Project Submission Report : REWINDING & SPEED MEASUREMENT OF A CAPACITOR-RUN SINGLE PHASE INDUCTION MOTOR PDF

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BANGLADESH UNIVERSITY OF ENGINEERING AND TECHNOLOGY EEE 206: Energy Conversion Laboratory Project Submission Report Name of the Project: REWINDING & SPEED MEASUREMENT OF A CAPACITOR-RUN SINGLE PHASE INDUCTION MOTOR Group No.-2 Submitted to- Dr. Abdul Hasib Chowdhury & Md. Hadiur Rahman Khan ...

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BANGLADESH UNIVERSITY OF ENGINEERING AND TECHNOLOGY EEE 206: Energy Conversion Laboratory

Project Submission Report

Name of the Project: REWINDING & SPEED MEASUREMENT OF A CAPACITOR-RUN SINGLE PHASE INDUCTION MOTOR Group No.-2 Submitted toDr. Abdul Hasib Chowdhury Professor Dept. of EEE BUET.

&

Md. Hadiur Rahman Khan Lecturer Dept. Of EEE BUET.

Submitted ByAtika Rahman Paddo

1506171

Mahmudur Rahman Pabel

1506172

Mushfiqul Abedin Khan

1506173

Mursalin Ibne Salehin

1506174

Khairul Haque

1506175

Joyantra Mitra

1506176 Date of Submission: 09.01.2018

Forwarding Letter January 09, 2018

Dr. Abdul Hasib Chowdhury, Md. Hadiur Rahman Khan Department of Electrical and Electronic Engineering Bangladesh University of Engineering & Technology

Subject: Forwarding letter for Project Submission Report of course no. EEE 206 (Energy Conversion Laboratory)

Sir, We belong to Group No-2 (C-2) in Energy Conversion Laboratory (EEE 206). As a part of this course, we were supposed to work on a project. On your consent we worked on the project named “Rewinding & Speed Measurement of a Capacitor-Run Single Phase Induction Motor”. Here is the complete project report with details of our work submitted. Yours faithfully,

Group No.

02

Student ID: 1506171 1506172 1506173 1506174 1506175 1506176 Section: C-2 Department: Electrical and Electronic Engineering Level/Term: 2/2

Index Contents 1. Objective 2. Introduction 3. Theory 4. Apparatus & Components 5. Working Procedure 6. Speed Measurement 7. Result 8. Complications 9. Summery 10. Discussion

Page No. 1 1 2 4 4 9 12 12 12 13

Name of the Project: REWINDING & SPEED MEASUREMENT OF A CAPACITOR-RUN SINGLE PHASE INDUCTION MOTOR

Objective: The idea of this project was to rewind a motor (which can be any induction motor), it can be an old or new one, so that the motor functions properly with a good measurement of running speed. Basically the objective of this project was to1. Getting to know about different parts of a motor by opening an aged motor part by part 2. Knowing about the slot system of a motor 3. Getting to know about the winding i.e. the coils and how to make them 4. Unwinding of a motor 5. Rewind a motor with our own-made new coils 6. Connecting the parts (stator and rotor) after winding is done and running the motor by connecting with specific power supply 7. Measuring the speed of the motor

Introduction: The motor which was used in this project was a capacitor-run single phase induction motor. We already know that single phase induction motor is not self-starting because the magnetic field produced is not rotating type. In order to produce rotating magnetic field there must be some phase difference. In case of split phase induction motor we use resistance for creating phase difference but here we use capacitor for this purpose. We are familiar with this fact that the current flowing through the capacitor leads the voltage. So, in capacitor start inductor motor and capacitor start capacitor run induction motor we are using two winding, the main winding and the starting winding or the auxiliary winding. With starting winding we connect a capacitor so the current flowing in the capacitor i.e Ist leads the applied voltage by some angle, φst. The running winding is inductive in nature so, the current flowing in running winding lags behind applied voltage by an angle, φm. Now there occur large phase angle differences between these two currents which produce a resultant current, I and this will produce a rotating magnetic field. Since the torque produced by these motors depends upon the phase angle difference, which is almost 90o. So, these motors produce very high starting torque. In case of capacitor start induction motor, the centrifugal switch is provided so as to disconnect the starting winding when the motor attains a speed up to 75 to 80% of the synchronous speed but in case of capacitor start capacitors run induction motor there is no centrifugal switch so, the capacitor remains in the circuit and helps to improve the power factor and the running conditions of single phase induction motor.

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Theory: Single-phase motors do not have a unique rotating magnetic field like multi-phase motors. The field alternates (reverses polarity) between pole pairs and can be viewed as two fields rotating in opposite directions. They require a secondary magnetic field that causes the rotor to move in a specific direction. After starting, the alternating stator field is in relative rotation with the rotor. A variation of the capacitor-start capacitor-run motor is to start the motor with a relatively large capacitor for high starting torque, but leave a smaller value capacitor in place after starting to improve running characteristics while not drawing excessive current. The additional complexity of the capacitor-run motor is justified for larger size motors.

Capacitor-run motor induction motor.

A motor starting capacitor may be a double-anode non-polar electrolytic capacitor which could be two + to + (or - to -) series connected polarized electrolytic capacitors. Such AC rated electrolytic capacitors have such high losses that they can only be used for intermittent duty (1 second on, 60 seconds off) like motor starting. A capacitor for motor running must not be of electrolytic construction, but a lower loss polymer type.

Capacitor-Run Motors: Capacitor-Run Motors are technically referred to as "Permanent-Split Capacitor (PSC) Motors" in most manufacturers' literature. Generally available sizes of capacitor run (PSC) motors range from fractional sizes up to 5-horsepower with most being less than 3-horsepower. They come in a wide variety of synchronous speeds. The speed of this motor varies about 10% from no-load to fully loaded conditions. Capacitor-run motors are available as multi-speed motors with two, three, or even four fixed operating speeds when appropriate control equipment is used.

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Torque-Speed Characteristics: A capacitor-run motor has lower starting-torque (50%-to-100% of full-load torque) than most other single-phase motors with the exception of the shaded-pole motor. The capacitor in this motor must be sized as a compromise between good starting and good running characteristics. They provide lower starting-torque but better running characteristics than splitphase motors. These are used in instances where low-starting torque is needed (i.e. centrifugal pumps, fans, compressors and some conveyors). They are very common as condensing unit fans on air-conditioning systems. Capacitor run motors make good replacements for shaded-pole motors. In this role they are more-efficient and require lower-current levels than shaded-pole motors. For these reasons they are effective in fans with low-starting-torque requirements.

Relative Costs: Capacitor-run motors typically cost from 90% to 100% of the cost of a comparable 3Phase Induction Motor. They also cost less than similar single-phase motors containing both a capacitor and switching system in the starting windings.

Operation: The equivalent winding in this motor is referred to as a "Capacitor Winding." Capacitorrun motors are similar to split-phase motors except they replace the centrifugal switch with a capacitor commonly referred to as a running capacitor. The capacitor within the capacitor winding of the capacitor-run motor remains functional throughout starting and operation of the motor. The capacitor improves both starting and running torque compared to a shaded-pole motor. Since there is no switch in the capacitor winding of this motor, the current in the winding is not switched off during motor operation. In normal split-phase motors, this current is turned off after starting. The motor will have starting problems if the capacitor fails or discharges from lack of use. Run capacitors are designed for continuous duty while the motor is powered, which is why electrolytic capacitors are avoided, and low-loss polymer capacitors are used. Run capacitors are mostly polypropylene film capacitors and are energized the entire time the motor is running. Run capacitors are rated in a range of 1.5 to 100 µF, with voltage classifications of 370 V or 440 V. If a wrong capacitance value is installed, it will cause an uneven magnetic field around the rotor. This causes the rotor to hesitate at the uneven spots, resulting in irregular rotation, especially under load. This hesitation can cause the motor to become noisy, increase energy consumption, cause performance to drop and the motor to overheat.

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Windings: Windings are wires that are laid in coils, usually wrapped around a laminated soft iron magnetic core so as to form magnetic poles when energized with current. Electric machines come in two basic magnet field pole configurations: salient-pole machine and nonsalient-pole machine. In the salient-pole machine the pole's magnetic field is produced by a winding wound around the pole below the pole face. In the nonsalient-pole, or distributed field, or round-rotor, machine, the winding is distributed in pole face slots.[55] A shaded-pole motor has a winding around part of the pole that delays the phase of the magnetic field for that pole. Some motors have conductors that consist of thicker metal, such as bars or sheets of metal, usually copper, although sometimes aluminum is used. These are usually powered by electromagnetic induction.

Apparatus & Components: Following apparatus & components were used in completion of our project. 1. 2. 3. 4. 5. 6.

An aged capacitor-run single phase induction motor 28 number (local) copper wire for winding Forma to make winding with adjustable size Special fiber paper for insulation Cotton cloth for insulation Basic tools for opening/dissemble the motor such as screwdrivers, hammers, wrenches, blades 7. Pen, pencil, clip, pins 8. Spray Lubricant such as varnishing materials (drying oils, resin).

Working Procedure: Single phase motor usually has two coils, main with bigger resistance (generating a pulsating magnetic field) and auxiliary with smaller resistance (gives motor a direction of rotation). There must be a capacitor on the motor. Its value is different for different electric engines (for smaller electric engines around 20 uF-100uF). 2 capacitor can be on motor, "run" capacitor (always connected, lower value capacitor) and "Start" capacitor (connected with centrifugal switch, higher value capacitor) Following steps were done in rewinding the single phase electric motor.

1. Disassembling Motor The screws securing the cover were unscrewed and the cover of motor was removed first. After opening the cover, the previous windings was bound but not in good shape, probably burned out which is why the aged motor was not in running condition at first. The front cover with rotor was 4|Page

gently removed out of the main housing of the motor. The motor hadn’t any capacitor attached with it.

2. Motor Inscription Board The motor’s inscription board was checked where the rated values were given with other information.

Fig.: Motor Inscription Board

3. Examining the stator slots The stator slots were thoroughly checked and we found total 24 slots with the windings. The slots were basically the gaps in the stator. Each of coil was placed in 2 slots. It was checked how many coils were placed in the slots in which position. It was noted down for future rewinding process.

4. Counting the wire number in a single coil The total wire number was counted in a single coil so that we could make the coils with same number of wires. It was found that the main coils had around 160 (±2) wires in each and the auxiliary coils had around 130 (±2) wires in each.

5. Coil arrangement in the stator slots The coils were in two kinds. Main coils and auxiliary coils. 8 coils were in series and 6 of them were in parallel connections. The main wires were of 28 local number copper wire.

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6. Cut of Winding The windings were cut with the help of hammer, sometimes we pull the windings out in free hand also. After cutting the first few windings, other windings were pulled out easily.

7. Cleaning the slots After the pulling the old windings out, the slots were cleaned. The previous insulation papers were pulled out and the slots were cleaned with a screwdriver without damaging the stator.

8. Inserting Insulating Paper After the slot gaps were cleaned, insulated paper was inserted in there before we put the windings.

9. Making the windings The windings of different sizes were made with the help of a wood-forma. The wires were turned in specific numbers so that we get equal sizes of all windings. The coil making image with the forma is given here.

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10. Placing Coils in stator The coils were carefully placed in stator. The coils were rotate coils so their end wires came out on the side, where was the hole from stator to electrical clips. Sometimes sharp object such as pen was used to insert the coils. Then they were connected to electrical clips. The images of placing the coils are given below.

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11. Binding the coils Finally the coils/windings were bond with thread or thin cotton cloth.

12. Varnishing Varnish lacquer (Spray lubricants) was spilled on the motor’s inside for better connectivity.

13. Connecting capacitor The capacitor was connected with leading wire after the winding was done.

14. Covering the stator The rotor was placed and screwed tightly for giving connection to check whether the motor runs or not.

Fig.: The capacitor-run motor after the rewinding is done

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Speed Measurement: The motor’s speed was measured through an audio editing software ‘Audacity’. We had run the motor which ran successfully and a card-paper was attached with the motor’s shaft. The cardboard was placed near a surface so that each time the shaft rotates we get a sound. While the motor was running, we recorded the sound created by the shaft and the sound was analyzed through the software. The sound wave-shape of the shaft was observed closed through the software. As the soundwave expresses the rotation of the shaft, the time between two peak point of the wave determines the time of one rotation. We found out the time from the software and the we got the time of one rotation. Thus we calculated the speed.

A card paper is attached with the rotor shaft

The sound of the motor is recording

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The recorded audio is observed in the ‘Audacity’ software as sound wave and zoomed to the point where two peak points of the wave can be seen.

Fig.: The sound wave shape in software’s view

Fig.: The sound wave in zoom mode 10 | P a g e

The time between two peak points (Time duration of 1 rotation of the rotor) is gotten from the software.

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Thus the synchronous speed is, n= 60/0.041=1463 rpm

Result: The motor was given 220V line voltage connection and it has run successfully with an effective speed. The speed was measured afterwards and was found to be around 1463 rpm.

Complications: The following complication were faced during the implementation and working on the project. 1. The space inside a slot was quite small and we had to put a whole coil inside it which needed quite effort and time. Moreover, the last number of turns were difficult to put through, so we sharpened a pen and pen-clips and pushed the coils inside which worked fortunately. 2. While using the 'forma' (the device to make coils of wires), sometimes the turns were being loosen. So we had to try more than once to make a single coil. 3. The number of turns were not exactly same in each coils. There might ±2 number of turns. 4. As the coils filled up all the spaces of the slots, it was hard enough to put insulations inside it. 5. It needed a lot of time and effort to cut the insulation papers in the right measurement.

Summary: Our project was to rewind the coils of a single phase induction motor which was not working previously and return its rotation per minute to the rated value. In order to do that, we bought a non-working induction motor whose core was okay. Then we brought out the coils inside it, observed the slots and studied about it. After that we started the main work of the project, which is the winding. We needed wire number 28, almost half kg of them. We put coils inside the twenty four slots in according to number and insulated them with special insulation papers. After those works, the motor ran nicely and we measured its rpm. To do that we used a software named ‘Audacity’ which gave us the speed of the motor which is around 1463 rpm.

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Discussion: 1. The project was all about rewinding an aged motor to make it work and speeding up to the rated value. Although the main process was about winding, many facts came up according the working procedure of a capacitor-run single phase induction motor. First of all, the winding of the motor was a time consuming process but totally unpredictable of whether the project will be successful or not. The process was done under supervision of our course teacher and lab assistant teacher. 2. Due to the unavailability of a three phase induction motor of larger size and affordable price, the project was started with a capacitor-run single phase induction motor. 3. The study of the slot system and coil arrangement was learnt from an expert electrician from a local electric shop. 4. Before we got started with the rewinding process, we tried to run the motor by giving exact voltage connection from line voltage supply. But unfortunately the motor did not run which made it sure that the motor was quite an aged one. 5. The stator had 24 slots for winding. Eight slots were filled up with auxiliary winding and rest of them were filled up with main winding. The objective of auxiliary winding is to start up the device. But the motor can also start without help of the auxiliary winding. In that case, we needed to start the motor by any external source. A capacitor was used in this motor. With the help of this capacitor the auxiliary winding started the motor. 6. In auxiliary winding, around 128-130 turns per coil were made whereas in main winding we took 155-160 turns per coil. 7. It was studied that if more wires are used in a single coils, the motor could carry out more load. On the other hand, if less coils are use, the motor could carry small load. Due to the complexity of inserting more wires in the slot gaps, we kept our number of turns in a single coil constant for all the windings. 8. During the making of coils by the help of a wooden forma from copper wires, it was tried to maintain same weight of before but the weight can be different a bit. Considering it negligible, we continued the winding process. 9. The coils (both of series and parallel connections) were placed with the stator slot properly by hand and sometimes with the help of pencil, pens, clips and pins. 10. The windings were closely attached with other coils, so it was necessary to insulate them from each other. So we used cotton clothes and sometimes special thread (provided by a electric shop) to bind them properly so that they don’t get shorted with each other, which could result into short connection and the motor might not run at all.

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11. As our target was to get the rated value of speed, we needed to make sure to give input supply of rated voltage, which is why the motor was given connection with only 220V, never more or less voltage. 12. For the speed measurement of the motor’s shaft, diff...