Home > Nema 51 3-Phase Stepper Motor
| Item | Specifications |
|---|---|
| Step Angle Accuracy | ±5% |
| Resistance Accuracy | ±10% |
| Inductance Accuracy | ±20% |
| Temperature Rise | 80°C Max. |
| Ambient Temperature | -20°C ~ +50°C |
| Insulation Resistance | 100MΩ Min. 500VDC |
| Dielectric Strength | 500V AC 1 minute |
| Allowable Radial Load | 0.02mm Max. (450g load) |
| Allowable Thrust Load | 0.08mm Max. (450g load) |
| Model | Step Angle (°) | Length (mm) | Voltage (V) | Current (A/phase) | Resistance (Ω/phase) | Inductance (mH/phase) | Holding Torque (N·m) | Rotor Inertia (g·cm²) | Leads | Weight (kg) |
| 130BYG350-230 | 1.2 | 230 | 7.8 | 6.5 | 1.2 | 16 | 30 | 28900 | 3 | 7 |
| 130BYG350-250 | 1.2 | 250 | 9.1 | 6.5 | 1.4 | 17 | 36 | 34000 | 3 | 8.5 |
| 130BYG350-290 | 1.2 | 283 | 10.4 | 6.5 | 1.6 | 21 | 50 | 43000 | 3 | 10 |
*These are representative models. We can manufacture products according to customer's requirements.
A NEMA 51 stepper motor is a 130mm hybrid stepper — the largest standard stepper frame. Ours are 3-phase: three windings driven through a 3-half-bridge driver, giving a 1.2° step angle (300 steps per revolution), smooth motion, and the highest holding torque in the stepper range. It is built for the heaviest stepper-driven axes.
A NEMA 51 stepper motor has a 130mm × 130mm faceplate. Body length runs 165mm to 205mm across our models, with a large keyed shaft. Full specs are in the table and the downloadable datasheet.
Our 130BYG350 range delivers holding torque from about 20 N·m on the 165mm body up to 25 N·m on the 205mm body — the top of the entire stepper range. Beyond this, more torque comes from a gearbox, or from moving to an AC servo for high torque at high speed.
A NEMA 51 needs a high-current 3-phase stepper driver. Rated current is around 6.0–8.0 A/phase, and a high bus voltage (80–110VDC) is required — this is the largest frame, with the highest winding inductance, so it needs the voltage to hold torque at speed. We supply a matched 3-phase driver set for the motor.
NEMA 51 is offered only as a 3-phase motor because at this frame size the smoothness and high-speed torque of a 3-phase design matter most. A 2-phase motor this large would vibrate heavily and hit resonance problems; the three-phase winding avoids that, which is why the largest hybrid steppers are built 3-phase.
Choose a NEMA 51 stepper when you need very high holding torque at low to moderate speed, open-loop, at lower cost than a servo. Choose an AC servo motor when you need that torque at high speed, with feedback and no lost steps. Our engineers can size either against your load — see the servo-motors range for the alternative.
The NEMA 51 stepper motor is the largest standard stepper frame, with a 130mm × 130mm faceplate. It is built only as a 3 phase motor: three windings give a smoother current waveform, low vibration, and the high-speed capability a frame this size needs. It runs at a 1.2° step angle (300 steps per revolution) and delivers the highest torque in the stepper range — it is the highest torque stepper motor we build, up to about 25 N·m. This is the motor for the heaviest stepper-driven axes in large CNC and industrial machines.
| Parameter | Specification |
|---|---|
| Frame Size | 130 × 130 mm |
| Step Angle | 1.2° (300 steps/rev) |
| Phase | 3-phase |
| Holding Torque | 20–25 N·m |
| Rated Current | 6.0–8.0 A/phase |
| Body Length | 165–205 mm (varies by model) |
| Drive | 3-phase driver (3 half-bridges) |
| Lead Wires | 3-wire |
At 130mm, a 2-phase winding would vibrate heavily and run into strong mid-speed resonance. The three-phase design solves that, which is why the largest hybrid steppers are made this way:
The motor needs a high-current 3-phase stepper driver, sized for 6–8 A per phase and a high bus voltage.
NEMA 51 is reserved for the very heaviest stepper-driven axes:
With a gearbox the same frame drives an extreme-torque, low-speed axis; a dual-shaft version adds a rear shaft for an encoder. Mounting brackets are available for machine integration.
NEMA 51 is the largest stepper frame, so there is no larger stepper. When an axis needs more than a NEMA 51 can give, the paths are:
| Need | Solution |
|---|---|
| More torque, low speed | Add a gearbox to the NEMA 51 |
| High torque at high speed | Move to an AC servo motor |
| A smaller 3-phase frame | Step down to NEMA 42 3-phase |
A NEMA 51 holds very high torque at low to moderate speed at lower cost than a servo. If the axis must run fast and heavy with feedback, an AC servo motor is the better answer. For a smaller 3-phase frame, see the NEMA 42 3-phase. Our engineers can size either against your load.
Cymotorix NEMA 51 3-phase stepper motors can be customized for OEM integration. As a NEMA 51 3-phase stepper motor manufacturer and supplier, we produce them to your specification. Common modifications include:
A NEMA 51 runs only on a high-current 3-phase stepper driver, which switches the three windings through three half-bridges. It will not run on a 2-phase driver. Rated current is around 6.0 to 8.0 A per phase, so a heavy-duty 3-phase driver is required. We supply a matched 3-phase driver set up for the motor if you want the pair tested together.
Recommended supply voltage is 80–110VDC. This is the largest frame, with the highest winding inductance, so a high bus voltage is essential to push current in fast and hold torque at speed. Set the driver's current limit to the motor's rated current so the windings don't overheat.
