when the rheostat kept in minimum to maximum position in
motors what will happen?
Answer Posted / bhavani
In dc motor v=Eb-IaRa is the voltage equation.at starting Eb=0 so V=IaRa and the armature resistance is very small nearly 0.01ohm.so Ia increases ,to avoid this problem we kept 3-point starter.in motors field resistance is kept in minimum in order to get high starting torque.if v increases speed also increase and flux in field rheostat and field current are decreases. at the instant of starting to control the speed not to go beyond its rated value.that's why we kept field resistance in minimum.If we kept in maximum,R increases,I decreases,N increases so the motor will exceed its rated speed,then motor will damaged.or to avoid this probiem,we can control the speed of motor ,when armature rheostat is in maximum,voltage applied is minimum,so N decreases.so we will get rated speed by controlling any one of this.either by incresing applied voltage to armature or by decreasing the current in field winding.THANK YOU
Is This Answer Correct ? | 4 Yes | 0 No |
Post New Answer View All Answers
I have a CT meter with ratio 60/5. The meter reading of previous month was 3290.49 and that of current month was 3797.26. How many chargeable units as per normal meter should be my reading.
Transmission voltage is kept 11KV,33KV,66KV,132KV,220KV due to form factor. What happen to 400KV and 765KV transmission voltage?
Why the efficiency of a three-phase induction is the motor is less than that of a three-phase transformer?
Define corner frequency?
hi,every one, i have to write the search paper on "performance policy optimization" of NGN (next generation networks). i need the material on this topic. can any body help me. please tell me any useful site where the good material is available and name of any reference book. it should be a great help for me.
need to make a report. Need to choose a 3phase induction motor. Load conditions motor will operate in : Maximum Load: 30 Kw Speed: 2950 rpm Ambient temp: 20 cent Supply voltage: 440V Frequency: 50Hz need to look for the safety factor when choosing the motor, went through catalouge found a few, but dont know how to choose the safety factor allowing an extra load something above 30 KW to avoid any harm.
What is synchro?
How many gap between finger contact in a.c.b. and v.cb.?
How the circuit breaker is selected for Induction motor of 100 kW, 415 volt, 0.85 power factor, 0.95 efficiency ?
Single line diagram for dbb (double bus bar)system.
HOW DOES THE ELECTRONIC ENERGY METER WORKS?
how we calculate torque ? how we improve it ?where torque will either motor or generator ?
what are the components in electrical control panel (for example: 415V, 3-ph, panel to operate utility and 3-ph DG set).
what is the reason the main breaker is trip during the motor is running? (some time the breaker is not trip)
Why is the starting current high in dc motor?