8.5 Motor Nameplate Data, Insulation Classes & Megohmmeter Testing

8.5 Motor Nameplate Data, Insulation Classes & Megohmmeter Testing

Quick Answer: Motor nameplates per NEMA MG 1 and CSA C22.2 No. 100 provide critical engineering ratings: voltage, full-load amps (FLA), duty cycle, and Service Factor (SF, e.g. 1.15 allowing 15% continuous overload). NEMA Code Letters (A through V) quantify locked-rotor kVA/HP, used to calculate locked-rotor starting current: $\text{LRA} = \frac{\text{kVA/HP} \times \text{HP} \times 1000}{\sqrt{3} \times V_{\text{line}}}$. Motor insulation thermal classes include Class B ($130^\circ\text{C}$), Class F ($155^\circ\text{C}$), and Class H ($180^\circ\text{C}$); under the Arrhenius 10°C rule, every 10°C rise above rated limits cuts insulation life by 50%. Diagnostic testing mandates four-wire Kelvin bridge winding resistance balance (unbalance <2%) and high-voltage DC megohmmeter testing normalized to 40°C. Quality insulation exhibits a Polarization Index ($\text{PI} = \frac{R_{\text{10min}}}{R_{\text{1min}}}$) of 2.0 or greater and Dielectric Absorption Ratio ($\text{DAR} = \frac{R_{\text{60s}}}{R_{\text{30s}}}$) above 1.4, followed by strict capacitive discharge per CSA Z462.

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1. Decoding Industrial Motor Nameplates (NEMA MG 1 & CSA C22.2 No. 100)

Under Canadian Electrical Code (CEC Part I, Section 28) and provincial safety regulations, every motor installed in an industrial facility must carry a permanent, legible certification nameplate conforming to NEMA Standard MG 1 and CSA Standard C22.2 No. 100 (Motors and Generators).

+-----------------------------------------------------------------------------------------+
|                                INDUSTRIAL AC INDUCTION MOTOR                            |
|   MOD: 354T-X480                       HP: 75                  FRAME: 365T              |
|   VOLTS: 575                           PHASE: 3                HERTZ: 60                |
|   FLA: 72.0 A                          RPM: 1775               SERVICE FACTOR: 1.15     |
|   NEMA DESIGN: B                       CODE: G                 DUTY: CONT               |
|   INSUL CLASS: F                       AMB: 40 deg C           ENCL: TEFC               |
|   NEMA NOM EFF: 95.4%                  POWER FACTOR: 86.5%     BEARINGS: DE 6314 / ODE  |
+-----------------------------------------------------------------------------------------+

Mandatory Nameplate Parameters & Technical Interpretations

1. Rated Voltage & Frequency: The nominal line-to-line voltage (e.g., 208 V, 230/460 V, 575 V) and frequency (60 Hz in Canada) at which the motor is engineered to operate. Under NEMA MG 1, motors are rated to operate successfully with a voltage variation of $\pm 10%$ at rated frequency, though performance (torque and temperature rise) will vary.
2. Full-Load Amperes (FLA): The continuous current drawn by the motor at rated line voltage, rated frequency, and rated mechanical shaft horsepower output. This figure is used for sizing motor branch-circuit overload protection (overload heaters/electronic overload relays per CEC Rule 28-306).
3. Rated Horsepower (HP) & RPM: The mechanical output power available at the motor shaft (1 HP = 746 Watts) and the actual full-load rotational speed of the rotor ($N_r$) when delivering rated horsepower.
4. Duty Rating: Defines the thermal operating cycle:
   • Continuous (CONT): Motor can be operated indefinitely at rated load without exceeding its insulation thermal limits.
   • Intermittent (15, 30, or 60 min): Motor is rated only for short cyclical periods (e.g., crane hoists, valve actuators, roll-up doors) and requires cooling periods between operations.
5. Ambient Temperature Rating: The maximum temperature of the surrounding air in which the motor can operate at full load without overheating. Standard industrial rating is $40^\circ\text{C}$ ($104^\circ\text{F}$). If operated in higher ambient temperatures (e.g., a steel mill boiler room at $55^\circ\text{C}$), the motor must be derated in horsepower capacity.

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2. Service Factor, Duty Cycle & Dual-Voltage Lead Configurations

Motor Service Factor (SF)

The Service Factor (SF) is a multiplier indicating the continuous overload power that a motor can deliver without suffering immediate catastrophic insulation damage, provided it operates at rated voltage, frequency, and standard $40^\circ\text{C}$ ambient:

$$\text{Permissible Continuous Overload HP} = \text{Rated HP} \times \text{SF}$$

• Standard industrial motors typically have a Service Factor of 1.15, while specialty or explosion-proof motors often carry a Service Factor of 1.00.
• A 75 HP motor with an SF of 1.15 can continuously deliver $75 \times 1.15 = 86.25\text{ HP}$. Under this condition, continuous allowable current is $FLA \times SF = 72\text{ A} \times 1.15 = 82.8\text{ A}$.

Critical Engineering Trade-Off: Operating a motor within its service factor is intended for temporary peak production demands or unexpected process variations. It is not meant for routine continuous design sizing. Continuous operation at 1.15 SF increases internal winding temperature by $10^\circ\text{C}$ to $15^\circ\text{C}$, cuts insulation lifespan by approximately 50%, reduces motor operating efficiency, and lowers the operating power factor.

Dual-Voltage Motor Lead Configurations (9-Lead & 12-Lead)

Many three-phase motors are wound for dual-voltage operation (e.g., 230/460 V or 347/600 V) to allow inventory flexibility. A 9-lead dual-voltage motor contains three internal phase groups, each split into two equal winding halves:

   LOW VOLTAGE (PARALLEL-WYE: 230 V)           HIGH VOLTAGE (SERIES-WYE: 460 V)

        L1 ────┬─── T1                              L1 ─────── T1
               └─── T7                                         T4 ───┬─── T7 (Spliced)
        L2 ────┬─── T2                              L2 ─────── T2
               └─── T8                                         T5 ───┬─── T8 (Spliced)
        L3 ────┬─── T3                              L3 ─────── T3
               └─── T9                                         T6 ───┬─── T9 (Spliced)
        Tie Together: T4 + T5 + T6                  Tie Together: None (T4-T7, T5-T8, T6-T9)
        (Forms internal neutral)                    (Neutral is internally formed by coils)

• Low Voltage (Parallel-Wye): Line conductors connect to paired leads: $L1 \to T1+T7$, $L2 \to T2+T8$, $L3 \to T3+T9$. Leads $T4$, $T5$, and $T6$ are tied together to form a common internal neutral.
• High Voltage (Series-Wye): Line conductors connect to: $L1 \to T1$, $L2 \to T2$, $L3 \to T3$. Winding halves are connected in series by splicing $T4 \to T7$, $T5 \to T8$, and $T6 \to T9$. The neutral point is formed internally by the factory connection of the second coil set.

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3. NEMA Locked-Rotor Code Letters & Inrush Current Calculations

The NEMA Code Letter on a motor nameplate indicates the locked-rotor starting kVA per horsepower drawn by the motor at standstill ($s = 1.0$) when energized at rated voltage and frequency.

NEMA MG 1 Code Letter Table

Calculating Locked-Rotor Amperes (LRA)

Electricians and power engineers use the upper limit of the NEMA Code Letter to calculate maximum starting current for sizing short-circuit protective devices (fuses and circuit breakers per CEC Table 29) and verifying upstream transformer voltage drop:

$$\text{Total Starting kVA} = \text{kVA/HP} \times \text{HP}$$ $$\text{LRA} = \frac{\text{Total Starting kVA} \times 1000}{\sqrt{3} \times V_{\text{line}}}$$

Combined formula:

$$\text{LRA} = \frac{(\text{kVA/HP}) \times \text{HP} \times 1000}{\sqrt{3} \times V_{\text{line}}}$$

Step-by-Step Calculation Example

Scenario: Calculate the maximum locked-rotor starting current for a 75 HP, 575 V, 3-phase motor with NEMA Code Letter G.

1. Identify the upper limit for Code G from the table: $6.29\text{ kVA/HP}$.
2. Calculate total locked-rotor kVA: $$\text{Starting kVA} = 6.29 \times 75 = 471.75\text{ kVA}$$
3. Calculate locked-rotor line amperes: $$\text{LRA} = \frac{471.75 \times 1000}{1.732 \times 575} = \frac{471,750}{995.9} \approx 473.7\text{ A}$$

Compared to the full-load running current of 72 A, the locked-rotor starting current is $6.58 \times \text{FLA}$. Upstream protection must be coordinated to ride through this 474 A inrush for the duration of the acceleration period.

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4. Motor Insulation Classes, Thermal Life & Enclosure Designations

Thermal Insulation Classifications

The electrical insulation system separating copper windings from each other and from the grounded stator core is the most vulnerable component of an electric motor. NEMA and IEEE standards classify insulation systems by their maximum continuous operating temperature rating:

   Class A (105 deg C) ──> [ Obsolete / Vintage ]
   Class B (130 deg C) ──> [ 40 C Amb ] + [ 80 C Rise  ] + [ 10 C Hot Spot ]
   Class F (155 deg C) ──> [ 40 C Amb ] + [ 105 C Rise ] + [ 10 C Hot Spot ] <── Modern Industrial Standard
   Class H (180 deg C) ──> [ 40 C Amb ] + [ 125 C Rise ] + [ 15 C Hot Spot ] <── Severe Duty / High Ambient

• Class A ($105^\circ\text{C}$): Obsolete; found only in antique equipment utilizing organic cotton, silk, or paper soaked in varnish.
• Class B ($130^\circ\text{C}$): Historically standard for industrial motors; uses inorganic materials (mica, glass fiber) with synthetic resin binders.
• Class F ($155^\circ\text{C}$): The universal modern industrial standard. Built with high-temperature polyamide, epoxy resins, and glass cloth.
• Class H ($180^\circ\text{C}$): Used for extreme-duty, high-ambient, mining, and aerospace applications; incorporates silicone resins and advanced fluorocarbons.

The Arrhenius 10°C Rule of Thermal Degradation

Chemical degradation and oxidation of electrical insulation follow the Arrhenius reaction rate principle:

The 10°C Rule: For every $10^\circ\text{C}$ increase in continuous operating temperature above the rated thermal limit of the insulation system, the effective operational life of the insulation is halved (cut by 50%). Conversely, operating an insulation system $10^\circ\text{C}$ below its rated maximum doubles its expected lifespan.

Industrial Specification Practice: Many heavy industrial specifications mandate "Class F insulation with Class B temperature rise." This means the motor is manufactured with $155^\circ\text{C}$ materials but engineered to run at a lower $130^\circ\text{C}$ temperature rise under full load. This provides an enormous $25^\circ\text{C}$ thermal buffer, extending motor winding life by nearly a factor of four!

Industrial Motor Enclosure Designations

1. Open Drip-Proof (ODP): Internal fan draws ambient air directly across the bare windings. Louvers prevent liquid drops falling within $15^\circ$ of vertical from entering. Suitable only for clean, dry, climate-controlled indoor mechanical rooms.
2. Totally Enclosed Fan-Cooled (TEFC): The universal industrial standard. No free exchange of air between the inside and outside of the motor frame. An external shaft-mounted fan blows ambient air across external cooling fins on the cast-iron frame. Ideal for dirty, wet, dusty industrial environments (sawmills, chemical plants, mines).
3. Explosion-Proof (XP): Heavy cast-iron or cast-steel enclosure engineered per CEC Section 18 for hazardous locations (Class I, Division 1 / Zone 1). It is designed to contain an internal explosion of flammable gas or vapor without rupturing and without allowing sparks or hot flames to escape through machined flame paths into the surrounding atmosphere.

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5. Winding Resistance Balance Testing (Kelvin Bridge / DLRO)

The Necessity of Sub-Ohm Precision

Before commissioning a new motor or when troubleshooting thermal tripping, an electrician must verify that the resistance of all three stator phase windings is balanced. However, large three-phase industrial motors have winding resistances that are extremely small—often between $0.01\ \Omega$ and $1.0\ \Omega$.

A standard two-wire handheld digital multimeter (DMM) cannot measure sub-ohm resistances accurately. The resistance of the test leads ($0.1\ \Omega$ to $0.3\ \Omega$) and test probe contact resistance introduce measurement errors that can exceed 100% of the actual winding resistance.

   [ Constant Current Source ] ───────────────────────────────────────────┐
         │ (Current Lead C1)                             (Current Lead C2)│
         ▼                                                                ▼
   ( Terminal T1 ) ───[ Copper Winding Under Test: R_winding ]─── ( Terminal T2 )
         ▲                                                                ▲
         │ (Potential Lead P1)                         (Potential Lead P2)│
   [ High-Impedance Voltmeter ] ──────────────────────────────────────────┘

The Four-Wire Kelvin Bridge Principle (DLRO)

Electricians must use a Digital Low-Resistance Ohmmeter (DLRO) or four-wire Kelvin bridge:

• Two outer leads ($C1$ and $C2$) inject a regulated, constant DC test current (typically 1 A to 10 A) through the winding.
• Two inner leads ($P1$ and $P2$) measure the millivolt voltage drop directly across the winding terminals.
• Because the voltmeter has near-infinite internal impedance, virtually zero current flows through the potential leads, completely eliminating test lead resistance and contact resistance from the measurement.

Resistance Balance Acceptance Standard

Measure phase-to-phase resistance across all three terminal pairs ($T1-T2$, $T2-T3$, $T3-T1$). In a healthy three-phase motor, the maximum resistance unbalance between any two phases must not exceed 2% (or at most 3% in large older machines):

$$R_{\text{average}} = \frac{R_{12} + R_{23} + R_{31}}{3}$$ $$\text{Unbalance } \% = \frac{|R_{\text{phase}} - R_{\text{average}}|_{\text{max}}}{R_{\text{average}}} \times 100\%$$

An unbalance exceeding 2% indicates turn-to-turn short circuits, high-resistance internal crimp connections, loose terminal lugs, or cracked coil brazing, any of which will cause severe phase current unbalance, localized overheating, and imminent motor failure.

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6. Megohmmeter Insulation Resistance Testing & Temperature Correction (IEEE 43)

Objective & Test Voltage Selection

The Megohmmeter (Megger) applies a high DC test voltage between the motor winding conductors and the grounded motor frame to measure leakage current passing through the ground-wall insulation system.

In accordance with IEEE Standard 43-2013 (Recommended Practice for Testing Insulation Resistance of Electric Machinery), the test voltage must be selected based on the motor's rated line-to-line voltage:

Minimum Acceptable Insulation Resistance Values

• Classical Rule of Thumb: Minimum resistance must equal $1\text{ M}\Omega$ plus $1\text{ M}\Omega$ per kilovolt of operating voltage (e.g., for a 600 V motor: $1 + 0.6 = 1.6\text{ M}\Omega$).
• Modern IEEE Standard 43-2013 Thresholds:
  • $5\text{ M}\Omega$ minimum for older machines manufactured before 1970 or random-wound stator coils.
  • $100\text{ M}\Omega$ minimum for modern form-wound or random-wound machines utilizing epoxy-resin or synthetic insulation systems.

Temperature Correction to 40°C ($R_{40}$)

Insulation resistance varies exponentially with temperature: as insulation temperature rises, electrical resistance drops dramatically because thermal energy mobilizes charge carriers.

To compare insulation readings accurately over time or against standard benchmarks, all field megohmmeter readings must be normalized to a standard reference temperature of $40^\circ\text{C}$ using the IEEE 43 correction formula:

$$R_{40} = K_T \times R_T$$ $$K_T = (0.5)^{\frac{40 - T}{10}}$$

Where:

• $R_{40}$ = Corrected insulation resistance normalized to $40^\circ\text{C}$
• $R_T$ = Measured insulation resistance at field temperature $T$ ($^\circ\text{C}$)
• $K_T$ = Temperature correction factor
• $T$ = Winding temperature at time of test ($^\circ\text{C}$)

The 10°C Resistance Halving Rule: Insulation resistance halves for every $10^\circ\text{C}$ increase in winding temperature above $40^\circ\text{C}$, and doubles for every $10^\circ\text{C}$ decrease below $40^\circ\text{C}$.

Calculation Example: A megohmmeter test on a 600 V motor just taken offline at $70^\circ\text{C}$ yields a raw reading of $15\text{ M}\Omega$.

• Temperature delta: $70^\circ\text{C} - 40^\circ\text{C} = 30^\circ\text{C}$ (three 10°C increments).
• $K_T = (0.5)^{\frac{40 - 70}{10}} = (0.5)^{-3} = 2^3 = 8$.
• Normalized resistance: $R_{40} = 15\text{ M}\Omega \times 8 = 120\text{ M}\Omega$.
• While $15\text{ M}\Omega$ at $70^\circ\text{C}$ might appear questionable to an inexperienced electrician, its normalized value of $120\text{ M}\Omega$ at $40^\circ\text{C}$ proves the winding insulation is in excellent condition.

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7. Polarization Index (PI) & Dielectric Absorption Ratio (DAR) Diagnostics

When a high DC test voltage is applied to a motor winding, total current flowing to ground consists of three distinct components:

$$I_{\text{total}}(t) = I_{\text{capacitive}}(t) + I_{\text{absorption}}(t) + I_{\text{leakage}}$$

   Current
     ^
     |  I_total = I_capacitive + I_absorption + I_leakage
     |  * 
     |   *   [ I_capacitive ] (Decays to 0 in seconds)
     |    * 
     |     * * * * *   [ I_absorption ] (Decays over 10 minutes)
     |              * * * * * * * * * * * * * * *
     |─────────────────────────────────────────── [ I_leakage ] (Constant conduction current)
   0 +─────────────────────────────────────────────────> Time
     0 sec                       1 min               10 min

1. Capacitive Charging Current ($I_c$): Charges the physical capacitance between the winding and the grounded frame. It starts at a maximum and decays to zero within seconds.
2. Dielectric Absorption Current ($I_a$): Current resulting from molecular polarization within the insulating material. In healthy, dry insulation, it decays slowly over 10 minutes.
3. Conduction / Leakage Current ($I_l$): Steady-state current that passes through the body of the insulation and over surface contamination to ground. It remains constant over time.

In clean, dry insulation, as absorption current decays over time, the total current drops, causing the calculated resistance ($R = V/I$) to climb continuously throughout a 10-minute test. If insulation is contaminated with moisture, carbon dust, or oil, leakage current dominates immediately; resistance remains flat or drops.

Dielectric Absorption Ratio (DAR)

The Dielectric Absorption Ratio is the ratio of the insulation resistance reading at 60 seconds to the reading at 30 seconds:

$$\text{DAR} = \frac{R_{\text{60 seconds}}}{R_{\text{30 seconds}}}$$

• DAR < 1.0: Dangerous / Failure imminent.
• DAR = 1.0 to 1.25: Questionable condition (moisture or contamination present).
• DAR = 1.4 to 1.6: Good condition.
• DAR > 1.6: Excellent condition.

Polarization Index (PI)

The Polarization Index is the ratio of the insulation resistance reading at 10 minutes to the reading at 1 minute:

$$\text{PI} = \frac{R_{\text{10 minutes}}}{R_{\text{1 minute}}}$$

• PI < 1.0: Dangerous / Insulation breakdown.
• PI = 1.0 to 1.9: Poor to Questionable. Winding is dirty, wet, or contaminated; requires cleaning and bake-out before energization.
• PI = 2.0 to 4.0: Good. Universal industry standard benchmark for acceptable insulation integrity.
• PI > 4.0: Excellent. Clean, dry, modern synthetic insulation system.
• Exception Note: For modern epoxy-impregnated windings, if the 1-minute insulation resistance is extraordinarily high (e.g., > 5000 M$\Omega$), the leakage current is below the meter's microamp detection threshold, and the calculated PI may be artificially low without indicating a defect.

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8. CSA Z462 High-Voltage Testing Safety & Capacitive Discharge Protocols

Performing megohmmeter testing involves applying 1000 V to 5000 VDC to de-energized electrical machinery. Under CSA Z462 Workplace Electrical Safety, strict safety procedures must be enforced:

1. Lockout/Tagout & Zero-Energy State: The motor must be completely disconnected from all supply conductors (MCC breaker locked out and verified 0.0 V using live-dead-live testing).
2. Capacitive Stored Energy Hazard: A motor stator winding possesses significant capacitance (often $0.05\ \mu\text{F}$ to $0.5\ \mu\text{F}$). Under a 2500 VDC test, the winding stores dangerous, potentially lethal electrical energy: $$E = \frac{1}{2} C V^2$$
3. Mandatory Discharge Protocol:
   • Never touch motor terminals or disconnect megohmmeter test leads immediately after releasing the test button.
   • Modern digital megohmmeters have an internal automatic discharge circuit. Leave the test leads connected until the instrument's display reads 0 VDC.
   • Apply a physical, insulated discharge grounding jumper connected between the motor frame and the winding leads.
   • The 4x Rule: Under CSA Z462 and IEEE 43, the grounding jumper must remain connected to the winding for at least four times the duration of the applied voltage (e.g., minimum 4 minutes after a 1-minute test, or minimum 40 minutes after a 10-minute PI test) to bleed off deep dielectric absorption charge.

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9. Concrete Industrial Troubleshooting Scenario: Flood-Damaged 250 HP Boiler Feed Pump Motor

Facility Background & Problem Statement

During a spring thaw flooding event at a pulp and paper mill in Prince George, BC, a water main rupture submerged the basement pump room. A 250 HP, 575 V, 3-phase, 4-pole, 1780 RPM TEFC boiler feedwater pump motor was submerged in 1 meter of muddy water for 14 hours. After the room was pumped dry, plant operations requested an immediate emergency re-energization to prevent a mill-wide steam shutdown.

Diagnostic Field Evaluation

1. Pre-Test Safety Isolation: Electrician executes LOTO on MCC Bucket 3B-2, verifies 0 V using the live-dead-live protocol, and disconnects the line cables at the motor terminal box.
2. Winding Resistance Balance Check:
   • A four-wire DLRO measures phase-to-phase resistance:
     • $T1-T2 = 0.0842\ \Omega$
     • $T2-T3 = 0.0846\ \Omega$
     • $T3-T1 = 0.0841\ \Omega$
     • Calculated unbalance: $0.35%$ (well within the 2% allowable limit, confirming no broken turns or phase-to-phase shorts).
3. Insulation Resistance & PI Testing (1000 VDC Megohmmeter):
   • Ambient temperature in the pump room: $20^\circ\text{C}$.
   • 30-second reading: $0.85\text{ M}\Omega$
   • 1-minute reading ($R_{\text{1min}}$): $0.92\text{ M}\Omega$
   • 10-minute reading ($R_{\text{10min}}$): $1.02\text{ M}\Omega$
   • Normalized resistance at $40^\circ\text{C}$: $$K_T = (0.5)^{\frac{40 - 20}{10}} = (0.5)^2 = 0.25 \implies R_{40} = 0.92\text{ M}\Omega \times 0.25 = 0.23\text{ M}\Omega$$
   • Polarization Index: $$\text{PI} = \frac{1.02\text{ M}\Omega}{0.92\text{ M}\Omega} = 1.11$$
   • Dielectric Absorption Ratio: $$\text{DAR} = \frac{0.92}{0.85} = 1.08$$
4. Diagnostic Analysis:
   • The normalized insulation resistance ($0.23\text{ M}\Omega$) fails both the classical $1.6\text{ M}\Omega$ rule and the IEEE 43 minimum $5\text{ M}\Omega$ threshold.
   • The flat PI of 1.11 and DAR of 1.08 prove that the ground-wall insulation is heavily contaminated with trapped conductive water and silt. If energized across 575 V, the motor will suffer immediate catastrophic phase-to-ground flashover, destroying the stator core laminations.
5. Corrective Recovery Protocol:
   • Electrician rejects the immediate start request, citing CSA Z462 and IEEE 43 standards.
   • The motor is decoupled, removed from the pump room, and transported to the facility electrical maintenance shop.
   • End bells are disassembled, bearings flushed of contaminated grease, and the stator is thoroughly washed with deionized water and approved non-conductive solvent.
   • The stator is placed in a thermostatically controlled drying oven at $95^\circ\text{C}$ ($203^\circ\text{F}$) for 36 hours to evaporate trapped internal moisture without boiling water inside the slot insulation.
6. Post-Drying Verification:
   • After cooling to $20^\circ\text{C}$, the 1000 VDC megohmmeter test is repeated:
     • 1-minute reading: $185\text{ M}\Omega$
     • 10-minute reading: $560\text{ M}\Omega$
     • Normalized $R_{40}$: $185\text{ M}\Omega \times 0.25 = 46.25\text{ M}\Omega$ (exceeds $5\text{ M}\Omega$ requirement).
     • Polarization Index: $$\text{PI} = \frac{560\text{ M}\Omega}{185\text{ M}\Omega} = 3.03 \quad (\text{Exceeds 2.0 good threshold})$$
   • Bearings were repacked with synthetic grease, the motor was reinstalled, laser aligned, and returned to production, avoiding a $120,000 replacement motor cost.