Voltage equation of a motor the voltage v applied across the motor armature has to i overcome the back e. Check the source of power, overload, fuses, controls, etc. To achieve long motor life in wet environments, like a dairy processing plant, standard motor construction and standard water ingress protection are insufficient. Magnetic flux density relation between magnetic field intensity h and magnetic field density b measured in tesla. Dc machines quiz questions dc machine quiz questions. Simplified dc motor with an electromagnet as stator. The electric current may be classified into three main types. Maintenance and troubleshooting of electric motors reliance electric posted 11005 motor maintenance scheduled routine care introduction the key to minimizing motor problems is scheduled routine inspection and service. Typical inspections when troubleshooting dc motor problems or doing preventative maintenance. Eb v2 thus gross mechanical power developed by a motor is maximum when back e. Loadflow analysis in power systemsgalli, anthony w.
The dc motor should function fine if it works on the principle that as long as the 12 volts output from the converter is greater than the dc amp rating on the motor by over 30% to 50%. Spoke with a shop fellow who said he tested it on a like machine and it worked. Many dc motors use an electromagnet for the stator, as illustrated in figure 27. The flux of a dc motor can be changed by changing ish with help of a shunt field rheostat.
The flywheel is a rigid body rotating about its central axis. Voltage equation of a motor conditions for maximum power torq ue armature torque of a motor shaft torque speed ot a d. The core losses are 200 w, and the mechanical losses are 240 w at full load. Below is an overview of the most common problems and the fixes to get your drive and motor working properly. Dc machine multiple choice questions with solutions. A shunt generator delivers 450 a at 230 v and the resistance of the shunt field and armature are 50. This article presents a basic explanation of electric motor construction and. Power supply is an important consideration in the application of dc motors. Apr, 2017 this is part 3 of the training series on low voltage motor drives in appliances. Dc motors electrical engineering questions and answers. Wayne beaty third edition mcgrawhill new york san francisco washington, d.
Chapter 27 questions 1, 3, 5 chapter 27 problems 7, 19, 49 wileyplus assignment. For a dc motor rated at 742 amps, the current density of the brushes works out to 55 ampssq in. If the motor problems cant be resolved with this list, please contact your supplier for assistance. Dc motors, generators and energy conversion devices. A failed motor, then a failed drive have cause me no end of pain. Auckland bogota caracas lisbon london madrid mexico city milan. Differentiating both sides with respect to ia and equating the result to zero, we get d pmd ia v. The frequency of routine service varies widely between applications. Dc motors are rarely utilized in normal applications as a result of all electrical supply firms furnish electrical energy but, for special applications like in steel mills, mines and electric traction, its advantageous to convert ac into dc so as to use dc motors. Electric motor failures can be due to mechanical component failure or electrical circuit failure. Motor principle comparison of generator and motor action significance of the back e m. Induction motor equivalent circuit with seventh harmonic. Problems 4 1 a 230 v dc shunt motor runs at 800 rpm and takes armature current of 50 a.
We send in a pulse width modulated signal from port t3 which will drive the motor. So i hooked the motor to a new out the box dc drive, before connecting the motor checked output voltages, and were what i expected. In the find bar of the preflight window, type syntax. When driven at 750 revmin the machine produces a total armature current of 400 a. Have played around with various electrical things, no real electronics experience, and no education in this area. Dc motors although ac motors are used in most of the cases, dc motors have many applications and used for multipurpose applications. Refer to the wiring diagram to verify the motor is wired correctly. The conductors of the armature of a dc generator are connected to commutator segments. Dc motor principle a machine that converts dc power into mechanical energy is known as dc motor. Energize the motor and test the controls and overall system operation. Dc machines 1 dc machines transformsmechanicalenergyintoelectric energywithdc voltage and currentdc generatoror dynamo, or converselydc motor. It is a machine which convert electrical energy into mechanical energy. Torque and motor volume 23 specific output power importance of speed 23 energy conversion motional emf 25. With drives and motors, there are a few common problems that application engineers tend to see the most.
Dec 18, 2014 this is my first post here, and by intro i am a complete noob. Its operation is based on the principle that when a current carrying conductor is placed in a. The purpose of this supplement is to present the basic material needed to understand the operation of simple dc motors. If the armature current is ok, concentrate on mechanical problems associated with the brushes. Dc motor introduction, principle and working my tech info. When power for the stator electromagnet is supplied by a separate dc source, either. At fullload and rated voltage, the line current is 55a.
Determine if the problem is in the motor itself or in the driven equipment. Once youve corrected all identified problems and the motor is installed and aligned, youre almost done. Mechanical problems rather than electrical ones are usually the cause. Associate professor, electrical and computer engineering, university of missourirolla. Expression for torque in terms of the parameters concerned in this problem is as. It is surprising how often simply restarting your computer solves a problem. Problems 198 stardelta wyemesh starter 202 autotransformer starter 202. The principle of operation of a dc generator is similar to that of the ac generator, which was discussed previously. When current carrying conductor is placed in a magnetic field it experience. The armature circuit of the macbine bets a resistance of one fl. Basic linear model for dc motor with inertial load.
Dc motor introduction, principle and working introduction. Dc machines quiz questions electrician exams practice tests. First of all, measure the armature current with the dc ammeter to see if the motor is overloaded. Practicing all dc motors electrical engineering questions and answers in online helps you to improve your ability to attend the real time gate, ies and bsnl jto exams. This is part 3 of the training series on low voltage motor drives in appliances. To achieve long motor life in wet environments, like a dairy processing plant, standard motor construction and standard water. A script for this problem is appended, and the more precise answers printed out by that script are. Note before removing dc motor brushes always put the brush back in the same hole of the motor. Electric motor system diagnostics electric motor system diagnostics richard scott alltest pro, llc this session is eligible for 1 contact hour. Plant engineering tips for preventing dc motor problems. The most common way to provide dc voltage to a motor from an ac.
This is my first post here, and by intro i am a complete noob. Dc motor speed control problems all about circuits. Induction motors the single phase equivalent circuit of a threepha. This conversion of ac into dc is accomplished through the use of a commutator.
The primary advantage of the dc motor is that it can develop constant torque over a wide speed application. Now tbe machine is loadej so that it is driving a load torque of 100 nm. In the model, rs is the resistance of the cable leading to the motor. How to solve common electric motor problems and get great. Review questions the purpose of the following questions is to remind you of some fundamental topics and results that we derived in this class. In this training you will learn about power stage architectures, topologies, challenges and solutions for brushless dc motor drives. Motor and motor control troubleshooting techniques. State the term that applies to voltage variation from noload to fullload conditions and how it is expressed as a percentage. An example is a 35a bridge rectifier configured with a 120v power cord and test leads.
If the speed of a dc machine is doubled and the flux remains constant, the generated e. Dec 07, 2014 dc motor introduction, principle and working introduction. Can be used to indicate the value of dc and ac quantity. Motor motor characteristics characteristics of series motors. We used the fact that the speed of a dc motor is directly proportional to the voltage applied across its windings. Typical dc motor brushes and commutator brushes and. A rotating armature coil passes through a magnetic field that develops between the north and. They provide the most surface contact since they are worn in. Dc motor dc generator multiple choice questions with solutions. The brushless motor, unlike the dc brushed motor, has the permanent magnets glued on the rotor. Dc motor troubleshooting, inspection and learn to repair of dc motor brushes and commutators. Hence a problem would arise not with a case of excess volts dc vdc capability but in case of too little vdc.
For these hours to appear on your certificate, you must. This is intended to be used as the reference material for the linear and dc motors lectures in ee301, as this material is not covered in the text. Basic construction of modern pmmc can be seen in figure 1. The system shown in figure 1 is a linear model of the quanser srv02 dc motor with a static inertial load. Motor motor characteristics characteristics of series motors characteristics of.
Dc motors advantages and hazards of operating dc motors. To power the motor, the 2n2222 npn bjt was employed as a switch. That figure is in line with the current density rating of many carbon brush grades. When connected to a supply of vt 48v at standstill, the motor develops a torque of 1500nm. Tips for troubleshooting motor drives design world. Calculate the armature current at standstill and combined motor constant kc. Read chapters 26, 27 chapter 26 questions 1, 3, 10 chapter 26 problems 1, 17, 35, 77. Sep 25, 2015 dc machine multiple choice questions with solutions to prepare electrical exams like ies, gate etc. Possible causes could include a short on the motor output, grounding on the motor terminals, or an overloaded motor, among other causes. It consists of several copper segments, separated by insulation. Steady current dc current varying current alternating.
So please be gentle, and especially please use simplest terminology. Mechanical problems such as worn bearings or a broken pinion could cause a mechanical overload. Have your badge scanned at the door attend 90% of this presentation fill out the online evaluation for this session. The gross mechanical power developed by a motor is pm v ia. May 30, 2016 dc motor problems and solutions sumit maitra. Explain the effect of motor reaction in a dc generator. The stator of the motor is composed by the electromagnets, usually four of them, placed in a cross pattern with 90o angle between them.
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