A. Scope
1.0 This specification provides guidelines for design and manufacture of low and medium voltage vertical squirrel cage induction motors on larger than NEMA-size frames.
2.0 Work governed by these specifications includes manufacture, testing and delivery of equipment constructed in accordance with the requirements presented herein.
3.0 Items not addressed by these specifications include, but are not limited to:
3.1 Unloading and installation.
3.2 All external connections.
B. Codes and Standards
1.0 All equipment shall be fabricated, assembled and tested in accordance with the most current applicable standards as defined by the following institutions:
1.1 American National Standards Institute (ANSI).
1.2 Institute of Electrical and Electronic Engineers (IEEE).
1.3 National Electrical Manufacturers’ Association (NEMA).
1.4 Anti-Friction Bearing Manufacturers’ Association (AFBMA).
2.0 All materials and equipment shall be labeled or listed as being approved by the Underwriters Laboratories (U.L.) whenever applicable.
2.1 Equipment offered as meeting the intent of the U.L. requirements may be acceptable subject to the approval of the Purchaser.
C. Conditions of Service
1.0 Motors shall be suitable for continuous operation on a three-phase, sixty hertz system rated _________volts.
2.0 Motors shall be designed to operate at rated load in a maximum ambient temperature of 40°C at a maximum altitude of 1,000 meters.
3.0 The location of installation will be either indoors or outdoors as dictated by the specific provisions for each motor.
D. Design Requirements
1.0 General
1.1 Motors shall be capable of withstanding all normal forces which may be imposed upon them during the course of normal operation, including starting and normal stops.
1.2 Motors shall be suitable for across-the-line starting and shall be able to start and accelerate the connected load to full load speed with 90% of rated voltage at the motor terminals.
1.3 Motors shall be capable of continuous operation at full load and rated frequency with a voltage variation of +10%.
1.4 Motors shall be capable of continuous operation at full load and rated voltage with a frequency variation of +5%.
1.5 Motor starting current shall not exceed a value equal to 650% of the motor full load current.
1.6 Motor installation in hostile environments subject to dust, moisture and/or corrosive atmospheric conditions shall have all parts given protective treatment such as U.S. MOTORS "CORRO-DUTY®" or equal.
2.0 Enclosure
2.1 Motors shall be furnished with one of the following enclosure types based on the location of installation and the specific requirements for each motor.
2.1.1 Weather Protected, Type I (WP-I)
2.1.2 Weather Protected, Type II (WP-II)
2.1.3 Totally Enclosed, Fan Cooled (TEFC)
2.1.4 Totally Enclosed, Class I, Group D, Division 1 Explosion-proof (XP)
2.2 Openings on all Weather Protected designs shall be covered with metal guard screens having a mesh size no larger than ½ inch square.
2.2.1 Weather Protected Type I motors shall be designed to protect internal components from falling water and debris at angles up to 100 degrees from vertical.
2.2.2 When specified, Weather Protected Type II designs shall be furnished with removable, cleanable and reusable air filters over intake air openings.
2.3 Enclosures shall be of fabricated steel or cast iron construction in accordance with the manufacturer’s standard design. Canopy caps shall be of aluminum, cast iron or sheet metal and shall be easily removable for maintenance purposes.
2.4 Motors to be installed in locations where moisture may collect shall be furnished with drain openings and plugs. In the case of Explosion-proof motors, drains and breathers shall be furnished and shall be of the type approved by U.L.
3.0 Stator Construction
3.1 Stator laminations shall be of fully processed steel. Each lamination surface shall be given the necessary treatment so as to have core plate type C-5 insulation.
3.2 Stator windings for system voltages above 600 volts shall be form wound of rectangular copper magnet wire. Aluminum magnet wire is not acceptable. Individual coils shall be insulated with mica bearing tape prior to insertion. Coil extensions shall be blocked and braced sufficiently to minimize movement during normal starting and running conditions at full rated voltage.
3.3 Insulation
3.3.1 Insulation system shall be Class B or better.
3.3.2 Insulation systems shall receive a minimum of two vacuum pressure impregnation treatments using a 100% solids epoxy resin.
3.3.3 When specified, a completely sealed insulation system shall be supplied. This system shall be capable of passing the NEMA MG1-20.48 water immersion test and shall be U.S. MOTORS "EVERSEAL", or equivalent system.
3.3.4 When specified, motors to be rated for variable frequency drive applications shall meet NEMA MG-1 Part 31 dated 1993 and shall be U.S. MOTORS Inverter Grade® insulation system or equal. The insulation system shall be warranted for a minimum of 3 years operation on VFD power which shall not be limited by maximum cable length restrictions.
3.4 Temperature rise shall not exceed the limits defined by NEMA for Class B insulation systems while operating at nameplate horsepower, frequency and voltage.
3.4.1 In the case of a particular rating where a Class F temperature rise is required, motors shall be furnished with Class F or better insulation.
4.0 Rotor Construction
4.1 Rotors shall be of cast or fabricated aluminum in accordance with manufacturer’s standard design.
5.0 Bearings
5.1 Bearings supplied shall be of type and size sufficient to satisfy thrust loading requirements for each motor in accordance with manufacturer’s standard design. Bearings shall be rated for an in-service B-10 life of 8,800 hours.
5.2 Thrust Bearings
5.2.1 Motors shall be designed and constructed with thrust bearings on top to allow inspection and/or replacement without requiring complete disassembly of motor.
5.2.2 Thrust bearings shall be deep-groove ball, angular contact ball or spherical roller type. Bearings mounted back-to-back or in tandem are acceptable and may be furnished when required according to manufacturer’s standard design.
5.2.2.1 Deep-groove ball bearings shall be used only on normal thrust design motors and shall be capable of handling thrust loads in either direction.
5.2.2.2 High thrust design motors shall be supplied with angular contact ball bearings whenever possible and in accordance with manufacturer’s standard design.
5.2.2.3 Where thrust requirements restrict the use of angular contact bearings, spherical roller bearings shall be furnished.
- When required, motors furnished with spherical roller bearings shall also be provided with a system of coils in the oil reservoir for the circulation of cooling water.
- Spherical roller bearings shall be spring loaded to keep the lower bearing race in contact and prevent bearing damage during starting and momentary upthrust conditions.
5.3 Guide Bearings
5.3.1 Guide bearings shall be deep-groove ball type and shall be located at the bottom of the motor.
5.3.2 Guide bearings may be stacked when necessary according to manufacturer’s standard design to accommodate specified upthrust conditions.
5.3.3 Guide bearings or bearing assemblies shall be provided with sufficient means for preventing the leakage of lubricant or entrance of foreign matter along the shaft.
5.4 Lubrication
5.4.1 Thrust bearings shall be oil lubricated and contained in an oil reservoir with oil sight level gauge and oil fill and drain openings with plugs.
5.4.2 Deep-groove ball bearings furnished as thrust bearings for normal thrust motors shall be grease lubricated. When furnished as guide bearings for high thrust units, they shall be oil lubricated.
5.4.2.1 Grease lubricated bearings shall be furnished with provisions for in-service positive lubrication. A drain shall be provided to guard against over lubrication.
6.0 Noise Level
6.1 Sound pressure levels shall be measured according to ANSI S 12.51, ANSI S 12.54 and ANSI S12.55 as referenced in NEMA MG1 Part 9 and shall not exceed 90 decibels as measured on the A-Weighted Scale at a distance of five (5) feet from any motor surface under no load, free field conditions.
7.0 Nameplates
7.1 Motor nameplates shall be of stainless steel and shall be securely fastened to the motor frame with pins of a like material.
7.2 The following information shall be contained on the motor nameplate as a minimum:
7.2.1 Rated Horsepower
7.2.2 Full Load Speed
7.2.3 Frequency
7.2.4 NEMA KVA Code and Design Letter (when applicable)
7.2.5 Rated Voltage
7.2.6 Manufacturer’s Serial Number
7.2.7 Service Factor
7.2.8 Insulation Class
7.2.9 Maximum Ambient
7.2.10 Full Load Current at Nameplate Voltage
7.2.11 Frame Size Designation
8.0 Terminal Boxes
8.1 Terminal boxes shall be of fabricated steel or cast iron construction to be compatible with the motor enclosure specified and when possible, shall be diagonally split and capable of rotation in 90° increments. Boxes not suitable for rotation must be capable of top entry.
8.2 The area in which the main terminal box is connected with the motor frame shall be fully gasketed in order to prevent entrance of foreign matter into the motor and to provide support for the stator leads where they pass through the motor frame.
8.3 A properly sized grounding terminal shall be mounted in the main terminal box when specified.
8.4 The main terminal box shall be sufficiently oversized to allow stress cone terminations of shielded power cables and to allow mounting of any surge capacitors, lightning arrestors or current transformers as may be specified.
9.0 Leads
9.1 Main motor leads shall have EPDM or equal type jackets and shall be permanently tagged for identification.
9.2 The relationship between lead markings and the direction of rotation shall be indicated on a separate motor nameplate.
E. Accessories
1.0 Space Heaters
1.1 When specified, motors shall be furnished with space heaters to provide sufficient wattage to maintain the internal temperature of the motor at a level approximately 10°C above the ambient temperature while the motor is not in operation.
1.2 Space heaters shall be of the silicone rubber strip type attached directly to the stator end turns. When specified, the leads shall be brought out to an auxiliary terminal box.
1.3 Space heaters shall be rated for operation on a single phase, 60 hertz, 120 volt system.
2.0 Protective Devices
2.1 When specified, stator winding protection shall consist of one or more of the following systems:
2.1.1 Six (6) 120 phm nickel resistance-type temperature detectors (RTD’s) embedded in the stator windings, two (2) per phase. Each detector shall have its leads wired to an auxiliary terminal box.
2.1.2 One (1) positive temperature coefficient (PTC) thermistor temperature sensor embedded in each phase of the stator winding and corresponding solid state electronic control. Thermistor system shall be U.S. MOTORS "THERMA-SENTRY", or equal.
2.1.3 Three (3) bi-metallic thermostats of the automatic reset type, with normally closed contacts, mounted one per phase. Each thermostat shall be furnished with leads suitable for connection to the control circuit.
2.2 When Specified, bearing protection shall consist of one of the following:
2.2.1 Two (2) 120 ohm nickel resistance-type temperature detectors (RTD’s), one (1) per bearing, mounted as closely as possible to the outer surface of each bearing. Each detector shall have its leads wired to a terminal block located in an auxiliary terminal box.
2.2.2 Two (2) bearing temperature relays one (1) per bearing, furnished with indicating scale.
2.2.3 Two (2) dial type thermometers, one (1) per bearing.
2.2.4 Two (2) iron or copper constantan thermo-couples, one (1) per bearing.
2.3 When specified, surge protection shall be provided in form of surge capacitors and lightning arrestors mounted, one (1) per phase in the main terminal box.
2.4 When specified, differential ground protection shall consist of three (3) window-type current transformers, mounted one (1) per phase in the main terminal box. Leads of each phase shall be passed through individual current transformers. Transformers shall be of a ratio specified by the Purchaser at time of order placement.
3.0 Metering
3.1 When specified for metering purposes, one (1) bar or window-type current transformer shall be furnished mounted in the main terminal box.
F. Testing
1.0 When specified, one (1) motor shall be given a complete initial test in accordance with IEEE 112 method B and shall include the following items:
1.1 Current Balance
1.2 High Potential Test
1.3 Vibration Test
1.4 Winding Resistance
1.5 Locked Rotor Current
1.6 No Load Running Current
1.7 Full Load Heat Run
1.8 Full Load Percent Slip
1.9 Efficiency at 100%, 75% and 50% Load
1.10 Power Factor at 100%, 75% and 50% Load
2.0 When specified, noise test shall be performed in accordance with IEEE standard 85 decibel.
3.0 When specified, water immersion test shall be performed in accordance with NEMA MG 1-20.48.
4.0 Five (5) copies of certified test reports shall be submitted to the purchaser upon completion of all required tests.
5.0 Purchaser reserves the right to witness any or all of the tests specified to be performed. Prices for this shall be included as a separate item in the seller’s quotation.
G. Submittal Data
1.0 Required with Proposal
1.1 Preliminary Dimension Print and Frame Size
1.2 Approximate Motor Weight
1.3 Complete Motor Nameplate Information
1.4 Motor Performance Data, including the following:
1.4.1 Guaranteed minimum efficiencies at 100%, 75% and 50% of full load.
1.4.2 Guaranteed minimum power factor at 100%, 75% and 50% of full load.
1.4.3 Locked Rotor Current
1.4.4 Full Load Current
1.4.5 Starting Torque
1.4.6 Full Load Torque
1.4.7 Breakdown Torque
1.5 Complete Description of Testing Facilities.
1.6 Job site Storage Requirements.
2.0 Required within six (6) weeks of Purchase Order Award
2.1 Certified Dimension Prints
2.2 Recommended Spare Parts List Priced
3.0 Required with motor upon shipment
3.1 Operation and Maintenance Manuals
3.2 Connection Diagrams
3.3 Test Reports as Specified
H. Acceptable Manufacturers
1.0 Motors shall be U.S. MOTORS "TITAN Line" or approved equal.