DC Machines – Types of DC motor | DC motor presentations |

Dc machine-types of dc motor

 Dc motor presentations Machines-types of dc motor Construction of a Dc machine consist of main two parts.

  1. Stationary part- It is designed mainly for producing a magnetic flux.
  2. Rotating part- It is called the armature, where mechanical energy is converted into electrical such as an electrical generator.
Fig. DC machine

The stationary and rotating parts are separated from each other by an air gap

  • The stationary part of the dc machine consists of main poles,┬ádc motor definition┬ádesigned to create the magnetic flux, commutating poles interposed between the main poles and designed to ensure sparkless operation of the brushes at the commutator in very┬áStarting of DC motor ppt small machines with a lack of space commutating poles are not used and frame/yoke.
  • The armature┬áconstruction and working of dc motor ppt is a cylindrical body rotating in the space between the poles and comprising a slotted armature core, a winding inserted in the armature core slots, a commutator, and brush gear.
Fig. DC machine

In generator dc or ac, the frame is the stationary part of a machine to which are fixed the main and commentating poles and by means of which the machine is bolted its bed plate. The right shape portion which serves as the part for the main and commutating pole fluxes is called the yoke.

Cast iron was used to dc generator dynamo be the material for the frame/yoke in early machines but now it has been replaced by cast steel. This is because cast iron is saturated by a flux density of about 0.8 wb/ m square while saturation which cast steel is at about dc generator working principle 1.5 wb/m square.  

Dc generator diagram thus the cross-section of a cast iron frame is about twice that of a cast steel frame for the same value of magnetic flux. Hence, if it is necessary to reduce the weight of the machine, cast steel is used. Another disadvantage of the use of cast iron is that its mechanical and magnetic properties are uncertain due to the presence of below holes in the casting & types of dc machines.

 Lately, the application of dc machine rolled steel yokes have been developed with improvements in welding techniques. The advantage of fabricated yokes is that three are no pattern changes and the magnetic and mechanical properties of the frame are absolutely consistent types of dc motor ppt.

It may be advantageous to brushed dc motor ppt use cast iron for frames but for medium and large sizes usually rolled steel is used. If the armature diameter does not exceed 35 to 45 cm, then in addition to the poles, end shields or frame heads that carry the bearings are also attached to the frame. When the armature diameter exceeds 1 m, it is common practice to use pedestal-type bearings, mounted separately, on the machine bedplate outside the frame.

The characteristics of dc motor ppt end shield bearings, and sometimes the pedestal bearings, are of the ball or roller type. However, more frequently plane pedestal bearings are used. In machines with large diameter armatures, a brush-holder yoke is frequently fixed to the frame.

Field poles

Formerly characteristics of different types of dc motors the poles were cast integral with the yoke. This practice is still being followed for small machines. But in present-day machines, it is usual to use either a completely laminated pole, permanent magnet dc motor characteristics, or solid steel poles with laminated pole shoes.

Laminated permanent magnet dc motor construction is necessary because of the pulsations of field strength that result when the notched armature rotor magnetic structure passes the pole shoe. Variations in field strength result in internal eddy currents being generated in a magnetic structure & synchronous motor.  

The electrical motor eddy current causes losses, how electric motors work may be largely prevented by having laminated magnetic structures. Laminated structures allow magnetic flux to pass along the length of the lamination, but do not allow electric eddy currents to pass across the structure from one lamination to another. The end of the laminated pole is a curved electric motor diagram to fit very closely into the main frame.

Fig. Dc machine yoke/body part

Different methods are used for the electric motor principle attaching poles to the yoke. In the case of big sizes, smaller size the back of poles is drilled and tapped to receive the pole bolts. In larger sizes, a circular or rectangular pole bar is fitted to the pole. This pole bar is drilled and tapped and the bolts passing through laminations screw the tapped bar principle of an electric motor.

Fig. yoke/dc machine

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