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Two-phase hybrid stepper motor series

Manufacturer catalogue image · Series illustration

Stepper motors

Two-phase hybrid stepper motor series

SYN-TRON logoSYN-TRONView manufacturer →
Step Angle
1.8°
Example Model
42BYG250BK-0151
Example Phase Current
1.5 A
Example Holding Torque
0.43 N·m

Catalogue series · Exact configuration and availability confirmed by the manufacturer.

Two-phase steppers: a 42(K) replacement starts with the shaft arrangement

A two-phase frame size is not a complete replacement specification. In SYNTRON’s July 2026 42(K) manual, each A, B and C body is offered with a single shaft or a shaft at both ends. The paired versions share the listed electrical ratings, but the rear shaft changes the space and mechanical interface the machine must accommodate.

Read SASSML versus BASSML before ordering

Single shaft: SASSML

The listed 42BYG250AK, BK and CK single-shaft versions end in SASSML-0151. Their front shaft is 5 mm in diameter and extends 24 mm; the drawing gives a 42.3 mm square face, 22 mm register and four M3 holes on a 31 ±0.1 mm square pattern. Match the register and shaft tolerances on the approved drawing, not just the nominal frame label.

Double shaft: BASSML

The corresponding BASSML-0151 versions add a 5 mm rear shaft extending 10 mm. The body lengths remain 34, 40 and 48 mm for A, B and C. This is a mechanical extension, not evidence that an encoder is included or that the motor operates closed loop. Check the rear attachment and guarding envelope before substituting a double-shaft motor.

A special version needs its own drawing

The naming key allows shaft shape, length and connection variations and identifies Ver*.* as a custom version. The selected table uses four-lead motors; the broader key also describes an eight-lead option. Do not apply the four-lead wiring diagram to a differently terminated custom motor merely because its frame and current appear similar.

A, B and C body choices at the same 1.5 A phase current

The data apply to 42BYG250AK/BK/CK with the SASSML-0151 or BASSML-0151 suffixes listed in the manual. The no-load starting-frequency column is measured at 24 V DC in half-step operation; it is not a loaded start-speed specification.

BodyHolding torqueInductance / resistanceInertia / massLength LNo-load start
A 0.23 N·m 2.1 mH / 1.3 Ω 38 g·cm² / 0.21 kg 34 mm 1.6 kHz
B 0.43 N·m 5.0 mH / 2.1 Ω 57 g·cm² / 0.23 kg 40 mm 1.5 kHz
C 0.54 N·m 3.85 mH / 2.0 Ω 82 g·cm² / 0.36 kg 48 mm 1.5 kHz

Make the loaded move part of the acceptance test

Starting frequency and running torque answer different questions

At a 0.9° half-step setting there are 400 commanded steps per revolution. Thus 1.5 kHz corresponds geometrically to 225 r/min, but the catalogue’s start figure is specifically no-load. A machine carrying inertia or friction may need an acceleration ramp instead of an instantaneous start at that command rate. State the actual load and required move time.

Use each body’s own curve

The A, B and C torque plots use 24 V DC and 0.9° steps and show torque declining with frequency. Their stationary holding values do not define running torque across the speed range. The B motor also has more inductance than C despite less holding torque. Select from the relevant curve and confirm the driver settings rather than extrapolating performance from body length or current alone.

Keep the two winding pairs intact

For the standard four-lead version, the manual shows red A+, blue A−, green B+ and black B−. It explicitly warns against incorrect phase connections. Record those winding pairs and the actual driver terminal assignments during replacement. The listed typical drivers are SD-20403 and SD-20504; obtain the exact revision and current-setting convention with the offer.

Check alignment and thermal duty in the real mounting

The manufacturer requires front-register location and motor/load shaft concentricity, warning that misalignment can bend or break the shaft. It specifies 0 to 50 °C operating ambient, humidity below 85% RH and class B insulation. Include coupling, mounting heat path, move/dwell cycle and ambient in the acceptance setup; successful unloaded bench rotation is not the whole test.

CATALOGUE OVERVIEW

About this motor series

SYNTRON offers two-phase hybrid stepper motors for incremental positioning. The catalogue includes 28, 35, 39, 42, 56, 86 and 110 frame families with model-specific current, resistance and holding-torque tables. The listed step angle is 1.8 degrees.

As a selection example, the 42BYG250BK-0151 is listed at 1.5 A and 0.43 N·m holding torque. Holding torque describes the energized stationary condition, not available torque at running speed. Select the driver supply, acceleration and load from the torque-speed curve for the exact winding.

Model / series reference: Two-phase hybrid

Published specifications

Specifications describe a series range; confirm which ratings apply together to the quoted model.

Step Angle
1.8°
Example Model
42BYG250BK-0151
Example Phase Current
1.5 A
Example Holding Torque
0.43 N·m
Power
Confirm configuration
Voltage
Confirm supply
Speed
Model dependent
Catalogue Type
Product series

Confirm mounting and shaft dimensions against the drawing for the quoted configuration.

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