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connects the brushes to obtain a good commutation.

its also a line joining two points at which no emf is induced.

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Why is brushes placed at MNA in a dc generator?

to avoid sparking ,since their is no e.m.f induced in magnetic neutral axis.


What is the EMF for DC machines?

Electro Magnetic Field


Armature reaction in a DC generator?

ARMATURE REACTION in DC MachineAll current-carrying conductors produce magnetic fields. The magnetic field produced by current in the armature of a dc generator affects the flux pattern and distorts the main field. This distortion causes a shift in the neutral plane, which affects commutation. This change in the neutral plane and the reaction of the magnetic field is called armature reaction.


Can a DC motor work on an AC supply?

There is a motor that is known as Universal motor which works on DC or AC .You might find one in a drilling machine or a domestic grinding machine .But there is a disadvantage ,in that there will be sparking at the commutator between the brushes and the commutator segments due to a shift in the magnetic neutral axis while on AC operation.


What is armature reaction in dc machines?

Armature reaction is the phenomenon in DC machines where the magnetic field produced by the current flowing in the armature windings interacts with the main magnetic field produced by the field windings. This interaction can distort the main magnetic field, causing changes in the machine's performance such as voltage regulation and torque production. Measures such as interpoles or compensating windings are used to counteract the effects of armature reaction in DC machines.


How does a DC electromagnet work and what are its applications?

A DC electromagnet works by passing an electric current through a coil of wire, creating a magnetic field. This magnetic field can attract or repel objects made of magnetic materials. Applications of DC electromagnets include use in electric motors, generators, relays, MRI machines, and speakers. They are also used in industrial applications such as lifting and moving heavy objects using magnetic cranes.


What is mechanical loss in dc machines?

Friction and windage causes mechanical loss in DC machines.


Why transformer not produce DC current?

because transformer in made inductorAlternative AnswerTransformers are AC machines, and do not work with DC. This is because they require an alternating current to set up an alternating magnetic flux which then induces an alternating voltage into its secondary. Remember, there has to be a changing magnetic flux and a conductor for an emf. to be induced into that conductor.


What is the principles of DC machines?

All DC machines are works based on the principle of FARADAY'S LAW OF ELECTROMAGNETIC INDUCTION.


Why do you give DC excitation to AC Synchronous motor?

If the synchronous motor is running near synchronous speed, it will begin rotating at synchronous speed when DC is applied to the rotor. Source: Electrical Machines, Drives, and Power Systems Theodore Wildi Section 17.3


Why are the brushes of a dc machine always placed at the neutral points?

The function of brush is to collect current from rotating commutator and supplies the current to external stationary load. The brushes of a DC machine are placed at neutral points because the current in the rotating part drops to zero at the neutral point. If brushes are placed in location other than the neutral points, then the current may be switched off and it causes magnetic field and it may also create voltage spikes and arc at brushes.


How can the field coils of DC machines be connected with self excited machines?

No