Joy 600128-0735 Historical Rewind – 250 HP 950 V
Reference only. This low-voltage motor is outside our current service scope. TEMISA accepts medium- and high-voltage motors only.
In short
The 600128-0735 is a 250 HP, 950 V, 1,775 rpm cutter motor on frame 20B350J. TEMISA rewound one in March 2026 for an underground mine in Mexico: it arrived grounded at 0.03 MΩ and left at 6,700 MΩ, PI 7.94, 0% surge unbalance, with new form-wound Class H coils, restored bearing fits and a balanced rotor.
Joy 600128-0735 nameplate data
| Part number | 600128-0735 |
|---|---|
| Power | 250 HP |
| Voltage | 950 V |
| Current | 145 A |
| Speed | 1,775 rpm |
| Frequency | 60 Hz |
| Frame | 20B350J |
Application
Which continuous miners use the Joy 600128-0735?
A 250 HP, 950 V cutter motor on the same 20B350J frame used by other Joy 600128-series cutter motors. Confirm the application against your machine's parts book.
Source: TEMISA technical report TMS-CL-RE-02 Rev. 5, work order 2878, March 2026.
Underground mine, Mexico · March 2026
As received
- Insulation resistance 0.03 MΩ at 70 VDC: winding grounded, out of IEEE Std 43 limits.
- Phase resistance unbalance 1.3%: within IEEE Std 1415.
- Drive-end bearing housing fit out of ANSI/EASA AR100 tolerance.
- Both bearings damaged (NU 217 EC drive end, 6315/C3 opposite drive end).
- Rotor growler test: no open bars. Shaft: no deflection.
Work performed
What we did
- Stator rewound with new form-wound coils, Class H insulation.
- Dehydration, insulating varnish and controlled oven cure.
- Drive-end housing fit restored.
- New bearings induction-mounted and lubricated; new seals.
- Rotor dynamically balanced.
- Static and dynamic tests recorded before release.
Recorded results
As received vs. as released
Insulation resistance
As received
0.03 MΩ
at 70 VDC · grounded
Released
6,700 MΩ
at 510 VDC · PI 7.94
Rotor unbalance (A / C)
As received
20.0 / 31.0 g
initial
Released
2.0 / 2.0 g
final
Phase resistance unbalance
As received
1.3%
as received
Released
0.0%
116.2 mΩ × 3
Surge test, line to line
As received
—
winding grounded
Released
0%
at 3,930 V, all phases
Source: TEMISA report TMS-CL-RE-02 Rev. 5, work order 2878, March 2026.
Final test results, as recorded
| Phase resistance | 116.2 / 116.2 / 116.2 mΩ — 0.0% unbalance |
|---|---|
| Insulation resistance, 1 min at 510 VDC | 6,700 MΩ |
| Polarization index / DAR | 7.94 / 1.89 |
| Step-voltage hi-pot, final step | 5,103 VDC — 7,980 MΩ, 0.640 µA leakage |
| Surge test at 3,930 V | EAR L-L 0% on all three phases |
| RTDs (3) | 108.2 / 108.4 / 108.8 Ω at 21–22 °C |
| Rotor balance (A / C planes) | 20.0 g / 31.0 g initial → 2.0 g / 2.0 g final |
| Run test | 60 min energized; vibration 0.04 in/s max. |
Customer name withheld.
Historical process reference. These tables are not a current offer for this low-voltage model.
Scope of work
Documented repair process: winding and enclosure
| What we upgrade | What we never change |
|---|---|
| Stator rewound with new form-wound coils | Explosion-proof enclosure |
| Class H insulation system | Flame-path surfaces and their dimensions |
| Varnish treatment with dehydration and controlled oven cure | Lead entrances |
| Bearing fits restored to ANSI/EASA AR100 tolerances | Mounting and shaft dimensions |
| New bearings, induction-mounted, and new seals | Nameplate rating: HP, voltage and speed stay as built |
| Rotor dynamically balanced | |
| Temperature sensors (RTDs) tested |
Enclosure dimensions are not modified. Before a rebuilt explosion-proof motor goes back underground, the mine's qualified electrical person inspects it, as MSHA regulations require.
In our shop
What happens to your motor at TEMISA
1Teardown and diagnosis
The failed winding is exposed and documented before anything is quoted.
2Form-wound coils
New coils are formed and taped in the shop; the core is checked first.
3Varnish and oven cure
The winding is dehydrated, varnished and cured in a controlled oven.
4Dynamic balance
The rotor is balanced and the residual unbalance is recorded.
5Release tests
Static and dynamic tests are recorded before the motor ships.
Photos taken at the TEMISA shop. They show the process, not a specific customer motor.
Release tests
Tests recorded for the historical Joy repair
| Test | Standard | Acceptance |
|---|---|---|
| Winding resistance, phase to phase | IEEE Std 1415 | Unbalance < 3% |
| Insulation resistance, 1 min | IEEE Std 43 | > 100 MΩ |
| Polarization index and dielectric absorption | IEEE Std 43 | PI > 2.0 · DAR > 1.5 |
| Step-voltage DC high-potential | IEEE Std 95 | > 100 MΩ, leakage < 1 mA |
| Surge comparison (turn-to-turn) | IEEE Std 522 | EAR L-L < 3% · P-P < 10% |
| Core loop test with thermography | Shop procedure | Uniform core temperature |
| Rotor growler test | Shop procedure | No open bars |
| Dynamic balance of rotor | ISO 21940 | Residual unbalance recorded |
| 60-minute run test: current, temperature, vibration | Shop procedure | Vibration < 0.11 in/s |
Other Joy cutter motors
Have a different motor above 1,000 V?
Check its nameplate and request a scope review through our medium- and high-voltage enquiry form.
Medium/high-voltage enquiries