OR FATAL INJURY FROM ELECTRICAL SHOCK IS POSSIBLE.
Refer to Section 3.2.3 for grounding instruction details.
1.3 General Description
The motor is an alternating current squirrel cage induction motor of forced ventilated construction designed for use with Variable Frequency Drives only. The construction of this motor results in a totally enclosed, forced air-cooled machine (IP45) with IP54 minimum terminal boxes. *Please refer to the ATEX Certificate for proper air flow requirement of motor rating. The motor requires a minimum of 3400 SCFM to be provided to the inlet of the motor. The motor is provided with openings for duct connections for air inlet and exhaust. Ducting must remain in place for certification.
The stator and coil assembly is an integral part of the frame with the stator laminations welded directly to the frame structure. The motor frame is equipped with removable end frames which provide support for the bearings.
Principle Components
A 3-phase induction motor has two main parts: A stationary stator (1) and a revolving rotor (2). The rotor is separated from the stator by an air gap (5). The stator consists of a steel frame (3) that encloses and secures the laminated stator core (4). The stator core is made from thin laminations stacked to form a hollow cylinder. At the air gap, along the inner circumference of the laminations, the stator laminations have evenly spaced slots that contain the stator winding.
– Refer to Figure 3
The rotor is also made up of punched laminations carefully stacked to create openings (slots) along the air gap. Copper rotor bars (6) are inserted into the slots and connected (short circuited) at each end by copper end rings (7). Bars are swaged to the slot to avoid movement as a counter-measure against sparking and vibration. The rotor forms a cage and is referred to as “squirrel cage” rotor.
The entire rotor assembly, consisting of stacked laminations, bars, and end rings, is secured onto the shaft (8). The shaft rotates between bearings at each end (9) and (10).
1.4 Motor Construction 1.4.1 Stator Core
The motor stator core is constructed from thin electrical steel laminations and coated insulated to minimize hot spots and stack losses. The steel laminations are assembled under pressure to form the stator core. The stator core is welded to the frame structure.
Insulated stator coils constructed of copper magnet wire are inserted in the stator slots.
The stator coils and core slots are insulated with electrical insulating material. The stator assembly is vacuum and pressure impregnated with electrical grade varnish and baked to insure proper bonding qualities, to give high dielectric strength and maximum moisture resistance. Stator leads are routed to the appropriate location on the motor frame for terminal termination.
1.4.2 Stator Winding
The stator winding is a series of copper coils placed in the laminated stator slots core.
The winding is connected so that a 3-phase power source produces a rotating magnetic field. This magnetic field in turn induces a rotor field that interacts with the stator field to produce torque in the rotor.
The copper in the stator winding is insulated with materials suitable for operation at (Class H) temperature. The thickness and strength of the insulating material are suitable for the voltage stresses applied to the winding during the Variable Frequency Drive Operation.
1.4.3 Squirrel – Cage Rotor
The rotor is also made up of punched laminations carefully stacked to create openings (slots) along the air gap. Copper rotor bars are inserted into the slots and connected (short circuited) at each end by copper end rings. Bars are swaged into the rotor slot to avoid movement and as a counter-measure against sparking and vibration. The rotor forms a cage and is referred to as a “squirrel cage” rotor.
The entire rotor assembly consists of stacked laminations, bars and end rings. All components are secured onto the shaft. The shaft along with the rotor assembly rotates and is supported by bearings mounted at each end. The shaft has a tapered shaft extension for ease hub installation for coupling. For detailed information, see the Outline and Mounting drawing included in the Drawing and Data Package.
1.4.4 Bearings
The drive end of the rotating shaft assembly is supported by a fixed ball bearing or a cylindrical roller bearing - see motor outline for specific bearing application.
Bearing re-lubrication is required at 3,000 hour intervals or on a periodic basis to extend bearing life. Bearing replacement is recommended at 25,000 hours of operation. See
“Preventive Maintenance Schedule” for proper lubrication and factory installed lubricant specifications.
1.4.5 Frame
The frame is fabricated of steel members welded to plate end rings and press plates.
Steel foot plates are welded to the frame assembly to provide rigid support of the motor and maintain its alignment with the driven load. Lifting provisions are installed on the frame to facilitate lifting the complete motor with a conventional overhead hoist. A steel cover is welded to the frame structure to provide additional stiffness to the frame.
1.4.6 Accessories
National Oilwell Varco motors are available with accessories such as speed encoders and other components required for motor application. The motors require a forced-air ventilation system. Refer to the motor accessory description provided in the Drawing and Data Package of this manual for specific information regarding the accessories and configuration of the motor. (Motor Certification does not include accessories.)
If speed encoders are mounted on the NDE side of shaft, special precaution should be taken to avoid circulating currents using appropriate insulated
hardware for installation.
All accessories must have certification ratings matching or more severe to maintain motor certification.
1.4.7 Variable – Frequency Operation
This motor is to be operated with (powered by) a Variable Frequency Drive. This motor is designed to be operated with (powered by) a Variable Frequency Drive. The list of approved drives is listed in the current ATEX Certificate. If there is any concerns about any approved Variable Frequency Drive please contact the manufacture, National Oilwell Varco, Sugar Land, Texas.