Please Log in or Register for more.

1 Answer

Answer :

In order that current should flow without causing excessive heating or voltage drop, the relay contacts should have low contact resistance, be clean and smooth, be of sufficient size and proper shape.

Like 0 like

Please log in or register to answer this question.

Related Questions



Last Answer : Overheating of relay contacts or contact born out is due to slow making and breaking of load circuit contacts, foreign matter on the contact surface, too low contact pressure.

Show More

150 views 1 answer







In the induction type directional over current relay, when a short-circuit occurs in the circuit (A) power flows in reverse direction (B) power flows in normal direction (C) directional power element does not operate (D) over current element is not energized
Last Answer : In the induction type directional over current relay, when a short-circuit occurs in the circuit power flows in reverse direction

Show More

123 views 1 answer








Last Answer : The under voltage relay can be used for generators, busbars, transformers, motors.

Show More

68 views 1 answer








Last Answer : The contacts of high voltage switches used in power system are submerged in oil. The main purpose of the oil is to extinguish the arc.

Show More

177 views 1 answer








Last Answer : The voltage appearing across the contacts after opening of the circuit breaker is called recovery voltage.

Show More

419 views 1 answer







what is the voltage drop as far as our distribution is concerned

Show More

6 views 0 answers







State the concept of internal voltage drop.
Last Answer : Concept of internal voltage drop: Every practical source offers some opposition to the current due to its internal parts or components. e.g. a 12V battery has electrodes made up of conducting ... internal voltage drop, the terminal voltage of practical voltage source is always less than its emf. 

Show More

243 views 1 answer







What is internal voltage drop and terminal voltage?
Last Answer : It is not permissible to just connect the positive terminal to the negative terminal of a cell with a copper wire. It will overheat and get damaged. This happens because the electromotive force (emf) ... than the nominal voltage (emf) of the cell and this lower voltage is called terminal voltage.

Show More

167 views 2 answers







To determine the polarity of the voltage drop across a resistor, it is necessary to know?
Last Answer : To determine the polarity of the voltage drop across a resistor, it is necessary to know direction of current through the resistor.

Show More

767 views 1 answer







In alternator where the voltage drop occurs?
Last Answer : In alternator voltage drop occurs in armature resistance, leakage reactance, and armature reactance.

Show More

139 views 1 answer







How do you fix voltage drop?

Show More

84 views 0 answers







In order that current should flow without causing excessive heating or voltage drop, the relay contacts should (a) have low contact resistance (b) be clean and smooth (c) be of sufficient size and proper shape (d) have all above properties
Last Answer : (d) have all above properties

Show More

10 views 1 answer







The frequencies and voltage used in Dielectric heating are (A) 10 – 30 MHz, upto 25 kV (B) 50 – 60 Hz, upto 25 kV (C) 10 – 30 MHz, upto 100 V (D) 50 – 60 Hz, 110 V – 230 V
Last Answer : The frequencies and voltage used in Dielectric heating are 10 – 30 MHz, upto 25 kV

Show More

118 views 1 answer







The purpose of the restraining coil in a biased differential relay is  (A) To reduce CT saturation during fault.  (B) To increase the sensitivity of the relay.  (C) To match the transformation ratio.  (D) To limit the spill current through the relay during heavy external fault.
Last Answer : d

Show More

706 views 2 answers







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

Show More

547 views 2 answers







A relay has a rating of 5 A, 2.2 sec IDMT and a relay setting of 125% TMS = 0.6. It is connected to a supply circuit through a C.T. 400/5 ratio. The fault current is 4000 A. The operating current of the relay is
Last Answer : A relay has a rating of 5 A, 2.2 sec IDMT and a relay setting of 125% TMS = 0.6. It is connected to a supply circuit through a C.T. 400/5 ratio. The fault current is 4000 A. The operating current of the relay is 6.25A

Show More

728 views 1 answer







The operating time of instantaneous relay is
Last Answer : The operating time of instantaneous relay is 0.1 sec

Show More

117 views 1 answer







What is the difference between relay and contactor?
Last Answer : Relay have smaller ratings. Contactor is a high rating relay.

Show More

5.1k views 1 answer







A negative sequence relay is used for protection of  (1) Generator (3) Motor (2) Transformer (4) Long Transmission lines
Last Answer : A negative sequence relay is used for protection of Generator 

Show More

627 views 1 answer







Buchholz relay is  (1) located in the conservator tank  (2) located in the transformer tank itself  (3) connected in the pipe connecting main tank of transformer and conservator  (4) installed in the circuit breaker
Last Answer : Buchholz relay is connected in the pipe connecting main tank of transformer and conservator 

Show More

117 views 1 answer







To prevent mal-operation of differentially connected relay while energizing a transformer, the relay restraining coil is based with  (1) second harmonic current  (2) third harmonic current  (3) fifth harmonic current  (4) seventh harmonic current
Last Answer : To prevent mal-operation of differentially connected relay while energizing a transformer, the relay restraining coil is based with  second harmonic current 

Show More

495 views 1 answer







Reactance relay is normally preferred for protection against
Last Answer : Reactance relay is normally preferred for protection against earth faults

Show More

120 views 1 answer







A solid state relay (A) withstands voltage transients (B) does not require auxiliary dc supply (C) provide low burden on CT and P (D) does not provide earth fault protection
Last Answer : A solid state relay provide low burden on CT and P

Show More

68 views 1 answer








Last Answer : The torque produced in induction type relay (shaded pole structure) is inversely proportional to the square of the current.

Show More

829 views 1 answer








Last Answer : Admittance relay is directional relay.

Show More

153 views 1 answer








Last Answer : The relay with inverse time characteristic will operate within 5 to 10 sec.

Show More

115 views 1 answer








Last Answer : Reactance relay is preferred for phase fault on short transmission line.

Show More

110 views 1 answer








Last Answer : Induction cup relay is operated due to changes in current, voltage, impedance.

Show More

352 views 1 answer








Last Answer : Interruption of large currents by relay requires arc suppressing blow out coils, wide separation of the opened contacts, high speed opening of contacts.

Show More

95 views 1 answer








Last Answer : A differential relay measures the vector difference between two or more similar electrical quantities.

Show More

159 views 1 answer








Last Answer : Burden of a protective relay is the power absorbed by the circuit of relay.

Show More

810 views 1 answer








Last Answer : The relay operating speed depends upon the spring tension, the rate of flux built up, armature core air gap.

Show More

270 views 1 answer







How do relay works ?
Last Answer : Relay working like contact it is noise less 

Show More

134 views 1 answer







What is the use of Buchholz relay in transformer?
Last Answer : This is a transformer that is used to step up and down current. 

Show More

152 views 1 answer







What is the difference between a switch and a relay?
Last Answer : Switch is simply a mechanical contact mechanism and relay is a electromagnetic switch . Switch can be direct mechanically turn on and off but relay can be operated by energising coil .

Show More

110 views 1 answer







Analyze the effect of supply voltage on performance of LED as regards current, Lumen output, efficacy and life. 
Last Answer : 1) Effect on Current:- In LED current depends upon supply voltage, if voltage get changes then current also change but this change in current will be control by resistors which are connected in series.  2) ...   4) Effect on Life:- If supply voltage is not stable then life of LED get reduced. 

Show More

106 views 1 answer







With the help of N-channel JFET describe the effect of input voltage VGS on output current ID.
Last Answer : Working of N channel FET: * When a voltage is applied between the drain and source with a DC supply (VDD), the electrons flows from source to drain through narrow channel ... where the channel gets completely blocked and the drain current becomes zero is called pinch- off voltage. 

Show More

229 views 1 answer







Define: i) Input Offset Voltage ii) Input offset Current iii) Input Bias Current iv) Output offset voltage
Last Answer : Definition of parameters of OPAMP is follows:  i) Input Offset Voltage: Input offset voltage is defined as the voltage that must be applied between the two input terminals of an OPAMP to null or ... to ground) and output voltage is obtained non zero such voltage is output offset voltage of opamp.

Show More

678 views 1 answer







A linear network has a current input 4cos(ω t + 20º)A and a voltage output 10 cos(ωt +110º) V. Determine the associated impedance.
Last Answer : Solution

Show More

158 views 1 answer







Source transformation voltage source to current source and vice versa

Show More

98 views 0 answers







What kills, current or voltage?
Last Answer : Current would kill. You can actually have thousands of bolts going through you and not even know it. Yes you probably know already voltage is current times resistance. Since your body is a resistor it would take just a small amount of current to create a very high voltage

Show More

149 views 3 answers







Why inductor current lags inductor voltage ?
Last Answer : Inductor is a wire wounding structure having a core material it induces emf which is opposite to the voltage supply and proportional to rate of change of current so current lags the voltage in inductor

Show More

112 views 1 answer







Explain lagging quantity and leading quantity, explain this concept with voltage and current waveform
Last Answer : When two alternating quantities attain their respective zero or peak values simultaneously, the quantities are said to be in-phase quantities. When the quantities do not attain their respective zero or ... current is leading the voltage or the voltage is said to be lagging behind the current.

Show More

140 views 1 answer







Define: 1) voltage ratio, 2) current ratio, 3) transformation ratio of transformer.
Last Answer : 1) Voltage ratio: The voltages in primary and secondary winding is proportional to number of turns in primary and secondary respectively. So, the voltage ratio is same as transformation ratio. V2/V1 = N2 ... as transformation ratio of transformer. It is denoted by K. K = N2/N1

Show More

2.7k views 1 answer







Write the relation between phase and line current, phase and line voltage for Star connection.
Last Answer : Line voltage is equal to root three times of phase voltage and line and phase currents are equal in star connection

Show More

375 views 2 answers







A zener voltage regulator has load requirements of 12 V and 2 A. The zener diode minimum current requirement is 0.2 A. The minimum voltage at input is 24 V. What is the required value of series resistance with source? A) 5.45 Ω B) 6 Ω C) 7.2 Ω D) 6.38 Ω  
Last Answer : A zener voltage regulator has load requirements of 12 V and 2 A. The zener diode minimum current requirement is 0.2 A. The minimum voltage at input is 24 V. What is the required value of series resistance with source? A) 5.45 Ω B) 6 Ω C) 7.2 Ω D) 6.38 Ω  

Show More

2.7k views 1 answer







Step-down transformer converts high voltage and low current into:  (A) How voltage and high current (B) High voltage and low current (C) Low voltage and high current (D) None of the above
Last Answer : Step-down transformer converts high voltage and low current into: Low voltage and high current

Show More

125 views 1 answer







Which of the following is the least expensive protection for over current in low voltage system?  (A) Rewireable fuse (B) Isolator (C) Oil Circuit breaker (D) Air break circuit breaker
Last Answer : Which of the following is the least expensive protection for over current in low voltage system?  (A) Rewireable fuse (B) Isolator (C) Oil Circuit breaker (D) Air break circuit breaker

Show More

260 views 1 answer







A current controlled voltage source is equivalent to :  (A) series voltage feed -back amplifier (B) shunt current feed -back amplifier (C) shunt voltage feed -back amplifier (D) series current feed -back amplifier
Last Answer : A current controlled voltage source is equivalent to : shunt voltage feed -back amplifier

Show More

119 views 1 answer







Which of the following theorems enables a number of voltage (or current) source to be combined directly into a single voltage (or current) source. (1) compensation theorem (2) reciprocity theorem (3) superposition theorem (4) Millman's theorem
Last Answer : Which of the following theorems enables a number of voltage (or current) source to be combined directly into a single voltage (or current) source. (1) compensation theorem (2) reciprocity theorem (3) superposition theorem (4) Millman's theorem

Show More

336 views 1 answer






Show More⇦ PreviousNext ⇨