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if there are magnets on the stator
and the commutator is phased properly
this is known as a permanent magnet dc motor
the starting torque is dependent on armature current and the strength of the magnet
the speed is directly proportional to the armature voltage
a shunt motor needs the field energized for starting.
more field more starting torque
What else can I help you with?
Would the motor turn if only the armature were excited?
A motor will turn when only the armature is excited, if there is enough residual magnetism in the field.
Does the motor speed double when the armature voltage is doubled?
Yes, because as the armature voltage increases, the speed also increases so they are proportional.
Why the armature current of a shunt motor decreases as the motor accelerates?
Without a mechanical load the motor accelerates until the back-emf generated by the armature nearly equals the supply voltage. On load, the speed drops and the current rises until the power taken from the supply balances the mechanical power supplied to the load. If the armature has low resistance, the speed drop under load is not very much, so speed regulation is better if the armature resistance is lower.
If you were to mechanically rotate the armature in an electric motor what would happen?
You said "armature" so it is a dc motor. Hence if the field is permanent magnet type then a voltage appears at the armature terminals nd its magnitude depends on the speed nd magnetic field strength. If it's field coils, then they must be seperately excited (if it don't possess residual). By changing the field strength you can vary the voltage produced at armature terminals.
What is separately excited DC motor?
The main difference between the Separately excited motor and the shunt motor is the field cct where as in the second it has its own voltage supply.AnswerI think you mean 'generator', not 'motor'. A 'self-excited' motor is one in which the output supplies the field current, as well as the load current. A 'separately-excited' motor is one in which the field current is provided from an external source.
What part of the motor is current supplied to on a ac motor?
commutator, armature
Would the motor turn if only the armature were excited?
A motor will turn when only the armature is excited, if there is enough residual magnetism in the field.
Does the alternating current supplied to the armature winding of a DC motor gets converted to dc by a commutator before it flows through the armature coil of the DC motor?
The commutator is a rotating switch, which reverse the polarity of the generated voltage every half-cycle. So it acts to rectify the output voltage.
Would it be correct to say ' with a fixed field voltage the speed of a shunt motor is proportional to its armature voltage?
Yes, it is correct to say that with a fixed field voltage, the speed of a shunt motor is proportional to its armature voltage. This relationship arises because, in a shunt motor, the back EMF (electromotive force) is dependent on the speed and armature current. As the armature voltage increases, the armature current increases, leading to a higher speed until a new equilibrium is reached, assuming the field current remains constant.
Which the effect of the increase of the armature voltage on the speed of a direct-current separately excited motor in case of constant load?
Increasing the armature voltage would increase the speed. In a separately excited dc motor the speed adjusts so that the back emf generated by the armature is a little less than the supply voltage. The difference, divided by the resistance, gives the current drawn, which is also proportional to the shaft torque supplied to the load.
Does the motor speed double when the armature voltage is doubled?
Yes, because as the armature voltage increases, the speed also increases so they are proportional.
Why the armature current of a shunt motor decreases as the motor accelerates?
Without a mechanical load the motor accelerates until the back-emf generated by the armature nearly equals the supply voltage. On load, the speed drops and the current rises until the power taken from the supply balances the mechanical power supplied to the load. If the armature has low resistance, the speed drop under load is not very much, so speed regulation is better if the armature resistance is lower.
What will happen to a motor if it is supplied with lower voltage than its rated voltage?
The amperage to the motor will go higher.
If you were to mechanically rotate the armature in an electric motor what would happen?
You said "armature" so it is a dc motor. Hence if the field is permanent magnet type then a voltage appears at the armature terminals nd its magnitude depends on the speed nd magnetic field strength. If it's field coils, then they must be seperately excited (if it don't possess residual). By changing the field strength you can vary the voltage produced at armature terminals.
Why would a dc motor show high amps no voltage and struggle to turn?
The current flowing in a dc motor is determined by (Applied voltage-Motor EMF) divided by armature resistance. The motor emf is a function of the field excitation of the motor and the speed at which the motor turns. When the motor starts, there can be no EMF because motor speed is 0 rpm. Therefore the motor will draw more current. But as the motor begins to speed up, if it has field excitation, it has to build up EMF and the current will drop. So : If the motor shows high amps and no voltage and struggles to turn the possible reasons are: 1. The motor has no excitation - The permanent magnets are weak or the field winding is faulty or the field is not being supplied. 2. The armature winding is faulty - it has shorted windings. This assumes your supply is healthy of course.
What is separately excited DC motor?
The main difference between the Separately excited motor and the shunt motor is the field cct where as in the second it has its own voltage supply.AnswerI think you mean 'generator', not 'motor'. A 'self-excited' motor is one in which the output supplies the field current, as well as the load current. A 'separately-excited' motor is one in which the field current is provided from an external source.
What is commutation in DC machines?
It is the process of conversion of generated ac voltage into the armature of a dc generator to dc voltage at the terminal of the dc generator by use of pair of brushes and commutator. OR It is the process of conversion of given dc voltage at the terminal of the dc motor to ac voltage in the armature windings in a dc motor by use of pair of brushes and commutator.
