- In Dc Machine The Number Of Slots Per Pole Usually Lies Within
- In Dc Machine The Number Of Slots Per Pole Usually Lies Beneath
- In Dc Machine The Number Of Slots Per Pole Usually Lies Given
- In Dc Machine The Number Of Slots Per Pole Usually Lies Across
The number of slots per pole per phase determines how the winding layout is arranged. It is also disclosing information about the winding factor and its harmonics.
Question: 12 Given A DC Machine That Has The Following Design Features: Connection: Separately-Excited; Rated Voltage: 530 V; Number Of Poles: 4; Number Of Armature Slots: 75; Number Of Conductors Per Slot: 8; Resistance Of Each Conductor: 0.01 2; Winding: Double -Layer Wave; Flux Per Pole: 25 M Wb. At A Speed Of 1000 RPM, The Value Of The. University of Babylon Electrical machines mechanical department If there are P poles on the machine, then the portion of the area associated with each pole is the total area A divided by the number of poles P: P rl P A AP 2π = = The total flux per pole in the machine is thus P rlB P B rl BAP π π φ (2 ) 2 = = =. It is usually measured in terms of teeth, slots or electrical degrees. If the coil-span (or coil-pitch) is equal in case the coil-pitch is to the pole-pitch, then the coil is termed a full-pitch coil. Less if there are S slots and P poles, then pole pitch 𝑸𝑸= 𝑺𝑺 𝑷𝑷 slots per pole. Therefore Slot/pole/phase for the considered example is 4.5 / 3 = 1.5 This means, the R phase conductor occupies 1 full slot and shares half a slot with a conductor of B phase (following RYB sequence.While winding sequence goes counter way) and along with this, one full slot would contain conductor of B phase only. The iron of the machine, the flux per pole is a nonlinear function of the field current. Generated voltage of a DC machine is a linear function of the flux per pole, so it is also nonlinear with respect to the field current. N1 per pole held constant.
If the number of slots/pole/phase is an integer, the winding is called integer-slot winding.
If the number of slots/pole/phase is fractional and superior to 1, the winding is called fractional-slot winding.
If the number of slots/pole/phase is fractional and inferior to 1, the winding is called concentrated winding.
Windings with the same number of slots/pole/phase $q$ have the same winding factor. Their winding layouts consist of the same basic sequence repeated by the number of winding symmetries (or machine periodicity).
Example:
10-pole 12-slot single-layer 3-phase winding: $q=frac{12}{10cdot 3}=frac{2}{5}$, fundamental winding factor: 0.966, one winding symmetry.
20-pole 24-slot single-layer 3-phase winding: $q=frac{24}{20cdot 3}=frac{2}{5}$, fundamental winding factor: 0.966, two winding symmetries.
The number of slots/pole/phase is also an indicator about what winding factor and winding-factor harmnoics one can expect.
Example 1:
The harmonic spectrum of the winding factor of 4-pole 3-phase integer-slot windings in Fig. 1 shows that an increasing number of slots/pole/phase (from $q=1$ for the 12-slot winding to $q=5$ for the 60-slot winding) leads to a steady decrease of the fundamental winding factor. However, since the coils are distributed over several slots per pole per phase, the back-EMF gets more sinusoidal. This fact is reflected in significantly reduced winding factor harmonics of order three and higher, cf. Fig. 1.
Fig. 1 Winding factor harmonics for 4-pole 3-phase integer-slot windings with different number of slots/pole/phase.
Example 2:
For concentrated windings, the fundamental winding factor increases and decreases as a function of the number of slots/pole/phase as shown in Fig. 2. The highest fundamental winding factors are found when the number of slots is closest to the number of poles, ie. $q0007pprox 1/3$.
Fig. 2 Fundamental winding factor for concentrated windings as a function of the number of slots/pole/phase [1].
In Dc Machine The Number Of Slots Per Pole Usually Lies Within
References:
[1] Florence Meier, Permanent-Magnet Synchronous Machines with Non-Overlapping Concentrated Windings for Low-Speed Direct-Drive Applications, Phd Thesis, Royal Institute of Technology (KTH), July 2008
Read about another glossary term
A Motor is a machine that converts electrical energy into mechanical energy. There is no difference between a DC motor and DC generator from a construction point of view. The only difference is that the generators are usually operated in more protected locations and, therefore, their construction is generally of the open type.
On the other hand, motors are generally used in locations where they are exposed to dust, moisture, fumes and mechanical damage. Thus, the motor requires protective enclosures.
For example – Motor requires drip-proof, fire-proof, etc. enclosure according to the requirement. The DC motors are very useful where a wide range of speeds and good speed regulation is required, such as in the electric traction system.
As the construction of DC Motor is similar to DC Generator, which is discussed in the topic Construction of DC Generator. Thus, for the construction of a DC motor refer the link given below. There are various types of DC Motors. They are Shunt motor, Series motor and Compound motor.
Also See:Construction of DC Generator
The EMF equation of DC Motor is given by the equation shown below:
Where,
- Eb is the induced emf of the motor
- N is the speed
- P is the number of poles
- ϕ is the flux per pole.
- Z is the total number of conductors
- A is the number of parallel paths
Equivalent Circuit of a DC Motor Armature
The armature of a DC Motor can be represented by an equivalent circuit. It can be represented by three series-connected elements E, Ra and Vb. The element E is the back emf, Ra is the armature resistance and Vb is the brush contact voltage drop.
The equivalent circuit of the armature of a DC motor is shown below:
In Dc Machine The Number Of Slots Per Pole Usually Lies Beneath
In a DC motor, the current flows from the line into the armature, against the generated voltage. By applying KVL,
Where,
- V – Motor terminal voltage
- Eb – Back EMF
- Ia – Armature current
- Ra – Armature circuit resistance
The equation (1) written above is called the fundamental motor equation. It is seen that the Back EMF of the motor is always less than its terminal voltage V. The equation can also be written as shown below:
In Dc Machine The Number Of Slots Per Pole Usually Lies Given
The equation (2) is considered or applicable when the voltage drop Vb in the brushes is also taken into account.