Standard motor

For produetion eontrol of small diameter nozzle welds a magnetic wheel scarmer has been build (Figure 4). One standard motor module drives the magnetic wheel and one standard motor module drives the Y-module slide. The two motors are connected to the Master Module. The scanner is controlled from a FORCE Institute PSP-3 ultrasonic acquisition unit with build-in scarmer controller. 

The Advanced Inspection Robot - AIR-1 is a portable (weight approx. 25 kg.) 6-axis articulated elbow type robot manipulator with 6 degrees of freedom. It is build from standard motor and control module components from FORCE Institutes Modular Scanner System and is controlled from within the UltraSlM/UlScan graphical generic robot control application. 

The electric motors are often the noisiest component of the centrifuge assembly. Most standard motors in the 75—250 kW range develop noise levels of 85 dbA (weighted sound pressure level using filter A, per the ANSI standard). A quiet motor can reduce this level by 5 dbA and should be used whenever noise is of concern. 

Induction generator This is a standard squirrel cage motor with additional treatment to weather the site conditions. The normal specifications are generally the same as for a standard motor. The permissible voltage and frequency variations are, however, wider as noted below ... 

For all the applications discussed above, which may require special starting and/or pull-out torques or speed variations, the use of static drives is more appropriate today. With the use of this technology, a standard motor can be made to perform any required duty, except the constructional features and the applicable deratings as discussed in Chapter 1. See also Example 7.1. 

Tbe use of special motors was more relevant until the 1980s. when solid-state technology was still in its infancy and wa.s not so widely applied. With the advent of static drives, as discus.sed in Sections 6.2-6.4, the use of standard motors is gradually becoming more common for all these applications. The drive it.self can alter the supply parameters to the required level to make a standard motor operate and perform within desired parameters, besides conserving energy. The purpose of describing a few of these applications is only to indicate their non-standard features, where a standard motor with normal controls may not be able to perform the required duties. 

The maintenance of such motors at site is easy, since the stator can be wound with readymade PVC insulated winding coils, and does not need a varnish impregnation and subsequent baking etc., unlike a standard motor. It is thus easy to rewind them at site. 

The locked rotor thermal withstand time is much higher than for a standard motor. 

This is a location safer than Zone I with a likelihood of concentration of explosive gases, chemical vapour or volatile liquids during processing, storage or handling. This would become a fire hazard only under abnormal conditions, such as a leakage or a burst of joints or pipelines etc. Such a condition may exist only for a short period. A standard motor with additional features, as di.scussed below, may also be safe for such locations. A non-sparking type. Ex. n , or an increased safety motor, type Ex. e , may also be chosen for such locations. 

These values are restricted by 10°C, compared to the working temperature prescribed for standard motors, as in Table 9.1. 

These applications have considerably more stringent performance requirements than any other application. Circulating water pumps, boiler feed pumps, forced-draught (FD) and induced-draught (ID) fans, pulverizers (ball mills) and condensate pumps are components in a thermal power station that may require extra safety in a standard motor to make it able to fulfil these requirements and withstand abnormal service conditions and system disturbances. Abnormal operating conditions may be one or more of the following ... 

The allowable pulley loads for standard motors are given in Table 8.10. These are recommended by a few manufacturers for their motors, but they are generally true for other motors also. 

Table B.10 Allowable pulley loads for standard motors...

While making selection of even for a standard motor, it is generally not possible to exactly match the rating of the machine with the load. The motor may have some reserve capacity. 

New catalogs for large induction motors ai e based on standard motors with Class B insulation of 80°C rise by resistance, 1.0 service factor. Previously, they were 60°C rise by thermometer, 1.15 service factor. 

Today s standard motor enclosure for indoor applications is the open, drip-proof enclosure for induction and high-speed synchronous motors. For large motors, open, drip-proof construction is available up to about 20,000 hp and is used for squirrel-cage, synchronous, and wound-rotor motors. 

Today, almost all large motors are designed specifically for a particular application and for a specific driven machine. In sizing the motor for the load, the horsepower is usually selected so that additional overload capacity is not required. Therefore, customers should not be required to pay for capability they do not require. With the elimination of the service factor, standard motor base prices have been reduced 4—5% to reflect the savings. Users should specify standard horsepower ratings, without service factor for these reasons ... 

Figure 7-5. There is no standard speed-torque curve for accelerating compressors. Attempting to make a standard motor to meet all needs (heavy line) would impose unnecessary demands on motor design [7].

Permits the use of a standard or, at least, a more-standard motor... 

Most standard motors are manufactured using non-hygroscopic NEMA Class B insulation. For added protection in an offshore environment, open drip-proof or weather protected motors should be specified with a sealed insulation system. NEMA Class F insulation is also available in most motor sizes and is advisable to provide an improved service factor. 

In Figure 3-50, where the pump operates at 1760 rpm (a standard motor speed under load) and has maximum efficiency at 1480 GPM and 132 feet head, the type specific speed is... 

When the actual maximum gear box horsepower is known from the manufacturer, it should be used as long as it is equal to or greater than the 5% allowance noted above. The impeller/fluid horsepower allowable variation should still be 10% or greater. For example, if the calculated required motor drive (or turbine drive) hp = 23, (i.e., 19.55/0.85), the next standard motor is 25 hp, so use this, never less than the 23 indicated above because 23 hp is non-standard, and no such motor hp exists. 

Read closest motor hp = 20. However, the 0.5 hp difference between the 19.5 and 20 may not be sufficient to handle die power loss in the gear box. Most industrial practice is to take the closest standard motor hp to the 22.9 hp determined above,. vhich is 25 hp. The gear box must have an output speed of 90 rpm and will use only the hp determined by the impeller shaft e en if the motor is larger, that is, 25 hp. It will only put out the net hp required, tliat is, the sum of impeller shaft and losses through the gear box. 

Figure 12-119C. AMCA standard motor positions for belt or chain drive centrifugal fans. Reprinted from AMCA Publication 99-86 Standards Handbook, 1986, Standard AMCA No. 99-2407-66, with written permission from Air Movement and Control Association International, Inc., 1986. All rights reserved.)...

Frame refers to standard motor housing frame as dimensioned by the NEMA (National Electrical Manufacturers Association) Code. 

Figure 14-2A. Alternating current (AC) induction motor cross-sectional view of 220/440V, 3-phase, 60-cycle, totally enclosed fan-cooled standard motor. (Used by permission Reliance Electric Co., Div. Rockwell Automation.)...

Do not mix special with standard motors on a single purchase order. If changes must be made later in specials, some delay can be avoided. 

NEMA Standards, Motors and Generators, ANSI/NEMA Standards Publication, No. MG 1-1978. 

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