Attachment_C_-_Specifications,_Inverter_Duty_Motors_2024.doc

Bid No. 6293

Specifications

IFB 6293A

Specifications

Specifications for Inverter Duty Motors (Variable Frequency Drive)

1. General All workmanship and materials shall conform to the latest NEMA and EASA standards.

The vendor shall have a working quality assurance program in place and shall provide a copy of the quality manual for review if requested.

The vendor shall provide the supervision, labor, engineering, materials, test equipment, tools and facilities required to inspect and repair the equipment described in this specification.

2. Reconditioning

a. Upon receipt, the vendor shall verify nameplate data and look for certification for VFD duty. When the original design is intended for VFD, continue with the winding recondition process. Report to the City when motor will require new windings.

b. Upon receipt, low voltage stator winding insulation resistance shall be measured with a 500 volt Megohm-meter; medium voltage stators (2400 - 4160 volts) shall be measured with a 1000 volt Megohm meter.

c. If practical, motor to be test run at rated voltage and frequency and any abnormalities documented.

d. Motor shall be completely dismantled, stator surge tested, and all parts cleaned. Windings shall be cleaned with a mild detergent, thoroughly rinsed to remove the detergent, and baked to dry.

e. After drying, winding insulation resistance shall be tested again with a megohm meter of the proper voltage. Minimum insulation resistance is one megohm, plus one megohm per 1000 volts of rating or part thereof, (i.e.:460 volt rating: one megohm + one megohm = 2 megohms; 4160 volt rating: one megohm + 5 megohms = 6 megohms). Windings shall be surged tested. Windings shall be revarnished and cured.

f. Rotors

(1) Rotors shall be inspected for evidence of damaged, cracked or open circuited bars or end rings. If there is evidence of faults, rotor shall be "Growler" tested. Any faults shall be reported to the City.

(2) Rotors shall be steam cleaned and suitably washed and dried.

(3) Rotors shall be mounted in a lathe between centers and all critical surfaces shall be dial indicated for runouts. Shaft, bearing, seal, journal and coupling surfaces shall be micrometer measured.

(4) Bearing housings and seal surfaces shall be micrometer measured. All measurements and test results shall be recorded and retained in a permanent record.

g. Journals, Seals and Housings

(1) Bearing shaft and housing fits shall be to Anti-Friction Bearing Manufacturer's Standards. Seals and seal surfaces shall be to manufacturer's standards.

(2) Restoration of journal, housing and seal surfaces shall be accomplished by metallizing and machining or by boring and bushing. Restoration of shaft coupling or pulley fits shall be accomplished by welding and machining. Knurling or Loc-Tite is unacceptable.

h. Balancing

(1) All 3600 RPM rotors and all rotors on which any repairs are made shall be dynamically balanced. Balancing shall be made in accordance with American Petroleum Institute standards (i.e: rotor weight x 4 - by RPM, assuming a rotor weight of 2000 pounds with a rotational speed of 3600 RPM, ounce inches of residual unbalance = 2000 x 4 - 3600 = 2.2).

i. Bearings

(1) Anti-Friction Bearings

(a) Verify bearing insulation and measure insulation resistance to ground. Minimum resistance should be One Megohm or larger at 40º C.

(b) Shall be replaced with high quality, regreasable bearings unless other specified. Oil lubricated bearings shall have the test lubricant drained, and tags shall be attached to the bearing housing and motor leads stating: "OIL BEARINGS BEFORE OPERATING".

(c) Bearings shall be hand-packed with grease specified by the City.

(d) All motors which do not have grease fittings shall have "Zerk" fittings installed. An extension shall be installed, if necessary, to allow for re-lubricating while the motor is running.

(e) Bearings shall be heated on a temperature-controlled induction heater for installation.

(2) Sleeve (Babbitted) Bearings

(a) Bearing bores and journal diameters shall be micrometer measured.

(b) Bearings shall be inspected for evidence of loose or cracked babbitt or worn thrust faces.

(c) Bearing-to-journal, clearance shall be 0.002 inch, plus 0.001 inch per inch of diameter (i.e.: 4 - inch journal bearing shall have 0.002 + 0.004 =0.006 inch).

(d) If necessary, bearings shall be re-babbitted with ASTM Grade 2 babbitt material.

3. Rewinding

a. All insulation materials shall be Class 155 (F) or higher.

b. Stripping

(1) Windings shall be removed by either using "Vapor-Phase" solvent system or temperature-controlled burn-out oven with over temperature suppression. Burn-out temperature not to exceed 750 F.

(2) Windings shall be removed in such a fashion as not to damage or distort the core iron. Upon removal of the old windings and insulation, the core must be thoroughly cleaned and inspected for burrs, etc.

c. Core Testing, Repair and Preparation

(1) The core shall be tested for core losses in "watts/pound" and for permeability. It must also be overexcited and checked for hot spots. These test results shall be documented.

(2) Any hot spots should be corrected by separating the short circuited laminations. If this is unsuccessful, the core shall be re-stacked or replaced. City shall be notified in the event that re-stacking or core replacement is necessary.

(3) After the core is repaired and an acceptable test is obtained, stator and core shall be prime painted.

d. Winding

(1) Random Wound Stators

(a) Slot liners and phase separators shall be Nomex-Mylar-Nomex or Dacron- Mylar-Dacron.

(b) Magnet wire shall be Quantum Shield ( Phelps Dodge) insulated. Verify for extra room insulation requirements.

(c) Coils shall be machine wound, with all wires individually tensioned to ensure uniformity and freedom from" Crossovers". Proper form shapes shall be used to give adequate end room clearance.

(d) All connections, jumpers and leads shall be taped and laced down in a neat, secure manner with adequate clearance to bearing brackets and air deflectors.

(e) All connections shall be silver brazing.

(f) Leads on TEFC motors shall be "Potted" where they pass through the stator frame.

(g) After winding and prior to varnish treatment, windings shall be surge-comparison tested. Windings shall be preheated prior to varnish treatment to eliminate "crazing". Windings shall be immersed (dipped) in Class 155 (F) or better, Thermosetting varnished and baked to cure.

(2) Form Wound Stators

(a) Coils shall be properly dimensioned and shaped (spread) to ensure proper fit and preclude pressure points. Coils shall be insulated to slot size. Use of slot liners to fill slots are unacceptable.

(b) Insulating system shall be comprised of copper wire strand insulated with DDG over a class H Poly-Amida-Imida Enamel, non-treated Mica Composite VPI-type tape, with an outer armor of Woven Fiberglass tape.

(c) Slot portion of coils shall be insulated with a minimum of three half- lapped layers of Mica tape for 2400 volts, and a minimum of four half-lapped for 4160 volts.

(d) Slot fillers and coil blocking shall be comprised of an absorbent material, such as Glass Fiber material.

(e) Connectors shall be made in “U” configuration and silver brazing. Connections shall be taped with a minimum of four layers of Mica tape, followed by one layer of Fiberglass tape.

(f) Leads shall be fine-stranded with tinned conductors.

(g) Lugs shall be installed with a compression tool and die of proper size.

(h) Completely-wound stator shall be Vacuum Pressure Impregnated in solventless Polyester resin, using suitable preheat, vacuum, and pressure to ensure a completely void-free insulating system. It will then be baked to cure. After curing, windings shall be over-coated with Class F or better Epoxy varnish.

(i) Windings shall be surge tested at twice rated voltage + 1000 volts.

e. Wound Rotors

(1) Reconditioning

(a) Windings shall be cleaned, tested and treated as per Section 2. “Reconditioning”.

(2) Stripping

(a) Windings shall be removed in accordance with Section 3. B. “Stripping”.

(3) Winding

(a) Form and Random Winding shall be conducted in accordance with Section 3. “Winding” except that DMD or NMN slot liners are permissible. All new copper shall be used.

(b) NOTE: Form Wound rotors shall not be converted to Random. Wound rotors shall not be constructions.

4. Re-assembly and Test

a. All excess varnish shall be removed from the core I.D. prior to assembly.

b. Interiors of motor frames and parts shall be painted with red insulating paint. This includes rotors, bearing, brackets, frame interiors and air deflectors. Windings shall not be painted.

c. After assembly, motor shall be secured to a precision leveled and isolated bed plate and test run at rated voltage and frequency. No load voltage and phase currents shall be recorded. Vibration mils displacement shall be measured and recorded in the horizontal, vertical and axial planes on both ends of the motor (or top and bottom of vertical motors). Vibration levels shall be in accordance with NEMA Standards relative to RPM.

d. Exterior of the motor shall be properly cleaned of rust and foreign material, primed painted and finish painted with a good grade of machinery enamel. Shaft extension shall be coated with a suitable solvent removable rust preventive material. Motor mounting feet or base shall be sanded and cleaned of all foreign matter. Nameplates shall be reconditioned or replaced with stainless steel, as necessary.

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