VFD vs Servo Drive: Key Differences
A side-by-side comparison of VFD and servo drive motor type, feedback, dynamic response, overload rating, cost, and applications for industrial engineers.
The Siemens 1FK7103-2AF71-1QA0 is a SIMOTICS S 1FK7-CT synchronous servo motor rated at 4.4 kW with a 36 Nm standstill torque at 3000 rpm nominal speed. It runs from a 600 V DC bus, mounts in IM B5 (IM V1, IM V3) configuration with Flange 1, and carries a Drive-CLiQ absolute single-turn 20-bit encoder (AS20DQI) with IP64 protection and no holding brake.
This AF71 winding trades torque constant for a higher 3000 rpm nominal speed and 2500 rpm optimum speed, compared with a lower-speed winding available in the same 1FK7103 frame, which makes it the better fit where the application needs faster point-to-point moves rather than maximum torque per amp. Without a holding brake, the servo drive or an external brake must hold the axis at standstill; the same frame is also offered with an integrated brake for vertical or overhung-load axes. At 11.5 A rated current and a 2.4 mH rotating field inductance, this winding has a 27.00 ms electrical time constant, which supports fast current-loop response.
| Rated speed (100 K) | 3,000 rpm |
|---|---|
| Number of poles | 8 |
| Rated torque (100 K) | 14.0 Nm |
| Rated current | 11.5 A |
| Static torque (60 K) | 30.00 Nm |
| Static torque (100 K) | 36.00 Nm |
| Stall current (60 K) | 21.00 A |
| Stall current (100 K) | 26.00 A |
| Moment of inertia | 104.000 kgcm² |
| Efficiency | 93.0 % |
| Torque constant | 1.39 Nm/A |
|---|---|
| Voltage constant at 20º C | 89.5 V/1000*min¯¹ |
| Winding resistance at 20º C | 0.09 Ω |
| Rotating field inductance | 2.4 mH |
| Electrical time constant | 27.00 ms |
| Mechanical time constant | 1.46 ms |
| Thermal time constant | 65 min |
| Shaft torsional stiffness | 148,000 Nm/rad |
| Net weight of the motor | 28.5 kg Permanent-magnet synchronous |
| Motor type | motor Compact |
|---|---|
| Shaft height | 100 |
| Cooling | Natural cooling |
| Radial runout tolerance | 0.050 mm |
| Concentricity tolerance | 0.10 mm |
| Axial runout tolerance | 0.10 mm |
| Vibration severity grade | Grade A |
| Connector size | M40 |
| Degree of protection | IP64 |
| Design acc. to Code I | IM B5 (IM V1, IM V3) |
| Temperature monitoring | Pt1000 temperature sensor |
| Electrical connectors | Connectors for signals and power rotatable |
| Color of the housing | Standard (Anthracite RAL 7016) |
| Holding brake | without holding brake |
| Shaft end | Feather key |
| Encoder system | Encoder AS20DQI: absolute encoder single-turn 20 bits |
| Part number | 1FK7103-2AF71-1QA0 |
|---|---|
| Brand | Siemens |
| Condition | New, factory sealed |
| Source | Siemens and its authorised distributors |
| Warranty | Manufacturer warranty |
| Optimum speed | 2,500 rpm |
|---|---|
| Optimum power | 5.4 kW |
| Max. permissible speed (mech.) | 5,000 rpm |
|---|---|
| Max. permissible speed (inverter) | 5,000 rpm |
| Maximum torque | 108.0 Nm |
| Maximum current | 84.0 A |
| Rated inverter current | 30 A |
|---|---|
| Maximum inverter current | 90 A |
| Maximum torque | 108.00 Nm |
| Page 1 of 1 | Generated Sun Nov 1 02:25:41 CET 2026 |
| Shipping weight | 30.501 kg |
|---|---|
| Ships from | Türkiye |
| Dispatch | — |
| Stock | On request |
Source: manufacturer data · Last verified: 01 Nov 2026
No documents are on file for this part yet.
Ask us for the datasheetThe rated current of 1FK7103-2AF71-1QA0 is 11.5 A.
The rated motor power of 1FK7103-2AF71-1QA0 is 4.4 kW.
The tariff (HS) code on file for 1FK7103-2AF71-1QA0 is 85015220.
1FK7103-2AF71-1QA0 ships from Türkiye. Shipping calculated at checkout · import duties and taxes paid on arrival.
A side-by-side comparison of VFD and servo drive motor type, feedback, dynamic response, overload rating, cost, and applications for industrial engineers.
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