ارماتور: پێناسە، کاروبار و بەشەکان (موتوری برق و ژێنەری)
Armature çi ye?
Armature electric machine (motor an jêenerator) de parçeyek dike ku amper cîhanî (AC) hatine. Armature hewce AC dikare, tay maşînên DC (Direct Current) tê kommutator (ku her dema rengin amperiya biguhezîne) an tay electronic commutation (wêla motor brushless DC).
Armature armature winding li ser derbarê wekheviyek da dide û li ser magnetic field ên di air gap de yên stator û rotorê de dibûne. Stator yek ji wan partên bûyer (rotor) an pirtûk (stator) be.
Terma armature di navbera 19'în qarnan de hatiye serbest kirin wê ji bo "keeper of a magnet" ne.
Armature di Electric Motor de Ji Çewa Xebite?
Electric motor electrical energy bi karberiyên electromagnetic induction mechanical energy digirin. Her dema conductor bi amperiya li ser magnetic field bikar îne, weha ji bo Fleming’s left-hand rule hewce dikare.
Di electric motor de, stator rotating magnetic field bikar îne bi permanent magnets an electromagnets. Armature, ku ziyadek rotor e, armature winding heke û pişte komutator û brushes e. Komutator direction of the current di armature winding de hewce dikare ta her dema bi magnetic field were.
Interaction between the magnetic field and the armature winding torque bikar îne ku armature xerîbe. Shaft attached to the armature mechanical power to other devices.
Armature di Electric Generator de Ji Çewa Xebite?
Electric generator mechanical energy bi karberiyên electromagnetic induction electrical energy digirin. Her dema conductor li ser magnetic field bike, EMF (electromotive force) ji bo Faraday’s law inducive dikare.
Di electric generator de, armature ziyadek rotor e ku ji prime mover, wêla diesel engine an turbine, werdigire. Armature armature winding heke û pişte komutator û brushes e. Stator stationary magnetic field bikar îne bi permanent magnets an electromagnets.
Relative motion between the magnetic field and the armature winding EMF di armature winding de inducive dikare, ku electric current through the external circuit. Komutator direction of the current di armature winding de hewce dikare ta alternating current (AC) were.
Armature Parts & Diagram
Armature core, winding, commutator, and shaft ji bo sêr parçeyên. A diagram of an armature is shown below.
Armature Losses
Armature electric machine de li ser various types of losses bûne ku efficiency û performance ya were. Main types of armature losses:
Copper loss: This is the power loss due to the resistance of the armature winding. It is proportional to the square of the armature current and can be reduced by using thicker wires or parallel paths. The copper loss can be calculated by using the formula:
where Pc is the copper loss, Ia is the armature current, and Ra is the armature resistance.
Eddy current loss: This is the power loss due to the induced currents in the core of the armature. These currents are caused by the changing magnetic flux and produce heat and magnetic losses. The eddy current loss can be reduced by using laminated core materials or increasing the air gap. The eddy current loss can be calculated by using the formula:
where Pe is the eddy current loss, ke is a constant depending on the core material and shape, Bm is the maximum flux density, f is the frequency of flux reversal, t is the thickness of each lamination, and V is the volume of the core.
Hysteresis loss: This is the power loss due to the repeated magnetization and demagnetization of the core of the armature. This process causes friction and heat in the molecular structure of the core material. The hysteresis loss can be reduced by using soft magnetic materials with low coercivity and high permeability. The hysteresis loss can be calculated by using the formula:
where Ph is the hysteresis loss, kh is a constant depending on the core material, Bm is the maximum flux density, f is the frequency of flux reversal, and V is the volume of the core.
The total armature loss can be obtained by adding these three losses:
The armature efficiency can be defined as the ratio of the output power to the input power of the armature:
where ηa is the armature efficiency, Po is the output power, and Pi is the input power of the armature.
Armature Design
The design of the armature affects the performance and efficiency of the electric machine. Some of the factors that influence the armature design are:
The number of slots: The slots are used to accommodate the armature winding and provide mechanical support. The number of slots depends on the type of winding, the number of poles, and the size of the machine. Generally, more slots result in better distribution of flux and current, lower reactance and losses, and smoother torque. However, more slots also increase the weight and cost of the armature, reduce the space for insulation and cooling, and increase the leakage flux and armature reaction.
The shape of slots: The slots can be opened or closed, depending on whether they are exposed to the air gap or not. Open slots are easier to wind and cool, but they increase the reluctance and leakage flux in the air gap. Closed slots are more difficult to wind and cool, but they reduce the reluctance and leakage flux in the air gap.
The type of winding: The winding can be a lap wound or wave wound, depending on how the coils are connected to the commutator segments. Lap winding is suitable for high-current and low-voltage machines, as it provides multiple parallel paths for current flow. Wave winding is suitable for low current and high voltage machines, as it provides a series connection of coils and adds up the voltages.
The size of the conductor: The conductor is used to carry the current in the armature winding. The size of the conductor depends on the current density, which is the ratio of current to cross-sectional area. Higher current density results in higher copper loss and temperature rise, but lower conductor cost and weight. Lower current density results in lower copper loss and temperature rise, but higher conductor cost and weight.
The length of the air gap: The air gap is the distance between the stator and rotor poles. The length of the air gap affects the flux density, reluctance, leakage flux, and armature reaction in the machine. Smaller air gap results in higher flux density, lower reluctance, lower leakage flux, and higher armature reaction. Larger air gap results in lower flux density, higher reluctance, higher leakage flux, and lower armature reaction.
Armature Design (continued)
Some of the methods used to design the armature are:
EMF equation: This equation relates the induced EMF in the armature to the flux, speed, and number of turns of the winding. It can be used to determine the required dimensions and parameters of the armature for a given output voltage and power.
where Ea is the induced EMF in volts, ϕ is the flux per pole in webers, Z is the total number of conductors in series, N is the speed of rotation in rpm, P is the number of poles, and A is the number of parallel paths.
MMF equation: This equation relates the magnetomotive force (MMF) produced by the armature winding to the current and number of turns of the winding. It can be used to determine the required current and number of turns for a given MMF and flux.
