LTi Synchronous Motor LST/LSH Replacement Selection Guide

LTi Synchronous Motor LST/LSH Replacement Selection Guide

Overview of LT Synchronous Motor Series

LT (LTi DRiVES) synchronous servo motors are divided into two series: LST and LSH, covering a continuous torque range from 0.1 Nm to 115 Nm. They are widely used in machine tools, packaging, printing, robots, automated production lines, and other applications that require high dynamic response and precise position control. The LST series adopts conventional winding technology and is a 6-pole synchronous servo motor suitable for applications with speeds up to 9000 rpm. It has high overload capacity and optimized moment of inertia. The LSH series provides higher torque density under the same chassis size, suitable for scenarios that require greater torque but limited installation space.

The machine base numbers range from 037, 050, 074, 097, 127, 158, 190 to 220, and the numbers represent the measured dimensions of the motor (in millimeters), not the flange dimensions. Each machine base has different overall lengths (2, 3, 4, 5) and rated speeds (30 corresponds to 3000 rpm, 45 corresponds to 4500 rpm). The DC bus voltage of the controller can be selected as 320 V or 560 V, which directly affects the rated current and back electromotive force constant of the motor. For example, LST-127-2-30-560 represents a 127 machine base, length 2, rated speed of 3000 rpm, and DC bus 560 V.

The complete format of the order code is: LSX-074-1-30-560/Options. Among them, LSX represents LST or LSH; 074 is the edge measurement dimension; 1 is the overall length; 30 is the rated speed multiplied by 100; 560 is the DC bus voltage of the controller; After the slash is the option code, such as T0, T1, T4, B, P, X, K, S4, 1R, V, W, etc. The standard configuration includes a smooth shaft (keyless), a 1-pole rotary transformer, IP64 protection (excluding flanges), IP54 overall protection, direct output plug, and dual basic insulation. Common options include: T0 thermal protection constant temperature switch, T1 dual basic insulation DIN-PTC (standard), T4 KTY84-130, B 24 VDC holding brake, P keyway, X customized design, K 1-meter cable, S4 rotatable plug, 1R 1-pole rotary transformer, V IP65 without radial seal, W IP65 with radial seal (length increased by about 10mm).

Technical data and selection points

When selecting, the first step is to determine the continuous torque, peak torque, and maximum speed required for the load. Taking the LST-127 series as an example, at a rated speed of 3000 rpm on a 560 V DC bus, the rated torque for different lengths is as follows: length 1 is 5.7 Nm, length 2 is 8.8 Nm, length 3 is 11.0 Nm, length 4 is 14.0 Nm, and length 5 is 17.0 Nm. The locked rotor torque is 6.6, 10.5, 13.5, 17.0, and 22.0 Nm, respectively. The peak torque can reach 19.8, 32, 41, 51, and 66 Nm. The rated current ranges from 4.0 A to 13.0 A. Users need to choose the appropriate length based on the continuous torque and acceleration torque of the actual load, while leaving sufficient overload margin.

For the LST-158 series, at 560 V and 3000 rpm, the rated torque for lengths 1 to 5 is 13.0, 17.0, 19.0, 24.0, 26.0 Nm, the locked rotor torque is 13.5, 19.0, 22.0, 29.0, 35.0 Nm, and the peak torque is 47, 67, 77, 102, 105 Nm. The LST-190 series provides rated torque of 21, 23, and 26 Nm, with peak torque of 81, 96, and 120 Nm. The LST-220 series provides rated torque of 30, 50, 60, and 50 Nm, with peak torque of 120, 204, 279, and 345 Nm, suitable for high-power applications.

When selecting, attention should also be paid to the DC bus voltage. The 320 V system is typically used for low-voltage servo drives, while the 560 V system is used for drives powered by standard 400 V AC. If the original motor uses 320 V, it cannot be directly replaced with a 560 V motor unless the driver supports it and the parameters are reset. The rated speed should also be matched, as motors at 3000 rpm and 4500 rpm have different currents at the same torque. In addition, the back electromotive force constant Ke, torque constant Kt, winding resistance, and inductance of the motor all affect the current loop and speed loop parameters of the driver, and usually require recalibration after replacement.

Encoder Options and Compatibility

LT synchronous motors can be equipped with multiple encoders to meet different precision and interface requirements. The standard configuration is a 1-pole rotary transformer (Resolver) with an accuracy of approximately ± 10 arcminutes. Optional 3-pole or 5-pole rotation with higher accuracy, reaching ± 5 arcminutes and ± 5 arcminutes respectively. For applications that require absolute value positions, multi turn absolute value encoders such as EON 1325 SSI (G3), ECN 1313 SSI (G5), SRS 50 (G6.1S1), SRM 50 (G6.1M1), SKS 36 (G6.2S1), SKM 36 (G6.2M1), ECN 1313 Endat 2.1 (G12.1S1), ECN 1325 Endat 2.1 (G12.1M1), ECN 1113 Endat 2.1 (G12.2S1), and EON 1125 Endat 2.1 can be selected. (G12.2M1) and others.

The system accuracy of different encoders varies significantly. The end-to-end absolute accuracy of the Resolver is about ± 10 arcminutes, while the G3/G5 encoder can achieve ± 20 arcminutes, and the G12 series is even better. It should be noted that some encoders (such as G6.2, G12.2) are not suitable for CDE3000 and CDF3000 drivers, and driver compatibility must be checked when selecting. Encoder cables must use shielded cables, with both ends of the shielding layer grounded. Differential signals A, B, R or CLK, DATA must be twisted in pairs. If using both rotary and TTL/SSI encoders, an independent 5V power supply needs to be provided for the encoder, and the maximum current should be 150 mA.