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Answer :

Thermal overload relays are used to protect the motor against overcurrent due to heavy loads.

Related questions

Last Answer : Overload relays are of induction, solid state, thermal, electromagnetic type.

Description : IDMT relays are used to protect the transformer against :  (A) Internal short -circuits (B) Open circuits (C) External short circuits (D) Oil leakage

Last Answer : IDMT relays are used to protect the transformer against : External short circuits

Last Answer : The inverse definite mean time relays are used for over current and earth fault protection of transformer against internal short-circuits.

Last Answer : To protect most of the electrical equipment handling low power, the types of relays used are thermocouple, electronic and bimetallic.

Last Answer : A thermal protection switch can protect against overload.

Last Answer : The single phasing relays are used for the protection of three phase motors.

Last Answer : Impedance relays are used for phase faults on long line.

Last Answer : Discrimination between main and back up protection is provided by the use of relays which are slow.

Last Answer : Protective relays are devices that detect abnormal conditions in electrical circuits by measuring constantly the electrical quantities which differ during normal and abnormal conditions.

Last Answer : Directional relays are based on flow of power.

Description : D.C. shunt relays are made of?

Last Answer : D.C. shunt relays are made of many turns of thin wire.

Last Answer : Relays can be designed to respond to changes in resistance, reactance or impedance voltage and current, light intensity, temperature.

Description : Thermal overload relays are used to protect the motor against over current due to (a) short-circuits (b) heavy loads (c) grounds (d) all of the above

Last Answer : (b) heavy loads

Last Answer : Thermal circuit breaker has delayed trip action.

Description : How many types of types of relays are there?

Description : Consider the following statements. Which of these statements are correct ?  (1) Reactance relays are preferred for ground fault relaying  (2) Impedance relays are most suitable for:protecting long transmission lines  (3) Mho relays are best ... (1) and (3) (C) (2) and (4) (D) (1), (2) and (4)

Last Answer : Consider the following statements. Which of these statements are correct ?  (1) Reactance relays are preferred for ground fault relaying  (2) Impedance relays are most suitable for:protecting long transmission lines  (3) Mho relays are ... (1) and (3) (C) (2) and (4) (D) (1), (2) and (4)

Description : Explain the thermal triggering method of SCR. Enlist different triggering methods of SCR.

Last Answer : Types of Triggering: 1) Forward voltage triggering 2) Thermal triggering (Temperature triggering) 3) Radiation triggering (Light triggering) 4) dv/dt triggering 5) Gate triggering ... generated leakage current increases. This current gets multiplied internally and thyristor is turned on. 

Description : Define thermal runaway.

Last Answer : Thermal runaway  The problem with increasing temperature causing increasing collector current is that more current increase the power dissipated by the transistor which, in turn, increases its temperature ... self-reinforcing cycle is known as thermal runaway, which may destroy the transistor. 

Description : Classify condensers used in thermal power station. Explain each type in brief. 

Last Answer : Types of condenser: Classification: 1. Jet Condenser (Mixing Type) 2. Surface condenser (non Mixing type)  Explanation:-   1. Jet Condenser (Mixing Type) In Jet condenser the steam ... there in no direct contact between the steam and cooling water. This condensate is reused in boiler. 

Description : "Efficiency of thermal power station is low". — Justify. 

Last Answer : Justification: Efficiency of thermal power station is low":- Overall efficiency of T.P.P depends upon efficiency of boiler, turbine and alternator. The heat produced due to combustion of coal ... losses in thermal power plant is 71%, So efficiency of thermal power plant is less about 29% 

Description : State advantages of Pulverized coal w.r.t. thermal power plant. 

Last Answer : Advantages of Pulverized coal w.r.t. thermal power plant.  1. Due to pulvarization amount of fuel required to produce same amount of heat reduces. 2. Time required for combution reduces ... of air and thorough mixing of air and fuel, very high-combustion temperatures can be attained.

Description : State the function of super heater of a thermal power plant. 

Last Answer : Function of Super heater: -  Its function is to increase the temperature of steam by absorbing heat from exhausted hot flue gases.

Description : Describe thermal runaway of transistor and explain how it can be avoided.

Last Answer : Concept of thermal runaway:  1.We know that  IC = β IB + (1+ β) ICO  Where ICO is the leakage current and ICO is strongly dependent on temperature. 2. Leakage current approximately doubles for ...   Thermal runaway can be avoided by : 1) Using stabilization circuitry 2) Heat sink 

Description : State the function of cooling tower and condenser in thermal power station.

Last Answer : 1. Condenser:   Function of condenser is to convert exhaust steam again into water by reducing its temperature with the help of cold water. Also it reduces back pressure of steam turbine 2 ... tower : The function of cooling tower is to reduce the temperature of water coming from condenser.

Description : Write any four advantages and four disadvantages of thermal power plant.

Last Answer : .embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

Description : Explain ash disposal and dust collection in a thermal power plant.

Last Answer : Ash disposal:-  Various methods of disposal of ash are:  Mechanical handling system.  Pneumatic system. Hydraulic system  Steam jet system  Commonly used ash handling ... be done either manually or automatically.  This removed fly ash is collected in separate container

Description : State any four factors governing Selection of site for thermal power station. 

Last Answer : Following Factors are to be considered:- 1. It should locate near coal mine. 2. Sufficient quantity of water should be available. 3. Sufficient large space should be available. 4. It should be located ... laws of the land and the town planning. 14. The interests of national defense must be served.

Description : The overall efficiency of Thermal Power Plant is equal to _______________ .  (A) Regenerative Cycle Efficiency (B) Renkine Cycle Efficiency (C) Carnot cycle efficiency (D) None of the above

Last Answer : The overall efficiency of Thermal Power Plant is equal to Regenerative Cycle Efficiency. 

Description : In a thermal power plant, ash is collected in

Last Answer : In a thermal power plant, ash is collected in hoppers or bunkers

Description : The unit heat rate characteristic of a thermal power unit shows :  (A) Heat input per kWh of output versus the megawatt output of unit  (B) Heat input per kW of output versus the megawatt output ... hour output of unit  (D) Heat input per kW of output versus the megawatt hour output of unit

Last Answer : The unit heat rate characteristic of a thermal power unit shows : Heat input per kWh of output versus the megawatt output of unit 

Description : What is thermal runaway of a transistor?

Description : A thermal protection switch can protect against (a) short-circuit (b) temperature (c) overload (d) over voltage

Last Answer : (c) overload

Description : If overloading a DC machine becomes necessary in an emergency, you should ____________. A. cool the machine with portable blowers and fans B. hold thermal overload relays open with blocks of ... the windings for cooling D. increase the residual magnetism value of windings to reduce eddy currents

Last Answer : Answer: A

Description : Overload relays are of...... type. (a) induction (b) solid state (c) thermal (d) electromagnetic (e) all above

Last Answer : (e) all above

Description : When power is restored after a complete power failure, a steering gear pump motor will ____________. A. have to be restarted B. have to be reset C. restart automatically D. trip its overload relays

Last Answer : Answer: C

Description : Shading coils are installed on AC full-voltage starters to _____________. A. eliminate contact chatter B. dissipate opening contact arcs C. delay current build up in the holding coil D. protect the motor windings from momentary starting current overload

Last Answer : Answer: A

Description : A relay used for protection of motors against overload is :  (A) Impedance relay (B) Electromagnetic attraction type (C) Thermal relay (D) Buchholz's relay

Last Answer : D

Description : Define the following terms with respect to protective relays i) Relay time ii) Reset current iii) Plug setting multiplier and iv) Time setting multiplier

Last Answer : 1) Relay Time: The time interval between occurrence of fault and closure of relay contacts.  2) Reset Current: The value of current below which the relay resets and comes back to ... The adjustment arrangement provided for setting the operation time of relay is known as Time setting multiplier. 

Description : Protection against sustained overloads occurring in molded-case circuit breakers is provided by a/an __________. A. overvoltage release B. thermal acting trip C. thermal overload relay D. current overload relay

Last Answer : Answer: B

Description : What is the normal setting of overload relays?

Last Answer : Ask E/O. Normally 90-100% of rated normal current. Sometimes can be set to 105% of rated current.