State the function of a contactor in a power circuit of locomotive. List different types of it and state one application of each.

State the function of a contactor in a power circuit of locomotive. List different types of it and state one application of each.
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Ans: Contactor in power circuit of locomotive is used to connect relevant sections for operation. Connecting or disconnecting the power circuit at different conditions of operation and at different locations. 

They are classified by their methods of closing the movable contact – 1) electromagnetic 2) electro -pneumatic 3) cam & roller operated 

Application : 1) Electromagnetic – used in the circuits carrying low currents such as taken by auxiliary motors. 2) Electro pneumatic – used to control heavy power currents. 3) Cam & roller operated – used for group switching.

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Description : The winch shown in the illustration will not operate in any speed in the lowering direction and at an abnormal speed in 'first point hoist'. The possible cause is that _______________. EL-0102 A. ... '1M' in the power circuit are badly corroded D. master switch contacts 'MS6' have weak springs

Last Answer : Answer: B

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Description : The winch shown in the illustration operates in any of the positions with the master switch in the 'lower' direction, but will not 'hoist' in any of the master switch hoist positions. Which of the listed faults ... '2M' in the power circuit may be badly corroded. D. Series relay 'FR' may be open.

Last Answer : Answer: A

The heaters for the winch circuit shown in the illustration are powered from _____________. EL-0102 A. a separate source B. the winch main bus C. the master switch power circuit D. the contactor control circuit

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Last Answer : Answer: D

A circuit is protected from overheating by a/an ___________. A. pyrometer B. thermal overload relay C. magnetic contactor D. overload transformer

Description : A circuit is protected from overheating by a/an ___________. A. pyrometer B. thermal overload relay C. magnetic contactor D. overload transformer

Last Answer : Answer: B

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Description : Can we use AC contactor in DC circuit?  

Last Answer : Yes, but with adequate de-rating.  

Match the following: List-I List-II A. Varanasi I. Indian Rare Earths Ltd B. Koyali II. Hindustan Machine Tools Ltd C. Pinjore III. Diesel Locomotive Works D. Alwaye IV. Petro-Chemical Complex Codes: A B C D (a) I II III IV (b) IV III II I (c) III IV II I (d) III IV I II

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Last Answer : Ans: (c)

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List any four types of resistors. Give one application of each.

Description : List any four types of resistors. Give one application of each.

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Explain the need of maintenance of electric locomotive.

Description : Explain the need of maintenance of electric locomotive. 

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A train locomotive whose mass is 1 x 106 kilograms is traveling EAST at a speed of 100 kilometers per hour. A NORTHERLY wind is applying a force of 100 Newtons on the locomotive. How much work is the wind doing on the locomotive for each 10 meters it travels? w) 0 joules x) 1,000 joules y) 10,000 joules z) 100,000 joules

Description : A train locomotive whose mass is 1 x 106 kilograms is traveling EAST at a speed of 100 kilometers per hour. A NORTHERLY wind is applying a force of 100 Newtons on the locomotive. How much work is the wind doing ... 10 meters it travels? w) 0 joules x) 1,000 joules y) 10,000 joules z) 100,000 joules

Last Answer : ANSWER: W -- 0 JOULES

The power of a locomotive is 315 kW and the total weight of the train is 2000 kN. If the track resistance is 15 N per kN, the maximum speed that the locomotive can attain on level track will be a.43 kmph b.83 kmph c.103 kmph d.107 dynes e.38 kmph

Description : The power of a locomotive is 315 kW and the total weight of the train is 2000 kN. If the track resistance is 15 N per kN, the maximum speed that the locomotive can attain on level track will be a.43 kmph b.83 kmph c.103 kmph d.107 dynes e.38 kmph

Last Answer : e. 38 kmph

The power of a locomotive is 315 kW and the total weight of the train is 2000 kN. If the track resistance is qN per kN, the maximum speed that the locomotive can attain on level track will be a.103 kmph b.83 kmph c.107 dynes d.43 kmph e.63 kmph

Description : The power of a locomotive is 315 kW and the total weight of the train is 2000 kN. If the track resistance is qN per kN, the maximum speed that the locomotive can attain on level track will be a.103 kmph b.83 kmph c.107 dynes d.43 kmph e.63 kmph

Last Answer : e. 63 kmph

In a steam locomotive electric power is provided through?

Last Answer : In a steam locomotive electric power is provided through small turbo-generator.

State the classification of locomotive.

Description : State the classification of locomotive.

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List different types of stepper motor. State one application of stepper motor.

Description : List different types of stepper motor. State one application of stepper motor.

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In the illustration shown, coil 'MR' is a ____________. EL-0012 A. running contactor coil B. rupture (blowout) coil C. resistance coil D. reversing coil

Description : In the illustration shown, coil 'MR' is a ____________. EL-0012 A. running contactor coil B. rupture (blowout) coil C. resistance coil D. reversing coil

Last Answer : Answer: A

Which component is responsible for energizing solenoid 'B1-B2' and releasing the brake for the winch motor shown in the illustration? EL-0102 A. Contactor '3M' B. A spring not shown in the schematic diagram C. Resistor 'B2-R1' D. Relay 'FR-B.O.'

Description : Which component is responsible for energizing solenoid 'B1-B2' and releasing the brake for the winch motor shown in the illustration? EL-0102 A. Contactor '3M' B. A spring not shown in the schematic diagram C. Resistor 'B2-R1' D. Relay 'FR-B.O.'

Last Answer : Answer: A

The illustrated motor fails to start and gives a loud hum when the start button is depressed, your first action should be to __________. EL-0007 A. disassemble the motor to fix the centrifical switch so the start windings will be energized B. push the stop button to deenergize the 'M' coil C. reset the thermal overload D. hold the 'M' contactor closed by hand while wearing electrical safety gloves to get motor started

Description : The illustrated motor fails to start and gives a loud hum when the start button is depressed, your first action should be to __________. EL-0007 A. disassemble the motor to fix the centrifical ... D. hold the 'M' contactor closed by hand while wearing electrical safety gloves to get motor started

Last Answer : Answer: B

If many turns of an alternating current coil for a contactor become short circuited, the coil _____________. A. will continue to operate B. will probably burn out immediately C. will operate on reduced current D. temperature will drop

Description : If many turns of an alternating current coil for a contactor become short circuited, the coil _____________. A. will continue to operate B. will probably burn out immediately C. will operate on reduced current D. temperature will drop

Last Answer : Answer: B

When troubleshooting motor controllers, a shorted relay or contactor coil is often indicated by _______________. A. a resistance reading of 'infinity' on an ohmmeter B. charred insulation and/or a blown control fuse C. a reading of 'zero' on a megger from one of the coil's leads to ground D. a higher-than-normal voltage reading across the winding

Description : When troubleshooting motor controllers, a shorted relay or contactor coil is often indicated by _______________. A. a resistance reading of 'infinity' on an ohmmeter B. charred insulation and/or a blown ... of the coil's leads to ground D. a higher-than-normal voltage reading across the winding

Last Answer : Answer: B

If a magnetic controller contactor fails to pick up when the coil voltage is applied to the contactor coil, the cause may be _____________. A. overload B. misalignment of the affected contactor contacts C. low spring pressure D. an open contactor coil

Description : If a magnetic controller contactor fails to pick up when the coil voltage is applied to the contactor coil, the cause may be _____________. A. overload B. misalignment of the affected contactor contacts C. low spring pressure D. an open contactor coil

Last Answer : Answer: D

If many turns of an alternating current coil for a contactor become short circuited, the coil _____________. A. temperature will drop B. will probably burn out immediately C. will continue to operate D. will operate on reduced current

Description : If many turns of an alternating current coil for a contactor become short circuited, the coil _____________. A. temperature will drop B. will probably burn out immediately C. will continue to operate D. will operate on reduced current

Last Answer : Answer: B

Magnet chatter or 'pumping' occurring in a magnetic contactor can be caused by ______________. A. dirt or grease on pole faces B. mechanical interference in the contacts C. chattering contacts on the control relay D. magnetic lock out of the contacts

Description : Magnet chatter or 'pumping' occurring in a magnetic contactor can be caused by ______________. A. dirt or grease on pole faces B. mechanical interference in the contacts C. chattering contacts on the control relay D. magnetic lock out of the contacts

Last Answer : Answer: C

During its operation, loud buzzing and resultant welding of contacts of a magnetic relay may be caused by __________. A. overheating of the contactor coil B. low voltage on the operating coil C. low insulation resistance to ground D. lubrication of the contact bearing points

Description : During its operation, loud buzzing and resultant welding of contacts of a magnetic relay may be caused by __________. A. overheating of the contactor coil B. low voltage on the operating coil C. low insulation resistance to ground D. lubrication of the contact bearing points

Last Answer : Answer: B

A shading coil used in an AC magnetic controller, functions to _____________. A. reduce vibration and noise in the contactor B. prevent flux buildup in the operating coil C. eliminate arcing when the contacts close D. energize the operating coil and 'pull in' the contacts

Description : A shading coil used in an AC magnetic controller, functions to _____________. A. reduce vibration and noise in the contactor B. prevent flux buildup in the operating coil C. eliminate arcing when the contacts close D. energize the operating coil and 'pull in' the contacts

Last Answer : Answer: A

Which of the following statements represents the main difference between a relay and a contactor? A. Contactors control current and relays control voltage. B. A relay is series connected and a contactor is parallel connected. C. Contactors can handle heavier loads than relays. D. Contactors are made from silver and relays are made from copper.

Description : Which of the following statements represents the main difference between a relay and a contactor? A. Contactors control current and relays control voltage. B. A relay is series connected and a contactor ... loads than relays. D. Contactors are made from silver and relays are made from copper.

Last Answer : Answer: C

Radioactive nuclear waste is treated in (A) Mixer-settler extractor (B) Rotating-disc contactor (C) Pulsed column extractor (D) Bollman extractor

Description : Radioactive nuclear waste is treated in (A) Mixer-settler extractor (B) Rotating-disc contactor (C) Pulsed column extractor (D) Bollman extractor

Last Answer : (C) Pulsed column extractor

The interfacial area per unit volume of dispersion, in a gas-liquid contactor, for fractional hold up of gas = 0.1 and gas bubble diameter = 0.5 mm is given by (in m2 /m3 ) (A) 500 (B) 1200 (C) 900 (D) 800

Description : The interfacial area per unit volume of dispersion, in a gas-liquid contactor, for fractional hold up of gas = 0.1 and gas bubble diameter = 0.5 mm is given by (in m2 /m3 ) (A) 500 (B) 1200 (C) 900 (D) 800

Last Answer : (A) 500

What is the safety reason to keep the contactor / MCC remote from motor?

Description : What is the safety reason to keep the contactor / MCC remote from motor?  

Last Answer : Contactor = sparking equipment. Not suiting for hazardous location.  

Can we file the pitted contacts of contactor?

Description : Can we file the pitted contacts of contactor?

Last Answer : No, use emery paper and etc.  

What material used for contactor?

Description : What material used for contactor?

Last Answer : Silver-nickel for

Why pure silver is not used in contactor?

Description : Why pure silver is not used in contactor? 

Last Answer : Affected by sulphur, mechanical or arcing damages (adv. Lower voltage drop) 

Why copper contact are not used in contactor?

Description : Why copper contact are not used in contactor? 

Last Answer : Because corrosion rate increases. Poor surface property , large closing force required. 

Why shading rings provided in armature core of ac contactor. Why not for dc contactor?

Description : Why shading rings provided in armature core of ac contactor. Why not for dc contactor? 

Last Answer : Because the force developed is not steady in ac therefore contacts will chatter but if shading ring is used force developed becomes steady due to splitting of phases of flux, therefore contacts becomes bounce free and humming sound reduces.  

What is the difference between isolator and contactor?

Description : What is the difference between isolator and contactor?

Last Answer : Contactor is used for on load operation. Because they are fast acting devices. They posses arc chamber and arc chutes. Arc chamber and arc chute make it easy to extinguish the arc produced during on ... acting devices. The arc time is more in slow acting devices and operated only in off load. 

What is the difference between a contactor and a breaker?

Description : What is the difference between a contactor and a breaker?

Last Answer : Contactor is not designed to open on short circuit condition (fuse will take care of this situation). Breaker is having complicated mechanism for closing and tripping. 

DC relay coil or contactor coils must be connected to which side?

Description : DC relay coil or contactor coils must be connected to which side?

Last Answer : Negative side of the DC supply to avoid galvanic effect on the coil, which will corrode the coil.  

What is a magnetic contactor? Where is it used?

Description : What is a magnetic contactor? Where is it used?

Last Answer : A contactor is an electrically controlled switch used for switching a power circuit, similar to a relay except with higher current ratings. Contactors are used to control electric motors, lighting, heating, capacitor banks, and other electrical loads.

What is the difference between relay and contactor?

Description : What is the difference between relay and contactor?

Last Answer : Relay have smaller ratings. Contactor is a high rating relay.

Time constant of a circuit is the time in seconds taken after the application of voltage to each?

Description : Time constant of a circuit is the time in seconds taken after the application of voltage to each?

Last Answer : Time constant of a circuit is the time in seconds taken after the application of voltage to each 63% of maximum value.