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Why the armature rheostat of dc is motor kept at maximum resistance position?
Wiki User
∙ 9y ago
It isn't. It is only kept at maximum resistance when the motor is not running. That is done to limit the starting current.
Wiki User
∙ 9y ago
Wiki User
∙ 11y agoto limit the high current
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What will happen if field rheostat of dc shunt motor is kept at maximum position while starting?
First remember this rheostat is connected in series with the armature to increase the total resistance to limit the starting current, thus achieving max starting torque from the motor
Why motor rheostat kept minimum position generator rheostat maximum position?
the back emf increases so that high currents doesn't pass through the field windings
What is the maximum resistance you want to see across a switch?
The maximum resistance across a switch should be infinite.
How do you select field rheostat range for dc motor?
For a shunt dc motor the rheostat would vary from zero ohms to a value that produces the required minimum field current, but rheostats are not common with shunt motors except as a crude way of controlling the speed. Series dc motors normally use rheostats for starting, especially in trams etc. because the starting torque and current is very high. The rheostat resistance starts at a value equal to the supply voltage divided by the maximum allowable current drawn, and is reduced as the speed builds up.
What will happen when source resistance equals load restiance?
when source resistance and load resistance are equal maximum power is transfered
What will happen if field rheostat of dc shunt motor is kept at maximum position while starting?
First remember this rheostat is connected in series with the armature to increase the total resistance to limit the starting current, thus achieving max starting torque from the motor
Why armature rehostat is kept at maximum position?
In a series DC motor used for traction, the armature rheostat is there to limit the current on starting. In normal running the rheostat is set to zero ohms (maximum power) so that power is not wasted in it. At full speed the power is turned off, the vehicle then coasts along until it's time to stop.
What are the values of armature and field rheostat to be maintained during starting of a d.c motor?
you want full field while starting 0 Ohms and maximum series on armature then bring the armature resistance to zero as it approaches running speed its a good idea to run with armature at 0 ohms armature will use the same amount of power as the resistor If you want to run at more than base speed you can now weaken the field
Why motor rheostat kept minimum position generator rheostat maximum position?
the back emf increases so that high currents doesn't pass through the field windings
When the rheostat position is changed from minimum position to maximum position in motors what will happens?
the back emf increases so that high currents doesn't pass through the field windings
Why rheostats have current rating in addition to resistance rating?
A resistor, of which a rheostat is, has a maximum amount of current it can handle. Beyond that value it will start heating up a lot and might burns up. Since, the maximum resistance of a rheostat is fixed so does its maximum safe current value that can flow through it.Comment'Rheostats' and 'potentiometers' describe applications of variable resistors; they are not alternative words for variable resistors.
Why the generator field rheostat kept at maximum position?
There is nothing to limit current until opposing magnetic fields build up at generator operating speed-windings will overheat and burn.
How does a rheostat work?
A rheostat is simply a variable resistor. It is engineered so a "wiper" travels along the resistor carbon path. There is minimum resistance at one end of the path, and maximum resistance (what maximum value the engineers made into it) at the other end. Rheostats come in many values such as "0 to 1000 ohm", 0-1000 ohm, 0-10,000 ohm, and etc., all the way up to mega-ohm values. Some are designed to work on 0-5 watts, 0-20 watts, or larger power versions with resistance wire in them.
What is the maximum resistance you want to see across a switch?
The maximum resistance across a switch should be infinite.
What is a rheostat and how it workes?
A Rheostat is a variable resistor, for changing resistance by use of a rotary knob or slider. It is simply a long length of wire with a high resistance value (such as Nichrome), wrapped around a suitable former, such as a cylinder or horseshoe shaped pocelain. One end is connected to a supply and a slider is wiped across the wire. Picking off a resistance anywhere between zero at the supply end, to maximum resistance at the far end. The resistance gets rid of excess voltage by heating up. They can get very hot, so are made of non-comsutible material and housed in ventilated cabinets. They are used for crude systems of lamp dimmers and motor speed control. Largely replaced with modern electronics, which are smaller and run cooler.
Name the three basic methods that are used to vary the speed of a DC motor?
speed of a dc motor can be varied by mainly two methods:- 1)field control method 2)armature control method further , field control method can be divided in 3 parts:- 1)field rhestat control method---speed variation is acomplished by means of a variable resistance inserted in series with shunt field 2)reluctance control method---by changing the reluctance of magnetic circuit by choosing right material.. 3) field voltage control method-requires variable field voltage supply. and armature control method can be divided in 3 parts :- 1)armature resistance control---variable resisitance connected in series with armature 2)shunted armature control. 3)armature voltage control. ------------mrityunjay pandey (kiit university ,btech 2nd year)
How do you select field rheostat range for dc motor?
For a shunt dc motor the rheostat would vary from zero ohms to a value that produces the required minimum field current, but rheostats are not common with shunt motors except as a crude way of controlling the speed. Series dc motors normally use rheostats for starting, especially in trams etc. because the starting torque and current is very high. The rheostat resistance starts at a value equal to the supply voltage divided by the maximum allowable current drawn, and is reduced as the speed builds up.
