UNIVERSAL MOTOR VELLORE INSTITUTE OF TECHNOLOGY Presented by: GROUP 10 group members PRIYANSH SAXENA - 21BCY10096 PRAKHAR SINGHANIA - 21BCY10111 UDEESHA UDI - 21BCY10027 GOURI NANDANA - 21BCY10029 AKSH RAIZADA - 21BCY10023 SIDDHARTH DAYAL - 21BCY10019 RABJOT SINGH KERKETTA - 21BCY10045 Table of content What is universal motor? Types of motor. (similarities and differences). Properties of universal motor. Construction & working. Applications. Advantages & disadvantages. Universal motor life. is an electric motor capable of working on either direct current or single-phase alternating current at approximately the same speed and output. Its major applications are electric vacuum cleaners, power tools, and juicers. The armature windings and both field windings are in series Mostly found in hand drills, mixers anything that needs a variable speed and low cost. The two magnetic fields are produced by voltage Motor can reverse its rotating direction by changing the armature winding or the field windings input and output polarity's but not both. Voltage and current are applied directly to the armature windings through the brushes. This type of motor is a quite motor and is good for heavy duty loads. Two capacitors are connected in parallel but are also connected to the start winding in series. TYPES OF MOTORS TYPES OF MOTORS NON-COMPENSATED MOTORS This motor is usually built with concentrated or salient poles COMPENSATED MOTORS This motor has a distributed field windings(main field and copensating winding) NONCOMPENSATED COMPENSATED SIMILARITIES Both the types of motors develop unidirectional torque regardless of the supply with which they run. The supply may be AC or DC but the direction of torque is same. The direction of rotation can be changed. For the noncompensated motor , the direction of rotation can be reversed by changing the direction of flow of current through the armature or field winding. In case of compensated type motor, either the armature leads or the field leads and shifting the brushes against the direction of rotation of motor. This helps in reversal of rotation. DIFFERENCES NON COPENSATED COMPENSATED They run at high speed. They have high starting torque. Compact size and are lightweight. They are noisy because of the commutator and brushes. Not all series wound motors operate well on AC current.If an ordinary series wound DC motor were connected to an AC supply, it would run very poorly. The universal motor is modified in several ways to allow for proper AC supply operation. There is a compensating winding typically added, along with laminated pole pieces, as opposed to the solid pole pieces found in DC motors. A universal motor's armature typically has far more coils and plates than a DC motor, and hence fewer windings per coil. This reduces the inductance. Speed/Load Characteristics Speed/load characteristics of a universal motor is similar to that of DC series motor. The speed of a universal motor is low at full load and very high at no load. Usually, gears trains are used to get the required speed on required load. The speed/load characteristics are (for both AC as well as DC supply). Construction 1. Stator Core 2. Stator Winding 3. Rotor 4. Commutator 5. Brushes 6. Shaft It consists of a stator on which field poles are mounted. Field coils 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 which induce while operating on AC.) The rotary armature is of wound type having straight or skewed slots and commutator with brushes resting on it. The commutation on AC is poorer than that for DC because of the current induced in the armature coils. (For that reason brushes used are having high resistance.) By way of carbon brushes, the stator windings are connected in series with windings in the rotor. In the universal generator, the condition is remarkably different. Stator windings and rotor windings are used in a universal engine. The current in the rotor windings, as in the induction motor, is not purely the product of inductive coupling. About its construction, the distinguishing characteristic of the universal motor is that the stator and rotor windings are wired in order. (This helps to create a voltage gap between them so that the rotor can pursue the rotating magnetic field of the stator ). The current is channeled by brushes into the rotor. Working Principle The working principle of the universal motor is like a DC series generator. When the current flows into the field winding, it generates an electric field. The same current is still emanating from the armature conductors. When a current conductor is put in an electric field, a mechanical force is encountered. Owing to this magnetic force, the rotor is beginning to spin. The position of this force is provided by the Lefthand rule of Fleming. Force on conductor, F=I(LxB) where I is the current flowing through the windings and L is active length of conductor. Mechanism When a DC voltage is applied to the motor, the same current flows through the stator and rotor coils. The magnetic fields around the winding interact and develop torque to turn the rotor. The direction it turns is determined by the direction the current flows through both sets of windings. When an AC voltage is applied, the direction of the current will alternate. Since the current reverses in both the rotor and stator at the same time, the magnetic fields around both windings also change simultaneously. The result is that the interaction of the two fields causes the In universal Motor both the armature winding and field winding direction of the developed torque to remain the same. is connected in series. Therefore, the rotor turns one way, regardless of which direction the applied current flows. Reference : www.LearnEngineering.org APPLICATIONS OF UNIVERSAL MOTOR Universal motors are used in applications where high and good speed control is necessary, due to the simple structure, small size snd portability of universal motor. Their high speed and light weight makes them useful for various basic appliances such as: Sewing machine, Table fans, Hair dryers, Grinders, Drink mixers etc. The stronger motors are used in: Portable drills, Blenders and Vacuum cleaners The electronic speed control of Universal motor is an ideal choice for domestic washing machines. It can be used to spin the drum in both directions, It can also be run up to the high speeds required for the spin cycle. APPLICATIONS OF UNIVERSAL MOTOR Most important application includes- starters of combustion engines which are usually universal motors, with the advantage of being small and having high torque at low speed, they are a good choice for performing the function. The on-vehicle mounted electric winch of the vehicles also use universal motor. Basically, this machine has helped in both domestic and commercial spaces to simplify the tasks in every field. Advantages Universal motors are less costly due to their simple construction and no requirement for permanent magnets. Universal motors provide good torque at low speeds. They can rotate at high speed due to the connection of armature windings and field windings in series. Due to its small size and less weight of the universal motor, it is most preferable in many applications. Eddy current losses are reduced due to the presence of an electromagnetic field and heating is avoided. Universal motors require low power input to run the motor. These motors have the capability to run at any given availability speed. Disadvantages Universal motors produce relatively higher noise and this noise increases with the speed of the motor. There are high chances of vibrations and these vibrations may damage the motor. There is no possibility to run the motor in opposite direction. These motors caused overheating. Universal motors require frequent maintenance due to brushes and commutators wear out very quickly. UNIVERSAL MOTOR LIFE Universal motors generally, do not have long operating lives. A typical appliance motor requires brush replacement after 200 to 1200 hours of service. The time it takes to accumulate this much service depends on the kind of appliance and on how it is used. An appliance used infrequently and for short periods of time may take 15 to 25 years to accumulate 200 to 1200 hours of service. An appliance operated constantly will take only 8 to 48 days to accumulate the same number of hours of service. A larger and more expensive universal motor may be able to run for 3000 to 5000 service hours before, the brushes must be replaced. THANK YOU !!
