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In the case where variable RPM (more than two desired settings for RPM) are required for universal motors, the centrifugal mechanism of RPM control is used. This speed control method is used for universal motors in applications like home food and drink mixers. The setting of RPM is made by a centrifugal switch located inside the motor as shown in the diagram below. This centrifugal switch can be controlled or adjusted by means of an external lever. If the motor speed rises above that set by the lever, the centrifugal device or switch opens two contacts and inserts a resistance R in the power circuit to the motor, which causes the motor speed to decrease. If the motor runs too slowly, the centrifugal device will close the two contacts and short circuit the resistance so that the motor speed rises. This process is repeated so rapidly that variations in speed are not noticeable. A resistance is connected across the centrifugal switch or device to perform this function. A capacitor C is used across the contact points in order to reduce sparking produced due to the opening and closing of these points. Moreover, it prevents pitting the of contacts.

TRƯỜNG ĐẠI HỌC SƯ PHẠM KỸ THUẬT TP HCM

KHOA ĐÀO TẠO CHẤT LƯƠNG CAO



COURSE PROJECT AUTOMATIC ELECTRIC DRIVE

TOPIC PRINCIPLES OF UNIVERSAL MOTOR AND APPLICATIONS

Lecturer: TS Nguyễn Phan Thanh SVTH:

1 Trần Công Trung MSSV:17142079

2 Lê Minh Huy MSSV:17142019

LECTURER’S STATEMENT

TP.HCM, ngày… tháng 12 năm 2020

Giáo viên hướng dẫn

FOREWORDAbout this assignments, we would like to express our gratitude to teachers ofElectrical & Engineering for lecturing us and giving out valuable lessons andexperiments Especially lecturer Nguyen Phan Thanh for helping us about UniversalMotor and guiding us through Automatic Electric Drive project.

During the process, we couldn’t avoid the mistakes, hopefully those won’t causetrouble for our project and once again we would like to express our gratitude to lecturerNguyen Phan Thanh for giving us such a valuable lesson about Universal Motor

CHAPTER 1: OVERVIEW I/BACKGROUND INFORMATION:

For centuries to catch up the demands of the customers, we had createdmachines that mass products with high efficiency and one of the key components tomake the machine works is the motor

II/ OBJECTS AND PURPOSES OF THE PROJECT:

1 Object:

- Getting familiar with general mechanism

- Research, calculate mechanism

- Research the control method

- Research, calculate, design circuit controller of universal motor

2 Purpose:

- Understand the characteristics, fundamental of universal motor

- Get used to with various types of motor especially universal motor

- For future plans

III/ RESEARCH METHOD:

1 Theoretical basic:

- Search, summarize documentaries of universal motor

- Study on stepper motor linearity theory, theory, algorithms, models, andapplied circuit universal motor control in practice

2 Experiment:

- Applying the theory of linearity and control methods of the universal motor invacuum cleaners

CHAPTER 2: THEORETICAL BASIC

I/ OVERVIEW OF UNIVERSAL MOTOR

1 Introduction:

A universal motor is a special type of motor which is designed to run on either

DC or single phase AC supply These motors are generally series wound (armatureand field winding are in series), and hence produce high starting torque That iswhy, universal motors generally come built into the device they are meant to drive.Most of the universal motors are designed to operate at higher speeds, exceeding

3500 RPM They run at lower speed on AC supply than they run on DC supply ofsame voltage, due to the reactance voltage drop which is present in AC and not inDC

a Structure:

Construction of a universal motor is very similar to the construction of a

DC machine It consists of a stator on which field poles are mounted Fieldcoils are wound on the field poles

However, the whole magnetic path (stator field circuit and also armature)

is laminated Lamination is necessary to minimize the eddy currents whichinduce while operating on AC

The rotary armature is of wound type having straight or skewed slots andcommutator with brushes resting on it The commutation on AC is poorer thanthat for DC because of the current induced in the armature coils For thatreason, brushes used are having high resistance

b Operating principle:

A universal motor works on either DC or single phase AC supply Whenthe universal motor is fed with a DC supply, it works as a DC series motor.When current flows in the field winding, it produces an electromagnetic field.The same current also flows from the armature conductors When a currentcarrying conductor is placed in an electromagnetic field, it experiences amechanical force Due to this mechanical force, or torque, the rotor starts torotate The direction of this force is given by Fleming's left hand rule

When fed with AC supply, it still produces unidirectional torque.Because, armature winding and field winding are connected in series, they are

in same phase Hence, as polarity of AC changes periodically, the direction ofcurrent in armature and field winding reverses at the same time.Thus, direction of magnetic field and the direction of armature current reverses

in such a way that the direction of force experienced by armature conductorsremains same Thus, regardless of AC or DC supply, universal motor works onthe same principle that DC series motor works

i. Advantages of universal motor:

Can run from AC or DC supplies

• Is a cheap motor.

• It has good torque at low speeds

ii. Disadvantages of universal motor:

• Brushes and commutator wear out, create sparking which cancause electromagnetic interference and may be an ignitionsource of VOCs

• Speed control is lousy - it has characteristics of series DCmotor

• It is not easy to reverse the motor

c Stator

a Method of stator windings.

Each type of motor has different types of size and magnetic pole so wecannot

use the same mold to wind the wires Each individual motor has their ownmold to wind the wires But because of the Universal Motor characteristic, youonly need one mold to wind the wires

The way to make mold is first take a cooper wire and then bend it thenplace it around the magnetic pole After that, measure it and make a mark thentwist at the end to make a shape like in the picture

After we done the first loop of the copper wires, continue to wind the wires

to match the preference of the machine, (be caution: each loop of copperwinding must be parallel to each other to avoid getting tangled and easy to putin.)

b 3 levels of winding stator.

i First level.

• Step 1: First we look at the statistic of the machine, for example:

if machine is 700 loops then we just only to loop 700 hundredtimes

• Step 2: We took out the previous one out make it as a preferencethen we loop with the new copper wires

• Step 3: After done looping we now shape the new copperwinding to match the previous one, avoid bending too much anddamage to the new copper winding

• Step 4: then we place parallel with the stator of the machine andstart putting it around the magnetic pole

Stretching the copper wires.

• Step 5: Now we use 2 hand to stretch the copper winding at theend of 2 sides, then we place it on stator (avoid getting it bended

ii Second, third level.

• The method is same with the first one but instead of one wemaking two or 3 loops

• Step 1: First we look at the statistic of the machine

Roll speed

• Step 2: We took out the previous one out make it as a preferencethen we loop with the new copper wires.

• Step 3: After done looping we now shape the new copperwinding to match the previous one, avoid bending too much anddamage to the new copper winding

• Step 4: then we place parallel with the stator of the machine andstart putting it around the magnetic pole

• Step 5: Now we use 2 hand to stretch the copper winding at theend of 2 sides, then we place it on stator (avoid getting it bended

or tangled)

Principle of machine

V source

• Step 6: After done placing we now check again if there is anytangled part or damaged.

• Step 7: Make sure the winding doesn’t touch the outer part of themachine and test the smoothest when rotate

• Step 8: After that we use VOM to check and measure theinsulation of the wires After that we apply tape and PVE forsafety use (insulation must be greater than or equal to 1MΩ)

3 Rotor

a Method of rotor winding.

ii Folded winding.

• Step 1: - Mark the number of motor grooves from 1-Z and markthe end of the wire, the first wire will be on the commutator

- Armature winding consists of many componentsconnected together according to a certain rule.

- The winding consists of one bundle of copper wireswith one loop or many loops that its two ends are connected eachother into plates and make a closed loop

• Step 2: Insulate the insulating cover in the motor groove

• Step 3: Conduct winding wire one by one into the groove of therotor according to the manual of the motor

• Step 4: Check if there is any faults (note: if the wire hasF>0.15mm, the wire connecting to commutator plates must bethreaded with an insulated pipe

Copper wires

Commutation plates

• Step 5: Checking on rotor:

- Check the insulation between the winding wire andmetal part of the rotor

- Check the welds on the commutator plate

• Step 6: Assemble the motor

- Check energizing

- Check the mechanical part by using hand to rotate therotor until it smooths

- Check the circuit (using VOM)

- Check the insulation between the wires and outer part ofthe motor (using VOM)

- Check the supply

- Run the motor to check the value and direction

iii Wave winding.

• Step 1: - Mark the number of motor grooves from 1-Z and markthe end of the wire, the first wire will be on the commutator

- Armature winding consists of many components

connected together according to a certain rule

- The winding consists of one bundle of copper wireswith one loop or many loops that its two ends are connected eachother into plates and make a closed loop.

• Step 2: Insulate the insulating cover in the motor groove

• Step 3: Conduct winding wire one by one into the groove of therotor according to the manual of the motor

• Step 4: Check if there is any faults (note: if the wire hasF>0.15mm, the wire connecting to commutator plates must bethreaded with an insulated pipe

- Check the insulation between the winding wire andmetal part of the rotor.

- Check the welds on the commutator plate

• Step 6: Assemble the motor

- Check energizing

- Check the mechanical part by using hand to rotate therotor until it smooths

- Check the circuit (using VOM)

- Check the insulation between the wires and outer part ofthe motor (using VOM)

- Check the supply

- Run the motor to check the value and direction

iv Shunt winding.

Note: the total grooves on the motor must be an even number, if thenumber bundle is even number then the shunt bundles will becontinuously wound and separated by 2 grooves

If the number of bundles is odd number then the shunt bundles will beindependently wound and separated by 2 grooves

• Step 2: Insulate the insulating cover in the motor groove.

• Step 3: Conduct winding wire one by one into the groove of therotor according to the manual of the motor

• Step 4: Check if there is any faults (note: if the wire hasF>0.15mm, the wire connecting to commutator plates must bethreaded with an insulated pipe

• Step 5:

- Lower case: Pair first shunt bundles 1-6; 7-12

Pair third shunt bundles 3-8; 2-9

Pair fifth shunt bundles 5-10; 4-11

- Upper case: Pair the second bundles 6-11; 5-12

Pair the fourth bundles 8-1: 7-12

Pair the sixth bundles 4-9; 3-10

• Step 6: Checking on rotor:

- Check the insulation between the winding wire andmetal part of the rotor.

- Check the welds on the commutator plate

• Step 7: Assemble the motor

- Check energizing

- Check the mechanical part by using hand to rotate therotor until it smooths

- Check the circuit (using VOM)

- Check the insulation between the wires and outer part ofthe motor (using VOM)

- Check the supply

- Run the motor to check the value and direction

v V winding.

Note: the bundles must be an even number

Beginning and the end of the last bundles must be forming a V shape.And V shape must be symmetrical

• Step 1: Sketch and draw on a paper

• Step 2: Assemble the upper and lower case wound.

• Step 3: Determine the output that connect to the commutationplate.

• Step 4: Draw the wounding

- Armature winding consists of many componentsconnected together according to a certain rule.

- The winding consists of one bundle of copper wireswith one loop or many loops that its two ends are connected eachother into plates and make a closed loop

• Step 6: : Insulate the insulating cover in the motor groove

• Step 7: Conduct winding wire one by one into the groove of therotor according to the manual of the motor

• Step 8: Check if there is any faults (note: if the wire hasF>0.15mm, the wire connecting to commutator plates must bethreaded with an insulated pipe

• Step 9: Checking on rotor:

- Check the insulation between the winding wire andmetal part of the rotor

- Check the welds on the commutator plate

• Step 10: Assemble the motor

- Check the insulation between the wires and outer part ofthe motor (using VOM).

- Check the supply

- Run the motor to check the value and direction

II/ CONTROLING UNIVERSAL MOTOR:

on UM speed control under variable loading conditions A mathematical model for

UM is designed Two controllers are proposed for controlling the motor speed, outputrate controller and output reset controller Ant Colony Optimization (ACO) isproposed for tuning the controller’s parameters due to its impact on solving differentoptimization problems It possesses fast convergence, minimum algorithmparameters required, lower consecution time and give optimal results withoutneeding large number of iterations The results are compared and discussedaccurately, which show the proposed tuning technique work well and give optimalresults for both controllers

2 Control Motor’s Speed:

a Centrifugal Mechanic

In the case where variable RPM (more than two desired settings for RPM)are required for universal motors, the centrifugal mechanism of RPM control is

The setting of RPM is made by a centrifugal switch located inside themotor as shown in the diagram below This centrifugal switch can be controlled

or adjusted by means of an external lever

If the motor speed rises above that set by the lever, the centrifugal device

or switch opens two contacts and inserts a resistance R in the power circuit tothe motor, which causes the motor speed to decrease

If the motor runs too slowly, the centrifugal device will close the twocontacts and short circuit the resistance so that the motor speed rises Thisprocess is repeated so rapidly that variations in speed are not noticeable

A resistance is connected across the centrifugal switch or device toperform this function A capacitor C is used across the contact points in order

to reduce sparking produced due to the opening and closing of these points.Moreover, it prevents pitting the of contacts

b Resistance Method:

In this method, the speed of the electric motor is controlled or set byconnecting a variable resistance R in series with the motor Due to having theresistance before the motor, the current to the motor is reduced, which in turnsreduces the speed of the motor according to the setting of that variableresistance This type of speed control is employed for motors used in sewing

machine

In this casethe amountof

resistance

motorpowercircuit canbe

changed

by means

of a footpedal Also, a universal motor in drink and food mixers uses this method to setthe speed and can be changed by setting the variable resistance

c Field Tapping Method: