induction motor with a rated current of 57.8 A. spins a mechanical load at 1778 RPM. Overloads = name plate full load current times either 115% or 125% depending on S.F. Motor Formulas V = Volts A = Amperes R = Ohms P = Watts PF = Power factor (Motor) Eff = Efficiency (Motor) HP = Horsepower BHP = Break Horsepower (Motor) r = running np = nameplate Max. Let . Since the load is running at rated motor speed
The induction motor mainly divided in to two parts. X ExsistingEstimatedBHP Max.BHP 3 Ohm's Law: V=AR R V A = A V R = Single Phase: P=V A PF So, the selection should be made between the rated speed and the synchronous speed. 2. than a 3-phase induction motor of the same frame size, it is less efficient and it operates at lower power factor. induction motor has been an industry workhorse for electro-mechanical conversion for over 100 years. Determine the motor parameters and the total core, friction and windage losses. Load test on three phase induction motor. Let a single phase a.c. source be The motor parameters given in ohms refered to the stator are: R 1 = 0.18 R 2 = 0.20 X 1 = 1.15 X 2 = 1.23 X M = 40 R fe = 317 Total mechanical power losses (friction, windage and stray) are 170 W Find: a.)
It is also stationary part of the induction motor. the starting current when For calculations involving starting values, the rotor is assumed to be stationary so that s = 1. The magnitude of rotor current in 4.
Consider a single phase induction motor whose rotor is at rest. Regenerative test on dc shunt machines. We are looking for the smallest heater/overload size allowed for motor #2 on motor diagram #1. Three-phase induction motors are also called asynchronous motors. But induction motors were used only for applications requiring constant speed. AC Motor::: An AC motor is an electric motor driven by an alternating current (AC). Measure the voltage and power to the phase. The input impedance seen by the source V1 Motor Slip. In the above circuit, the calculation of rotor current is greatly simplified . LOCKED ROTOR TEST The locked rotor test, like short circuit test on a transformer, provides the information about leakage impedances and rotor resistance. The full load is usually varies between 0.82 and 0.93. Induction Motor Equations ENGN1931F Spring 2019 . e For convenience we assumeat 0, 0 and =0t that t = = and therefore PEAK = = L R S tt t. The flux in the single-turn coil on the rotor surface is At time of starting, the voltage induced in the induction motor rotor is maximum because slip is maximum (S = 1). Used to control the speed of rotor. Induction motors are extensively used in marine environments for pumps, First Example: Constant speed operation at rated speed but with variable torque eg Induction motor running at constant speed. The They are the most commonly used electric machines. The most widespread version of this law states that the induced electromotive force in any closed circuit is equal to the rate of change of the magnetic flux enclosed by the circuit: E = d B d t {displaystyle {mathcal {E}}=- { {dPhi _ {mathrm {B} }} over dt} } , where. E {displaystyle {mathcal {E}}} (b) the resulting equivalent circuit. cause damage to induction motors unless they are properly designed and built. 3-Phase Induction Motor (Power Calculations) 1- A 20hp, 3-phase, 500 V, 50 Hz, induction motor with 6 poles runs at 950 rpm with power factor of 0.86 lagging. 7. A set of typical arrangements is shown below: Figure 1: Induction motor with stator and rotor (1) Figure 2: Distributed winding inside stator Figure 3: Rotor of induction motor with slip-rings (2) The parameters of the motor equivalent diagram are established from fig-ure 1, using [2] or [5]. A 3-phase, Y connected, 460 volt (line to line), 25 horsepower, 60 Hz, 8 pole induction motor has the following constants, in ohms per phase referred to the stator: R1 = 0.342 X1 = 0.561 Z1 = 0.342 + j0.561 R2 = 0.164 X2 = 0.265 Types of AC Motor::: [depending on the type of rotor used] 1. Induction Motor Slip Calculator Slip speed is the speed difference between the Synchronous speed and Rotor speed. Slip speed = Synchronous speed Rotor speed = Ns -N . Since Retardation test on dc shunt motor. So, the selection should be made between the rated speed and the synchronous speed. Calculate its slip. The locked -rotor test is made at 15 Hz to minimize the errors due to saturation and skin effects. 2. 50 Hz, 3 phase induction motor runs at 960 rpm when the torque on the shaft is 200 N.m. Solution: Rotor speed = m = 1200 r/min. However, the reader The part of rotating magnetic field which reacts with rotor and is responsible to produce induced e.m.f. Maximum efficiency occurs at in rotor. Specific emphasis will be given to pump applications. Mining applications (hoists, trains, conveyors, etc.) LR S and be the angular velocities of the magnetic field (line frequency), rotor, and slip rspectively. Speed control of dc shunt motor by armature and field control. The motor operating regime is calculated as follows: a. Standard AC Motors The speed of Induction Motors and Reversible Motors vary with the size of the load torque. One 208 Volt, 0.75 HP, 3-phase induction motor . Pole changing 2. This is because there must be an air gap in an induction motor, which greatly increases the reluctance of the flux path and thus reduces the coupling between primary and secondary windings. The above expression for rotor current can be squared and substituted into the torque equation . 6. No load and Blocked rotor test on three phase induction motor to draw (i) equivalent circuit and (ii) circle diagram. This paper presents the starting time calculation for a squirrel cage induction motor. are somewhat similar. For this example, refer to the motor equivalent circuit and calculations described above. or KW as shown already, ns is the given specification. Example With Calculations. 25 How does the external resistance of slip-ring induction motor influence the motor performance. What is the minimum size overloads required for motor #2 on motor diagram #1 ? Swinburne's Test on dc motor. Rotor is at the stand still, while low voltage is applied to stator windings to circulate rated current. The stator or the stationary part consists of three phase winding held in place in the slots of a laminated steel core which is enclosed and supported by a cast iron or a steel frame as shown in Fig: 3.1(a). induction motor has the following equivalent circuit parameters: Rw1 = 0.25S Rw2N = 0.2S Xl1 = Xl2N = 0.5S Xm1 = 30S The rotational losses are 1700W. It usually contains the primary winding. SPEED CONTROL OF INDUCTION MOTORS The speed of an induction motor is given as N = 120f/p (1-S). External resistance connected to slip-ring and 1. Ans : Slip = 0.04 and fr = 2Hz 2. In this chapter, the development of the model of a three-phase induction motor is examined starting with how the induction motor operates.
To make this calculation, its generally best to ap- The importance of starting time lies in determining the duration of Totally enclosed induction motors are fit for such demanding applications (Figure 1.11). The first type is the induction motor or asynchronous motor: 3.In case of single phase induction motors, the stator winding Less slots: 1)less cost 2) less space lost due to insulation and slot opening; More slots: 1) smaller leakage inductance and larger breakdown torque 2) small MMF harmonics 3) better cooling Typically, stator teeth width between and 1, ratio of slot This energy is Conversion to mechanical power by motors (pumps, fans, HVAC, refrigeration compressors, power CALCULATION OF MAIN DIMENSIONS The output equation can be written as [1.11 ( )(10 )]D232 KVA K B ac Ln wav s KVA is obtained from H.P. Motor operated at rated voltage and no load. Motor calculation steps: The following steps adhere to article 430 of the NEC. One dynamometer with torque controller .
b. Example: Input Power Calculation An existing motor is identified as a 40-hp, 1800 rpm unit with an open drip-proof enclosure. Select number of stator slots 5. Also induction motors are able to operate in dirty and explosive environments. 5. Starting methods of Induction motor include: Direct On line (DOL) starters for less than 10 Kw motors. StarDelta starters for large motors. The stator winding is initially connected in a star configuration and later on changed over to a Delta connection, when the motor reaches rated speed. Auto transformer. We normally assume full pitched winding thus Kw = 0.966. One single-phase wattmeter plus miscellaneous apparatus as needed . This tutorial will introduce the user to the fundamental electrical and mechanical principles of AC electric induction motor design and application. 1.5 WORKING OF SINGLE-PHASE INDUCTION MOTOR: A single phase induction motor is inherently not self-staring can be shown easily. Initial Data . 11. Draw the approximate equivalent circuit for the motor Lock-rotor No-load DC Test V line = 36.2 V 460.0 V V dc Stator: The part of an AC induction motor's magnetic structure, which does not rotate. INTRODUCTION 2 . 3-Phase Induction Motors EE 340 . The steps cover motor full load currents, branch circuit General Electric squirrel cage induction motor Rated at: 5 HP 3-phase motor with SF 1.15 230/460 V 12.4/6.2 Amp nameplate current. Increases the starting torque 2. Once again, a sample table for motor 1624E009S is shown in Table 1. and a sample curve in Graph 1. Consider a three-phase 440 V, 50 Hz, six-pole induction motor. ASICS OFB INDUCTION MOTOR The basic operation of induction motor is similar to transformer, where the stator acts as the primary side of transformer and the rotor as secondary of transformer as shown in figure 1. Select number of stator slots and suitable three phase winding layout (experience). Determining the Operating Regime of the Induction Motors Determination of the induction motors operating regimes is done on each cal-culation iteration of the system load flow. The efficiency of the motor is a ratio of the real output power kWdivided by the real input power kW multiplied by 100%. 1. For a single phase induction motor the input power is equal to ( current multiplied by voltage multiplied by the power fact 3. m = Mechanical shaft speed. current and the applied voltage is the power input to the motor. The more ac-curately this can be calculated, the better. Check that the Motor can start the load and get it up to speed. If the stator losses are 1500 W and friction and windage losses are 500 W, find: Assume stator losses of 1 kW and friction and windage loss of 1.5 kW. Yoke is outer & stationary part, similarly the outer portion of the induction motor is known as stator.
3. What is the minimum size overloads required for motor #2 on motor diagram #1 ? Record all nameplate information for the induction motor. and complete calculations are shown below. Induction Motor Testing The No-Load Test: to obtain the rotational losses and information leading to magnetizing reactance. A 3hp, three phase, 4-pole, 400V, 50Hz, induction motor runs at 1440rpm. (1) Stator (2) Rotor In case of D. C. Motor basically it is divided into two main parts (i) Yoke (ii) Armature. calculation and MATLAB result of motor starting time [3]. The induction motor stator resembles the stator of a revolving field, three phase alternator. Motor sheave = Existing Motor sheave Dia. Where does the power go? Where sync = 120 * 50 / 4 = 1500 r/min. The synchronous speed of an induction motor depends on the frequency of the power supply and on the number of poles for which the motor is wound. the motor Calculate the speed of motor. An Induction motor has basically two parts Stator and Rotor . The transformation theory, which simplifies the analysis of the induction motor, is discussed. The slope of the induction motors mmf-flux curve is much shallower than the curve of a good transformer. To determine the percentage slip, rotor copper loss, rotor output, and efficiency of the motor, perform the following function: Standard AC Motors The speed of Induction Motors and Reversible Motors vary with the size of the load torque. Calculation: The rotor speed of a 4 pole induction motor at 50 Hz is 1200 r/min. 8. Decreases the starting current 3. One Phase Sequence Indicator . 3. Example 1: A 460 -V, 25-hp, 60-Hz, four-pole, Y-connected wound-rotor induction motor has the following speed motors. Basics of Induction Motor The basic operation of induction motor is similar to transformer, where the stator acts as the primary side of transformer and the rotor as secondary of transformer as shown in Figure 1. At each point selected for calculation, the efficiency of the motor is the mechanical power output divided by the electrical power input. The electric energy generated purchased by consumers for different needs. The motor takes 50 kW at 960 rpm for a certain load. The frequency of rotor induced EMF of 400V, three phase, six pole induction motor is 2Hz. Slip of a motor can be found from the formula: s = ( sync - m )/ sync * 100. sync = Speed of magnetic field. II. Determine (a.) the rated motor torque (power) and ideally greater than 75% of rated motor torque (power). Because of the above said advantages, induction motors are predominantly used in many industrial applications. The derivation of the dynamic equations, describing the motor is explained. (a) test circuit. The calculations are demonstrated on a numerical example. So obviously the speed of an induction motor can be controlled by varying any of three factors namely supply frequency f, number of pole P or slip S. The main methods employed for speed control of induction motors are as follows: 1. have the right motor for your application HOW TO SIZE A MOTOR 2 ANSWERS Load inertia The number one calculation to make when sizing a motor for a rotary application is the calculation of the load inertia. 28 Figure 6-53 The no-load test of an induction motor. 3-Phase Induction Motors 21 b. Squirrel Cage Motors 22 c. Wound Rotor Induction Motor 25 d. Single Phase Induction Motors 27 e. Split Phase Motors 30 f. Capacitor Motors 31 such as calculation of torque and horsepower. Induction Motors: Construction, Principle of Operation, Power and Torque Calculations, Characteristics and Speed Control June 2020 DOI: 10.13140/RG.2.2.15490.71360 3-phase induction motor formulas pdf The torque produced in the induction motor depends on the following factors :1. Calculate slip and frequency of rotor-induced EMF?