ... link 4 (which corresponds to a frame) reciprocates. The fixed link 1 guides the frame

Description : Draw a neat sketch of ‘Locomotive coupler’ mechanism. Explain its working in brief.

Last Answer : Figure: Coupler Rod of Locomotive  (Link AD = Link BC = Crank Link CD = Coupling Rod Link AB = Fixed Link = Frame) Working of Coupler Rod of Locomotive: It is an ... center distance between them. This mechanism is meant for transmitting rotary motion from one wheel to the other wheel.

Description : Explain the working of Lamont boiler with neat sketch.

Last Answer : 1. This is a modern high pressure, water tube boiler working on a forced circulation. 2. The circulation is maintained by a centrifugal pump, driven by a steam turbine, using steam from the ... application. Lamont boilers generates 45 to 50 tones steam per hour at 130 bar with 5000 C.

Description : Explain with neat sketch the construction and working principle of megger.

Last Answer : Megger: Construction of Megger : Two coils: the current coil and pressure coil are mounted at an angle on the same spindle and form the part of the moving system. These coils are ... force produces a torque that is used to deflect the pointer of the device which gives some reading.

Description : Explain with neat sketch; the construction and working principle of Repulsion type moving iron instrument.

Last Answer : Repulsion Type Moving Iron Instrument: Construction: It consist of fixed cylinder hollow coil which carries operating current inside the coil there are two soft iron pieces. One of which is ... magnetized with same polarity a repulsive force act on them and moving iron piece gets deflected. 

Description : Explain with neat sketch, the working of full wave rectifier voltmeter.

Last Answer : Full Wave Rectifier Type Voltmeter: Working of full wave rectifier type A. C. Voltmeter Referring to the circuit diagram, for rectification, a full wave bridge circuit (ABCD) is used. Input ... current passing through meter is given as, which causes full scale deflection of the meter.

Description : Explain with neat sketch working of direct drive SWT. Give any two advantages of it over geared type SWT.

Last Answer : Direct Drive SWT: This plant has no gear box. Turbine blades are very light weight made up of stiff carbon fibre material. Blades are flat shaped. Due to this shape, lift increases. ... needed is less 4. More reliable 5. Better performance 6. Light weight 7. Less maintenance

Description : Explain with neat sketch the working principle of MIG.

Last Answer : In metal-arc inert gas welding the Weld area is shielded by an effectively inert atmosphere of argon, helium, carbon dioxide, or various other gas mixtures . The consumable bare Wire is fed automatically ... of the molten-weld puddle. Multiple-weld layers can be deposited at the joint. 

Description : Explain working principle of stroboscope with neat sketch.

Last Answer : Diagram : Explanation : The arrangement of two flanges A and B placed at a distance on the shaft is as shown. Flange A carries a scale while flange a pointer. When a torque ... measuring the angular twist. This method is simple and inexpensive. However, the accuracy of measurement is poor.

Description : With neat sketch explain working of Weston type synchroscope.

Last Answer : Weston type synchroscope:  Working: It consists of three limbed transformer. The winding on one of the outer limbs is excited from bus- bars and that on other limb by incoming machine. The two fluxes ... the lamp is flickering at a very much slow rate and it is at its maximum brightness.

Description : With a neat sketch explain working of 1 phase dynamometer type power factor meter.

Last Answer : Working of 1 phase dynamometer type power factor meter : The current coil is connected in series with load. Two pressure coils marked as A and B are connected across the supply terminals ... becomes stationary and the pointer shows steady deflection corresponding to the power factor of the load.