900kW 10kV Wound-Rotor Slip Recovery Motor — Standby Unit Procurement Technical Specification

I. Project Background and Key Challenges

1. Current Site Equipment Status

• Original Motor: Slip recovery speed control three-phase asynchronous motor, Model YRK630-6, 900kW, 10kV, commissioned in 2015.

• Associated Fan: Howden axial flow fan, Model FAF-2350/1400-1.

• Years in Service: Both the motor and fan have been in continuous operation since 2015.

2. Procurement Objective

To procure one standby slip recovery speed control motor capable of directly replacing the existing motor when required, driving the existing Howden fan, and maintaining full compatibility with the existing slip recovery speed control system.

3. Risk of Accumulated Wear After Extended Operation

The existing fan has been in service for approximately eleven years. Bearing housings, coupling flanges, and the mounting foundation may have undergone cumulative deformation or micro-settlement that is not externally visible. Although the replacement motor will be manufactured strictly to the original engineering drawings, dimensional deviations introduced by long-term structural changes at the site could affect alignment quality and mechanical fit upon installation.

Therefore, the site survey must go well beyond a routine nameplate cross-check. It must constitute a systematic mechanical and electrical compatibility audit, with all findings formally documented and reviewed before manufacturing commences.

II. Site Survey and Interface Investigation Plan

Before the technical agreement is finalized, the Wolong motor supplier must deploy qualified engineers to carry out a comprehensive on-site survey of the existing motor installation and produce a full set of measured drawings and written records. The replacement motor's installation envelope must conform entirely to the existing foundation geometry to allow true drop-in substitution. Electrical termination locations, conduit entry directions, and auxiliary wiring configurations must replicate those of the current motor as closely as possible, so that the changeover can be completed without modifying existing power cables or control wiring runs.

2.1 Foundation and Motor Installation Dimensional Survey

The following items must be physically measured and recorded on-site:

• Overall foundation plan dimensions, including all boundary edges, hold-down bolt hole positions, bolt circle diameters, and the axial distance from the motor mounting face to the fan coupling centerline.

• Existing motor frame dimensions, including shaft centerline height, foot pad spacing, and axial shaft extension length.

• Clearance envelope around the installed motor, noting any adjacent structures, pipework, or cable trays that constrain the installation space.

The purpose is to guarantee that the new Wolong motor seats fully and evenly on the existing foundation without any unsupported areas or interference with surrounding structures after installation.

Note: The existing motor employs a wound-rotor construction with an IC616 forced ventilation cooling arrangement. The drive-end shaft extension incorporates a custom-length "E" dimension to accommodate the existing fluid coupling, and the available installation envelope on the non-drive end is particularly restricted due to adjacent ductwork. On-site measurements must be performed with calibrated instruments to the highest achievable accuracy, as any dimensional discrepancy will directly affect manufacturing tolerances and on-site installation quality.

2.2 Electrical Interface and Control System In-Depth Investigation

Main and Rotor Terminal Box Position Survey

The motor is equipped with separate terminal boxes for stator, rotor, and auxiliary circuits. For each terminal box, the following must be recorded:

• Three-dimensional spatial position relative to the motor frame (longitudinal, lateral, and height)

• Cable entry direction and conduit knockout sizes

• Internal terminal block configuration, terminal stud diameters, and available cable bend radius inside the box

This information is critical to confirming that all existing cable runs can be reconnected to the new motor without re-routing or extending conductors.

Rotor Circuit Interface Verification

As a wound-rotor machine, the rotor slip rings and brush gear arrangement must be surveyed in detail:

• Slip ring diameter, width, and surface finish specification

• Brush gear mounting bracket dimensions and brush pressure setting

• Rotor circuit cable termination method and connection point locations on the existing speed control cabinet

Any deviation in slip ring geometry between the existing and replacement motor could render the existing brush gear incompatible, necessitating costly modifications to the speed control system.

Auxiliary Equipment Interface Verification

The following auxiliary devices must be individually checked for model number, electrical rating, connection method, and physical mounting arrangement to confirm full compatibility with the existing monitoring and protection system:

• Stator and bearing temperature sensors (PT100 RTDs) — quantity, insertion depth, and terminal wiring

• Anti-condensation heaters — voltage rating, wattage, and thermostat interface

• Vibration sensors — mounting thread size, sensor type (velocity or acceleration), and signal cable connector type

• Bearing temperature detectors — location (drive end / non-drive end), sensor type, and wiring polarity

All interface specifications must be formally confirmed in writing between the site team and the motor supplier prior to issuing the manufacturing order, so that the replacement motor is delivered fully compatible with the existing auxiliary systems without any field modification.

III. Key Technical Requirements for the Replacement Motor

3.1 Electrical and Performance Parameters

3.2 Mechanical Interface Requirements

• Frame size, shaft centerline height, foot bolt pattern, and shaft extension dimensions must identically match the existing motor or be confirmed compatible with the existing foundation and coupling before manufacturing is approved.

• Shaft extension diameter, length, keyway dimensions, and surface finish must be verified against the existing coupling bore to confirm direct fit without machining.

• The motor mass and center of gravity must be assessed against the existing foundation load capacity before installation.

3.3 Rotor Circuit Compatibility

• Rotor open-circuit voltage, rotor rated current, and slip ring dimensions must be fully compatible with the existing brush gear and speed control cabinet.

• The rotor winding connection configuration (star or delta) must match the existing system exactly.

• Supplier must provide rotor circuit test data at the factory acceptance test stage for cross-verification against the original motor records.

IV. Factory Acceptance Test Requirements

Prior to shipment, the replacement motor must undergo the following factory acceptance tests, with the site owner's representative invited to witness:

• No-load and reduced-voltage running test

• Stator and rotor winding resistance measurement

• Insulation resistance and high-voltage withstand test

• Temperature rise test at rated load

• Vibration and noise measurement

• Slip ring surface runout and brush contact pressure verification

• Auxiliary device function check (heaters, PT100s, vibration sensors)

All test results must be documented in a formal factory test report and submitted to the purchaser for review and approval before the motor is released for shipment.

V. Installation and Commissioning Considerations

5.1 Pre-Installation Checks

• Verify that the foundation hold-down bolts and grout pads are in sound condition before the new motor is positioned. Any degraded grout or corroded anchor bolts must be remediated before installation proceeds.

• Inspect the existing coupling for wear, cracks, or dimensional change before reuse. If any anomaly is detected, the coupling must be replaced rather than reused with the new motor.

5.2 Shaft Alignment

• Shaft alignment must be performed using a laser alignment system, not dial gauges alone, given the criticality of the application and the extended service history of the driven equipment.

• Final alignment readings must be recorded and retained as part of the installation documentation package.

• Alignment must be re-checked after the motor has reached thermal equilibrium during initial commissioning runs, and corrected if necessary.

5.3 Rotor Circuit Reconnection

• Rotor circuit cables must be reconnected to the slip rings and speed control cabinet strictly in accordance with the original wiring diagram.

• Brush seating must be verified and brush pressure adjusted to the specified value before energization.

• A full functional test of the speed control system must be completed before the unit is returned to service.

VI. Applicable Standards

VII. Summary

This procurement specification covers the supply of one standby wound-rotor slip recovery speed control motor as a direct replacement for the existing unit driving the Howden axial flow fan. Given the extended service life of the existing installation, the site survey phase is treated as a critical risk mitigation activity rather than a formality, with particular attention given to foundation settlement, coupling wear, rotor circuit interface compatibility, and auxiliary device integration. Strict adherence to the survey, manufacturing verification, factory acceptance testing, and installation alignment requirements set out in this specification will ensure that the standby motor can be installed and commissioned reliably with minimum downtime when called upon.