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it is kept at minimum position to produce more torque which is required for starting a motor
Wiki User
∙ 13y ago
Wiki User
∙ 11y agoE proportional to N
N inversely proportional to flux
min. pos. to ensure that speed does not go beyond rated value and to have high starting torque
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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 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 the armature voltage E changes when the field rheostat is varied?
This depends on how the motor and wiring. You'll need to provide more information. Series / compound / shunt / differential / self or separately excited / is the rheostat in parallel or series to the field / is the rheostat on the shunt field or series field (if compound)
Why is the field rheostat of a DC motor kept at minimum position while starting?
If you are talking about the field rheostat on a generator, once you have the correct voltage output set, it is very unlikely that it has to be touched again. If it is the generator's first start up, then it is best to set the field on the low side so as not to over excite the generator and drive the output voltage higher that what the generator's specifications are rated at. The field excitation voltage does not have to be set at the minimum position on every start up once it is set for the correct output voltage. A good example of this is a hospital standby generator, it starts up with no human intervention needed.
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.
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 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 the armature voltage E changes when the field rheostat is varied?
This depends on how the motor and wiring. You'll need to provide more information. Series / compound / shunt / differential / self or separately excited / is the rheostat in parallel or series to the field / is the rheostat on the shunt field or series field (if compound)
Why is the field rheostat of a DC motor kept at minimum position while starting?
If you are talking about the field rheostat on a generator, once you have the correct voltage output set, it is very unlikely that it has to be touched again. If it is the generator's first start up, then it is best to set the field on the low side so as not to over excite the generator and drive the output voltage higher that what the generator's specifications are rated at. The field excitation voltage does not have to be set at the minimum position on every start up once it is set for the correct output voltage. A good example of this is a hospital standby generator, it starts up with no human intervention needed.
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.
Can a rheostat be used to control speed on a capacitor run motor?
No. If you attempt to reduce the voltage to a cap start motor by using a rheostat, you can destroy the motor.
Can a electrical motor current be increased?
When the coil is parallel to magnetic field, torque is maximum. When the coil is in vertical position, the torque is minimum. You can't go beyond that.
How do you start a DC motor if there is no 3 point starter?
By the use of auto transformer and bridge rectifier we can start dc motor.
Why the armature rheostat of dc is motor kept at maximum resistance position?
It isn't. It is only kept at maximum resistance when the motor is not running. That is done to limit the starting current.
If the rheostat were connected in series with the shunt field winding and the combination placed across a 120 V dc line what shunt field current variations could be obtained from your motor?
It could be anything, it depends on the design of the motor and whether it is a high-power or a low-power motor.
How do you change the speed of a motor in a circuit?
By varying the Resistance to the motor. These Devices are called RHEOSTAT'S
How do you drop the voltage of a 12v dc motor to slow it down?
Install a rheostat in series with the motor.
