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Why is it necessary to insert resistance in series with the motor armature when starting a dc motor?
Inserting resistance in series with the motor armature when starting a DC motor is necessary to limit the inrush current. At startup, the motor has low back electromotive force (EMF) due to its initial stationary state, leading to a potentially very high current that could damage the motor windings or the power supply. The resistance helps to gradually increase the current as the motor accelerates, allowing it to reach its operational speed safely. Once the motor is up to speed, the resistance can be removed or reduced to improve efficiency.
What motors is used in railway engines for traction?
dc series motor :A series-wound DC motor has a low resistance field and armature circuit. Because of this, when voltage is applied to it, the current is high. (Ohms Law: current = voltage/resistance). The advantage of high current is that the magnetic fields inside the motor are strong, producing high torque (turning force), so it is ideal for starting a train. The disadvantage is that the current flowing into the motor has to be limited, otherwise the supply could be overloaded and/or the motor and its cabling could be damaged.
High resistance in parallel connected with galvanometer to form voltmeter?
That won't work. To convert an ammeter (a galvanometer is a very sensitive type of ammeter) you connect a high value resistor in series with it.
How a current limit starter works for an electric motor?
it consists of a series of resistances, a magnet and a bar that is pulled by the magnet. Initially all the resistance comes in series so the current is limited. when the bar is pulled towards the magnet slowly the resistance decreases and the current increases. thus it protects the DC motor from initial high current.
Why should you be the internal resistance of the very few Amitr?
ammeter connect in series in circuit to measure the current, if the Ammeter have a high resistance it would effect the voltage value because there will be a drop voltage over the internal resistance of the Ammeter, so we desgin the ammeters with very low resistance...
For bulbs connected in series the high watt bulb has high resistance?
No, the highest wattage bulb will have the lowest resistance.
Why the series motor is started with some initial load?
In dc motors Speed is directly proportional to back emf and inversely proportional to flux i.e N∝(Eb/φ) In series motor back emf is practically constant. So if we start motor without any load Flux will be small and so speed will be very high. if we start motor without any load it will gain very high speed and may get damaged due to centrifugal forces. Series motor have very high starting torque and used where high starting torque is required.
A galvanometer can be converted into a voltmeter by placing?
a high resistance in series
Why no load-speed of a dc series motor is very high?
high torque
Why ac motor has low power factor?
because of high resistance in the load.
Will a dc motor start if its field resistance is high?
Yes, it will still start.
What is Advantages of using a series DC motor?
The DC series motor is a high torque motor. so that it can pull heavy loads such as traction, lifts etc., the control of speed of a DC series motor is very smooth and easy.
