power systems loss

What is the importance of vibration analysis in electric motors? Vibration characteristics and balancing Vibration is defined as a mechanical fluctuation from an equilibrium point. Vibration can also be considered as period vibration. Period vibration is a random vibration or pendulum motion of an object. An example of this is the movement of tires when moving on a gravel road.

What are the typical losses that occurs in electric motor operations? Energy losses in electric motors fall into four categories: Power losses (Stator and Rotor Losses) Magnetic core losses Friction and windage losses, and Stray load losses.

SPEED CONTROL FOR ELECTRIC MOTOR TUTORIAL GUIDE How to control the speed of an electric motor? The relationship between rotational speed, supply frequency, number of poles and slip for induction motors is usually written: n = (2/p) x f x 60 x (1-s) Where: n = speed, r/min             f = frequency, hertz             p = number of poles             s = slip

ELECTRIC MOTOR BRAKING METHODS TUTORIALS What are the methods in stoppng/braking an electric motor? MECHANICAL BRAKING Mechanical braking with magnetic lifting is the technique most widely used for the braking of electric motors . At standstill brakes of this type provide a holding torque, and are therefore used where loss of braking in the event of power failure could be dangerous. However, in certain cases it may be necessary to lift the brake without starting the motor. This can be done by supplying the brake coil from a separate power source, or with a manual release device. The mechanical brakes used for electric motors are shoe, multiple-plate or disc brakes. ABB Motors brakes are disc brakes with asbestos-free brake pads or linings. During braking , the braking torque is constant with mechanical braking . At standstill the brake has a holding torque. On some brakes the braking torque can be reduced for softer deceleration. When the motor is started again, the holdin

TYPES OF FUSES FOR ELECTRIC MOTORS PROTECTION Different types of fuses for electric motor protection Fuses are over-current protective devices that are placed in an electrical circuit to protect the control components, wiring, insulation, and motor from damage caused by excessive current and associated heat. Overcurrents are considered any increase in continuous current above the normal operating current level. In motor circuits, overcurrents are classified in two different categories. Motor overloads are any overcurrents up to or slightly above locked rotor current (6-8 times FLA). This range of overcurrent is protected by overload relay protection devices which will be discussed in more detail later. Short-circuit overcurrents are those produced by short-circuit or ground fault conditions with fault current levels in excess of 8 times FLA. In today’s industrial facilities, short-circuit overcurrents can easily reach 50,000A. If the short-circuit overcurrents are not interrupted

ELECTRIC MOTOR SHORT CIRCUIT PROTECTION OVERVIEW How are electric motors protcted from short circuits? A short circuit is a direct contact between two points of different electric potential: 1. Alternating current: phase-to-phase contact, phase-to-neutral contact, phase-to-ground contact or contact between windings in a phase. 2. Direct current: contact between two poles or between the ground and the pole insulated from it. This can have a number of causes: damage to the varnish insulating the conductors, loose, broken or stripped wires or cables, metal foreign bodies, conducting deposits (dust, moisture, etc.), seepage of water or other conducting fluids, wrong wiring in assembly or maintenance. A short circuit results in a sudden surge of current which can reach several hundred times the working current within milliseconds. A short circuit can have devastating effects and severely damage equipment. It is typified by two phenomena. A thermal phenomenon A thermal phenomenon co

BASICS FOR ELECTRIC MOTORS PROTECTION Overview on the importance of electric motor protection. Every electric motor has operating limits. Overshooting these limits will eventually destroy it and the systems it drives, the immediate effect being operating shutdown and losses. This type of receiver, which transforms electrical energy into mechanical energy, can be the seat of electrical or mechanical incidents. Electrical a. Power surges, voltage drops, unbalance and phase losses causing variations in the absorbed current. b. Short circuits where the current can reach levels that can destroy the receiver. Mechanical a. Rotor stalling, momentary or prolonged overloads increasing the current absorbed by the motor and dangerously heating its windings. The cost of these incidents can be high. a. It includes production loss b. Loss of raw materials, c. Repair of the production equipment, d. Non-quality production and delivery delays. The economic necessity for businesses to be m

ELECTRIC INDUCTION MOTOR DESIGN: IEC MOTOR DESIGN LETTER GUIDE What are the motor design types that are provided by IEC? Motors covered by this IEC standard are classified by the following designs: Design N Normal torque three-phase cage induction motors intended for direct-online starting, having 2, 4, 6, or 8 poles and rated from 0.4 kW to 630 kW at frequencies of 50 Hz or 60 Hz. Design NY Motors similar to design N, but intended for star-delta starting. For these motors in star-connection, minimum values for Tl and TU of 25% of the values of design N may be expected. Design H High torque three-phase cage induction motors with 4, 6 or 8 poles, intended for Direct-online starting, and rated from 0.4 kW to 160 kW at a frequency of 60 Hz. Torques of IEC Design H are nearly identical to NEMA Design C. Design HY Motors similar to design H but intended for star-delta starting. For these motors in star-connection, minimum values for T1 and TU of 25% of the values of Design H  ma

ELECTRIC INDUCTION MOTOR DESIGN: NEMA MOTOR DESIGN LETTER GUIDE What are the motor design types that are provided by NEMA? NEMA Design Letter Changes in motor windings and rotor design will alter the performance characteristics of induction motors. Motors are designed with certain speed torque characteristics to match the speed torque requirements of the various loads. To obtain some uniformity in application, NEMA has designated specific designs of general purpose motors having specified locked rotor torque, breakdown torque, slip, starting current, or other values. The following graph shows the relationship between speed and torque that the motor produces from the moment of start until the motor reaches full load torque at rated speed. NEMA has established four different designs - A, B, C and D - for electrical induction motors. Different motors of the same nominal horsepower can have varying starting current, torque curves, speeds, and other variables. Selection of a particular

ELECTRIC MOTOR MOUNTING USING NEMA DIMENSIONS TUTORIAL GUIDE What are the guidelines in mounting electric motors using NEMA? NEMA has standardized motor dimensions for a range of frame sizes. Standardized dimensions include bolt-hole size, mounting base dimensions, shaft height, shaft diameter, and shaft length. Use of standardized dimensions allows existing motors to be replaced without reworking the mounting arrangement. In addition, new installations are easier to design because the dimensions are known. NEMA divides standard frame sizes into two categories, fractional horsepower and integral horsepower. The most common frame sizes for fractional horsepower motors are 42, 48, and 56. Integral horsepower motors are designated by frame sizes 143 and above. A T in the motor frame size designation for an integral horsepower motor indicates that the motor is built to current NEMA frame standards. Motors that have a U in their motor frame size designation are built to NEMA standards

MOTORS FOR POTENTIALLY EXPLOSIVE ATMOSPHERE DESIGN SPECIFICATION GUIDE What are the principles for designing explosion-safe electric motors? There are two main principles for explosion protection for electric motors. One is to design the motor so that no dangerous heat or spark occurs. This includes the increased safety version, EEx e. The other method is based on isolating any dangerous heat or spark inside the motor so as to prevent the ignition of any explosive mixture of gases outside the motor. This includes the version with flameproof enclosure, EEx d, and the version with pressurized enclosure, EEx p. These are the three internationally standardized versions that are suitable for motors to be installed in Zone 1. The "non-sparking" version, Exn, according to IEC 79-15 (1987) is intended for use in Zone 2. IEC 79-15 has not yet been transferred to a national standard, but this is expected to happen after it has been converted into a European standard in CENELEC. Br

ELECTRIC MOTOR SPECIFICATIONS ON TEMPERATURE CLASS AND OTHER TEMPERATURE RELATED CONSIDERATIONS GUIDE How to specify electric motors using temperature class as basis? Combustible gas or vapor and explosion-protected electrical equipment is divided into temperature classes T1 to T6 with regard to the ignition temperature of the gas or vapor and the maximum surface temperature of the equipment. Refer to Table1.4A - Temperature Class. Ignition temperature, thermal flashpoint, is the lowest temperature of a surface at which a substance ignites on contact with the surface. Hazardous area and zones Hazardous areas are rooms, spaces or areas in which an explosive gas mixture may occur under conditions such that electrical equipment, among other things, may have to meet certain requirements. Hazardous areas are categorized as zones as follows: Zone 0 - An area in which an explosive gas atmosphere is present continuously or is present for long periods. Zone 1 - An area in which an

CONVERT NEMA TO IEC ELECTRIC MOTOR ENCLOSURE CLASSIFICATION TUTORIALS How to convert NEMA to IEC  motor enclosure classification? NEMA enclosure classifications are developed by NEMA and used in the U.S./American market. Ingress Protection - IP - ratings are developed by the European Committee for Electro Technical Standardization (CENELEC) (described IEC/EN 60529), and specifies the environmental protection and enclosure provided. The table below can be used to convert from NEMA Enclosure Types to IEC Enclosure Types: source: 2010 IIEE Technical Manuals

EXPLOSIONPROOF MOTOR ENCLOSURE FORMAT DEFINITION How to group explosionproof motor according to its format? The explosionproof motor is a totally enclosed machine and is designed to withstand an explosion of specified gas or vapor inside the motor casing and prevent the ignition outside the motor by sparks, flashing or explosion. These motors are designed for specific hazardous purposes, such as atmospheres containing gases or hazardous dusts. For safe operation, the maximum motor operating temperature must be below the ignition temperature of surrounding gases or vapors. Explosionproof motors are designed, manufactured and tested under the rigid requirements of the Underwriters Laboratories. Hazardous location motor applications are classified by the type of hazardous environment present, the characteristics of the specific material creating the hazard, the probability of exposure to the environment, and the maximum temperature level that is considered safe for the substance crea

ENCLOSURE TYPE FOR ELECTRIC MOTOR SPECIFICATIONS How do they specify the enclosure of an Electric Motor? The enclosure of the motor must protect the windings, bearings, and other mechanical parts from moisture, chemicals, mechanical damage and abrasion from grit. NEMA standards MG1-1.25 through 1.27 define more than 20 types of enclosures under the categories of open machines, totally enclosed machines, and machines with encapsulated or sealed windings. The most commonly used motor enclosures are open dripproof, totally enclosed fan cooled and explosionproof. The Standards for IP Codes apply to the classification of degrees of protection provided by enclosure for all rotating machines. The designation used for the degree of protection consists of the letter IP (International Protection) followed by two characteristic numerals. When the degree of protection is specified by only one numeral, the omitted numeral is replaced by the letter X. For example, IPX5 or IP2X. The first Ch

ELECTRIC MOTOR FRAME SIZE STANDARD SPECIFICATIONS How is electric motor frame size being specified? Motor frame dimensions have been standardized with a uniform frame size numbering system. This system was developed by NEMA and specific frame sizes have been assigned to standard motor ratings based on enclosure, horsepower and speed. The current standardized frames for integral horsepower induction motors ranges from 143T to 445T. These standards cover most motors in the range of one through two hundred horsepower. Typical example of where you can locate the frame is shown in Fig 1.2.D – Frame No. The numbers used to designate frame sizes have specific meanings based on the physical size of the motor. Some digits are related to the motor shaft height and the remaining digit or digits relate to the length of the motor. The rerate, or frame size reduction programs were brought about by advancements in motor technology relating mainly to higher temperature ratings of insulating mate

INSULATION CLASS OF ELECTRIC MOTORS DISCUSSION How does electric motors being describe according to its insulation class? NEMA NEMA defines motor insulation classes to describe the ability of motor insulation to handle heat. The four insulation classes are A, B, F, and H. All four classes identify the allowable temperature rise from an ambient temperature of 40° C (104° F). Classes B and F are the most commonly used. Ambient temperature is the temperature of the surrounding air. This is also the temperature of the motor windings before starting the motor, assuming the motor has been stopped long enough. Temperature rises in the motor windings as soon as the motor is started. The combination of ambient temperature and allowed temperature rise equals the maximum rated winding temperature. If the motor is operated at a higher winding temperature, service life will be reduced. A 10° C increase in the operating temperature above the allowed maximum can cut the motor’s insulation

How do we interpret an electric motor nameplate? Motor standards are established on a country by country basis.Fortunately though, the standards can be grouped into two major categories: NEMA and IEC (and its derivatives). In North America, the National Electric Manufacturers Association (NEMA) sets motor standards, including what should go on the nameplate (NEMA Standard MG 1-10.40 "Nameplate Marking for Medium Single-Phase and Polyphase Induction Motors").