BMS Series Brushless, Slotless Rotary Motor


Design Features

  • Slotless, brushless stator design provides zero cogging torque for unsurpassed velocity control
  • Smoother velocity than with standard DC brush-type motors with the advantage of reliable brushless technology
  • Standard NEMA frame sizes
  • Ultra-high resolution capability with amplified sine-wave encoder and multiplier
  • Follows the 2011/65/EU RoHS 2 Directive

Aerotech's BMS series brushless, slotless servomotors represent the ultimate in high-performance rotary motors. Available in standard NEMA frame sizes, these motors utilize a slotless stator design for superior velocity smoothness and control.

Featuring rare-earth magnets and a high pole-count rotor, the BMS series provides maximum torque and acceleration in a small package. Custom mechanical or electrical variations of the BMS can be engineered with minimal lead time.

Smoother than DC Motors

The BMS series motors can replace standard brushless or brush-type motors when superior velocity smoothness and control are required. DC brush-type motors have been popular in applications such as machine tool and scanning because of their smooth low-speed control. The BMS motors provide superior smoothness and have higher acceleration capability than a DC brush motor. Higher acceleration results in higher machine throughput and performance.

High Performance Design

The BMS series is unlike conventional brushless servomotors because it incorporates a totally slotless stator design that provides the ultimate in smooth velocity control. These motors are designed for applications requiring superior torque and stability performance. The unique design of the BMS series motors provides a closer inertia match with mechanical systems than comparable models. This means better stability and easier tuning.

Ultra-High Encoder Resolution

The BMS series motors can be equipped with a variety of encoder resolution options for any application. In addition to the standard RS-422 line driver output, an optional amplified sine-wave encoder can be used to provide ultra-high resolution. Aerotech offers encoder multipliers as an option for drives connected to the A3200 system, as well as external multiplier boxes. Resolutions as high as 1,000,000 counts per revolution are achievable.

Need help sizing your motor? Try Aerotech's Motor Sizer software to specify the ideal motor for your application.


BMS Series Specifications

Motor ModelUnitsBMS35BMS60BMS100BMS280BMS465
Winding Designation A A A A A
Performance Specifications(1,5)
Stall Torque, Continuous(2) N·m 0.27 0.33 0.56 1.60 2.86
oz·in 38.0 46.2 80.0 227.0 404.8
Peak Torque(3) N·m 1.07 1.31 2.26 6.41 11.43
oz·in 152.0 184.9 320.0 908.0 1619.2
Rated Speed rpm 4,000 4,000 3,000 3,000 2,000
Rated Power Output, Continuous W 96.0 112 133 381 457
Electrical Specifications(5)
BEMF Constant (Line-Line, Max) Vpk/krpm 12.9 19 40 57 79
Continuous Current, Stall(2) Apk 2.5 2.3 2.1 3.8 4.9
Arms 1.7 1.6 1.5 2.7 3.5
Peak Current, Stall(3) Apk 9.8 9.2 8.4 15.2 19.6
Arms 6.9 6.5 5.9 10.7 13.9
Torque Constant(4,8) N·m/Apk 0.11 0.14 0.27 0.42 0.58
oz·in/Apk 15.5 20.1 38.1 59.7 82.6
N·m/Arms 0.15 0.20 0.38 0.60 0.82
oz·in/Arms 21.9 28.4 53.9 84.5 116.8
Motor Constant(2,4) N·m/√W 0.046 0.050 0.076 0.179 0.280
oz·in/√W 6.52 7.02 10.74 25.34 39.70
Resistance, 25°C (Line-Line) Ω 5.8 8.4 12.9 5.7 4.4
Inductance (Line-Line) mH 1.7 1.30 2.40 1.10 0.87
Maximum Bus Voltage VDC 340 340 340 340 340
Thermal Resistance °C/W 2.21 1.73 1.35 0.93 0.72
Number of Poles - 8 8 8 14 14
Mechanical Specifications
Frame Size NEMA 17 23 23 34 34
Motor Weight kg 0.6 1.1 1.5 3.60 5.00
lb 1.3 2.4 3.3 7.9 11.0
Rotor Moment of Inertia kg·m2 1.96x10-5 1.96x10-5 3.71x10-5 4.66x10-4 9.28x10-4
oz·in·s2 0.0028 0.0028 0.0053 0.0660 0.1314
Max Radial Load N 45 89 89 178 178
lb 10 20 20 40 40
Max Axial Load N 45 89 89 89 89
lb 10 20 20 20 20
Standards   2011/65/EU RoHS 2 Directive
  1. Performance is dependent upon heat sink configuration, system cooling conditions, and ambient temperature.
  2. Values shown @ 75°C rise above a 25°C ambient temperature, with housed motor mounted to a 250 mm x 250 mm x 6 mm aluminum heat sink.
  3. Peak torque assumes correct rms current; consult Aerotech.
  4. Torque constant and motor constant specified at stall.
  5. All performance and electrical specifications ±10%.
  6. Maximum winding temperature is 100°C; thermistor trips at 100°C.
  7. Ambient operating temperature range 0°C - 25°C. Consult Aerotech for performance in elevated ambient temperatures.
  8. All Aerotech amplifiers are rated Apk; use torque constant in N·m/Apk when sizing.
  • Torque Speed Curves


  • NEMA 17 [BMS35]
  • NEMA 23 [BMS60, BMS100]
  • NEMA 34 [BMS280, BMS465]

Ordering Information

Ordering Example

BMS60 -A -D25 -E1000H -BK -HF -5

Ordering Options

SeriesMotor WindingConnectorsFeedbackBrakeCable TypeCable Length


-HF -xx

NEMA Brushless Slotless Rotary Servomotors

BMS35 NEMA17 Brushless slotless rotary servomotor
BMS60 NEMA23 Brushless slotless rotary servomotor
BMS100 NEMA23 Brushless slotless rotary servomotor
BMS280 NEMA34 Brushless slotless rotary servomotor
BMS465 NEMA34 Brushless slotless rotary servomotor

Motor Winding (Required)

-A Motor winding
-B Motor winding; not available for BMS35

Connectors (Required)

-MS Integral cable w/MS connector for Fbk and Mtr (-MS); not available for BMS35
-D25 Integral cable w/D25 Fbk and 4D Mtr (-D25); not available for BMS280 or BMS465
-D25-9D Integral cable w/D25 Fbk, 4D Mtr, and 9D Limit (-D25-9D); not available for BMS280 or BMS465
-D25-FLB Integral cable w/D25 Fbk, Fly Leads for Mtr, and 9D Limit (-D25-FLB); not available for BMS280 or BMS465
-D25-5DU Integral cable w/D25 Fbk, 5D Mtr, and 9D Limit (-D25-5DU); not available for BMS280 or BMS465
-D25-9D-CMS Integral cable w/D25 Fbk, 4D Mtr, and 9D Limit - CMS only (-D25-9D-CMS); not available for BMS280 or BMS465
-D25-4TS Integral cable w/D25 Fbk, 4TS Mtr, and 9D Limit (-D25-4TS); not available for BMS280 or BMS465

Feedback (Required)

-E1000H 1000 lines/rev TTL incremental encoder w/Hall tracks
-E2000H 2000 lines/rev TTL incremental encoder w/Hall tracks
-E2500H 2500 lines/rev TTL incremental encoder w/Hall tracks; not available for BMS35
-E5000H 5000 lines/rev TTL incremental encoder w/Hall tracks
-E1000ASH 1000 lines/rev 1 Vpp incremental encoder w/Hall tracks

Brake (Optional)

-BK Holding brake (-BK)

Cable Type (Optional)

-HF High flex cable; not available for BMS280 or BMS465

Cable Length (dm) (Optional)

-xx Cable length in decimeters (3.8 dm is default)

Note: Not available for BMS280 or BMS465.

Vacuum Preparation (Optional)

-VAC6 Vacuum preparation to 10-6 Torr

Accessories (Optional)

MC-HPD25-M Connector; HPD motor power mate
MC-DB25-F Connector; DB25 motor feedback mate
MCM-3 Connector; MS motor power mate
MCF-3 Connector; MS motor feedback mate

Note: Accessories are ordered as separate line items.