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1.2 SPEED –TORQUE EQUATION OF DC MOTOR 1.2.1 Electrical motor characteristics The mechanical characteristic of electric motors is the linearity between the speed andthe speed of the moto

In the technological innovation and modernization of water, the problem of applyingscience and technology to regulated products is the most urgent issue Along with thedevelopment of a number of industries such as electronics, information technology Industry automation company has also developed dramatically Process productionautomation is very popular, can replace human labor, high productivity again, goodproduct quality.

Along with the development of the power electronics industry, the application of DCmotors and industry is very important The use of 1-way motors for many purposes such

as to ensure the technological requirements of the load To understand the role of electricdrive system, power electronics and one-way electric motor through this subject project,under the guidance of Mr Nguyen Ngoc Khoat with the main content of the subject: Design a rectifier to control speed of a separately excited DC motor with thefollowing parameters:

1) Half-wave three-phase controlled rectifier; 3x380V, 50Hz

2) DC motor: P = 10 kW, Uđm = 400V, nđm = 1480v/p, Iđm = 10A, Mc = 60%Mđm

I sincerely thank Mr Nguyen Ngoc Khoat for his dedication and help for guiding, helpingand creating favorable conditions for us to complete this topic

CHAPTER I: OVERVIEW OF DC MOTOR1.1General structure

1.1.1Concept

A DC motor is a DC machine that converts direct current into mechanical energy

When a DC machine is operating in the motor mode, the input power is theelectromechanical power and the output power is the mechanical power

1-Plate, 2-Main pole with field coil, 3-Commutating with reel, 4-Ball bearing box, Laminated, 6- Armature roll, 7- Brush equipment, 8 commutator, 9- Axis, 10- Terminal box cover.

5-1.1.3 Classification of DC motors

DC motors are classified according to excitation into the following categories:

• Independent DC motor: The armature and the exciter are supplied from twoseparate sources

• Parallel dc electric motor: The field coil is connected in parallel with thearmature

• Series magnetic dc motor: The exciter coil is connected in series with thearmature

• Combined d.c electric motor: Consists of two excitation windings, oneconnected parallel to the armature, one connected in series with the armature.1.1.4 Principle of DC electric motor

DC motors operate based on the effect of a magnetic field on the wire frame with electriccurrent flowing through the magnetic field When operating DC motors turn the electriccurrent of direct current into mechanical energy

1.2 SPEED –TORQUE EQUATION OF DC MOTOR

1.2.1 Electrical motor characteristics

The mechanical characteristic of electric motors is the linearity between the speed andthe speed of the motor:M = f(ω)

1.2.2 Wiring schematic diagram of an independent dc electric motor

Independent DC motor: DC power is supplied to the armature and supplied to the exciterindependently

Figure 1.3: Wiring schematic diagram of separatedly excited dc motor

• Equation of voltage balance:

Figure 1 4: Speed –Current

• Speed – Torque characteristic:

(1.5)

Figure 1 5: Speed – Torque

1.2.3 Natural Speed -Torque characteristic

Natural mechanical properties: = f (M) when parameters such as U, I, R of the motor are the rated parameters on the natural mechanical properties we have a rated working point is (; ) - Each motor has only 1 natural mechanical property

• Natural Speed –Current characteristic:

(1.6)

• Natural Speed -Torque characteristic:

(1.7)1.2.4 Artificial Speed -Torque characteristic

Artificial mechanical characteristics: = f (M) when the electrical parameters are not ratedparameters or when the electric circuit has been added Rf, Lf - Each motor has many artificial mechanical properties

• Speed -Torque characteristic:

(1.8)1.3 METHODS OF ADJUSTMENT CHANGE ENGINE SPEED DC

1.3.1Change the auxiliary resistance in the armature circuit

Speed -Torque characteristic:

• Ideal constant idle speed

• Only allows speed change adjustment on the downward side

• As Rf increases, the greater the slope of the mechanical properties, the softerthe mechanical properties ⇒ the lower the speed stability, the greater the speederror.

• Power loss in the form of heat on the auxiliary resistor

If we increase Rfto a certain value, it will make M ≤ Mc so that the motor will not spin and the motor is in short circuit mode (ω = 0).From now on, we can change the Rf and thespeed will remain 0, which means the engine speed cannot be adjusted

anymore.Therefore this adjustment method is not a radical adjustment method

Advantages: The changing device is very simple, often used for crane motors, elevators,

lifters, and excavators

Disadvantages: The lower the adjustment speed, the greater the input resistance value,

the softer the mechanical properties, the reduced stiffness leads to poor speed stability when the load changes poorly.The auxiliary losses are very large when adjusting, the lower the speed, the higher the auxiliary losses

The Rfchange method is suitable only when starting the engine

1.3.2 Change of motor magnetic flux

Speed -Torque characteristic:

(1.10)

We see that when changes, and Δω both change, so we will get the curves adjusted

gradually and higher than the natural mechanical properties when ϕ is smaller, with the same load, the higher the speed when reducing the fluxϕ

Figure 1 7: Speed adjustment characteristic by change ϕ

Adjustment characteristics:

• Decreasing the flux results in inversely proportional change of speed Thelower the flux, the more ideal idle speed increases, and the greater themotor speed.

• Constant short-circuit current

• Mechanical property stiffness decreases with decreased flux

If is too small, it may cause the motor speed to exceed the permissible limit, or make the switching condition worse due to the increased armature current.Thus, to ensure normal switching, it is necessary to reduce the armature current ⇒ the torque on the motor shaft rapidly decreases ⇒ the motor is overloaded

Advantages: The speed adjustment method by varying the flux can be infinitely adjusted

and gives the speed greater than the basic speed.The bouncing method is often used formachines such as: universal grinder, bed planer, The adjustment is done on the excitercircuit so the loss of energy is low, the equipment is simple so the price is low

Disadvantages: Due to deep adjustment, β decreases, large static error, less stable with

high speed.That means the deeper the adjustment, the larger Δω.So the more thecharacteristic is that the smaller the torque is until the smaller the load torque, the motorcannot run

1.3.3 Change of motor armature voltage

Speed -Torque characteristic:

(1.11)

We see that when Uưchanges, changes and Δω = const, so we will be adjusted parallel by the property lines But if you want to change Uư, you must have a DC power supply that can change the output voltage, often using a converter

Figure 1 8: Speed adjustment characteristic by Uư change

Adjustment characteristics:

• The motor speed increases / decreases in the direction of increasing / decreasingthe armature voltage

• Variable both ideal no-load speed ω_o, and short-circuit current

• Mechanical property hardness remains constant throughout the adjustment range

• Speed can only be adjusted on the downward side because it can only be changedwith

UưUđm

Advantages: The speed control method by varying the motor armature voltage will keep

the characteristic line stiffness, so it is widely used in metal cutting machines.Ensuringeconomy, low energy loss, wide range of adjustment.If combined with the fluxadjustment method, we can adjust the higher and smaller speeds than the rated speed

Disadvantage: This method requires a power supply that can smoothly change voltage.

CHAPTER II: STRUCTURE CALCULATION ANALYSIS.

2.1 Choose the driving circuit

As mentione20d in Chapter II, I chose the dynamic circuit as a controlled 3-phase rayrectifier

Circuit diagram as shown below:

Figure 2.1: Dynamic circuit

2.2 Dynamic transformers calculation.

Select a three-phase transformer with Y / Y0 wiring diagram, natural air cooled

2.2.1 Calculate the rectifier without load

Udo = Ud, kt = Ud + Uv + UR + UX

Inside: Ud: Rectifier voltage required

Uv: pressure drop on the valve

UR: voltage drop across net resistor

UX: pressure drop caused by switching phenomenon

Select the relative voltage drop across the winding resistance: eR =4%

Relative voltage drop across dissipation power: eX = 7%

The voltage drop across the resistors is:

The voltage drop across the resistors is:

2.2.2 Transformer parameter calculation

- Primary r.m.s MBA: I1 = I2 / kba = 32,396 (A).

2.3 Calculate and select basic parameters of the force circuit

2.3.1.Select the dynamic valve

- Select the dynamic valve.: Iv = Id /3 =7.63 (A)

The maximum reverse voltage applied to the valve, taking into account the highestsource voltage (more than 10% of rated) is:

Assuming natural cooling conditions, the valve mounts onto the radiator:

Select valve with minimum allowable flow: 20,85 (V)

The selector valve has an overvoltage reserve factor ku =2

It mean Umax > 2Ung.max =2* 418.4 = 836,88(V)

2.3.2 Choose thyristor

With the current and voltage parameters, we choose Thyristor T10_80 (according

to the table 2.2.1, page 429, manual capacity electronic design), the followingparameters:

Itb Iđỉnh Irò Umax du/dt tph di/dt ∆U Idk Udk

80(A

)

1200 (A)

6(A) 1200

(v)

1000 (V/µs)

100 (µs)

150 (A/s)

2,7 (V)

150 (mV)

4(V)

Maximum allowable average current through the valve: Itb

Peak current: Iđỉnh

Leakage current when the valve is locked: IR

Maximum voltage the valve can withstand: Umax

Maximum forward voltage rise rate: du / dt

Valve lock recovery time: tph

Value of current growth rate: di / dt

Forward pressure drop for valve: ∆U

Control current: Iđk

Minimum control voltage for valve opening: Uđk

2.3.3 Overvoltage protection for the valve

Overvoltage protection due to the switching thyristor is protected by connecting

R-C in parallel with the thyristor When there is a switch, the electrolytes

accumulated in the semiconductor layers emit outward currents for a short period

of time, the rapid variation of the current produces a very large inductive electric charge in the inductors, make overvoltage between anode and katot on thyristor When there is R-C connected in parallel with the thyristor, it creates a circuit of charge room during the switching process, so the thyristor does not overvolt

We choose parameters R1 and C1 as follows:

R1 = 5 – 30 ()

C1 = 0,25 - 4 ()

2.4 Determine the scope of the control angle

- Select the minimum opening angle: α_min = 10 ° with this opening angle as thereserve angle we can compensate for the drop in grid voltage

- When the opening angle is minimum then the voltage on the load is max

- - When the opening angle is greatest then the voltage on the load is min

Since then we have:

+ Rated current: Iđm = 10A.

CHAPTER 3: SELECTION AND ANALYSIS OF THE CONTROL NETWORK

3.1 Theoretical basis of the Thyristor control

Thyristor is only open for current to flow when there is a positive voltageapplied to the anode pole and there is a positive voltage pulse applied to thecontrol pole, after the Thyristor is opened, the control pulse no longer works,current flows through the Thyristor due to the parameters of the dynamiccircuit decided and the Thyristor will lock when the current flowing through it

is 0, if we want to reopen, we must supply the control pulse again

Therefore, with sinusoidal voltage, depending on the time of impulsecontrol that we can control the current of Thyristor To achieve these features

we can use the following two principles:

- Principle of horizontal control

- Principle of vertical control

Currently, controlling Thyristor in rectifier diagram, people often use the principle of vertical control, so I use this method to design the control circuit

The content of this method:

Figure 3.1: Structure diagram of horizontal control principle

Structure diagram and illustrative graph as shown Here, Uua generates a

quasi-voltage that has a fixed (usually serrated) form, which is cyclic due to Udb's

synchronous rhythm The SS comparison stage determines the equilibrium of the two voltages U-U and U to initiate the TX pulse generation Thus, in this principle, the

pulse timing or valve opening angle changes due to the change in the value Uđk

Figure 3.2: For example control structure circuit graph

3.2 Control circuit structure.

The control circuit includes the following basic stages:

Figure 3.3: Control circuit structure

3.3 synchronous

- Select the synchronous circuit two half cycle:

Figure 3.4: Synchronous circuit diagram

The two half-cycle rectifier circuit has a midpoint using diodes D1, D2 and the

rectifier load is resistor R0 The rectifier voltage Ucl after being created is brought to the (+) pole of the Opam to compare with 0 (because the (-) pole of the opam is

grounded)

If Ucl> 0 then Udb is equal to the saturation voltage (Ubh)

If Ucl> 0 then Udb is equal to the negative saturation voltage (-Ubh).

The point of intersection of Ucl and 0 is the transition point of the output voltage

Figure 3.5: Oscillation graph synchronous circuit diagram

3.4 Stitch creating serrated

Hình 3.6: Circuit Stitch creating serrated

- Calculation:

Cycles: T = 1 / f = 0,02 (s) = 20 (ms)

select OA species TL082 The control angle range is 168 degrees

Capacitor C launch time: tp = = 9,33 (ms)

Choose the voltage regulator diode BZX79C has UDZ = 10 (V)

Select capacitors C = 220 (nF)

select R6 = 51k serial variable resistor P1 = 8k

Time capacitor C loaded: tn = T/2 – tp = 10 – 9,33 = 0,67 (ms)

The saturation voltage of the OA: Udb = E – 1,5 = 12 – 1,5 = 10,5 (V)

So select R4 = 1 (k)

Figure 3.7: Oscillation graph Circuit Stitch creating serrated

3.5 The comparison stage.

Function: Compare the control voltage with the restraint voltage to determine thetiming of the control pulse ⇒ Determine the control angle α

The comparison stage can be done with an element such as a transistor, or an OAalgorithm amplification

- We use the OA element because it allows to ensure the highest accuracy is to usededicated OA coparator, with low cost, without complicated adjustment

- Comparison using two-door OA:

Hình 3.8: Comparison circuit

The two voltages to be compared are applied to two different poles of the OA

In the above case Uđk = U +, Utua = U

-If UDC> Ura ⇒ Ura = + Ubh

If Uđk <Upon ⇒ Ura = - Ubh

Valve selection calculation:

Select Opam type TL082.

Select resistance R1 = 10k, R2 = 10k

Udk = 4 (V)

Hình 3.9: Oscillation graph comparison circuit

3.6 Stitch creating pulse clusters

To create beam pulses we create oscillating pulses and then combine with

phase-synchronized pulses

- - Create pulsed pulses: we use Opam to create oscillating pulses, Opam is used

as a two-door comparator