Pacific Scientific SCE900 Servo Drive Complete Guide

Motor PTC thermal protection: PTC and PTC RTN terminals are connected to the built-in positive temperature coefficient thermistor or normally closed temperature control switch of the motor. When the resistance is greater than 6.2k Ω, the driver reports a "motor overheating" fault.

5.3 Command I/O connector J4 (25 pin D-sub)

Analog command input (J4-1,2): differential input, full range ± 13.5V, maximum single ended range ± 21V, input impedance>50k Ω, adjustable offset and low-pass filtering bandwidth through software.

DAC monitoring output (J4-3,4): ± 5V analog output, resolution 10V/256 ≈ 0.039V, can be mapped to 28 internal variables such as speed, current, position error, bus voltage, etc., used for oscilloscope diagnosis.

Enable input (J4-6): Low level active, internal pull-up 3.3k Ω, minimum driving capacity 5mA, maximum external voltage 30V. Equipped with 2ms low-pass filtering and programmable logic threshold (5V or 12V pull-up).

Bidirectional digital I/O (BDIO 1-6) (J4-7 to 12): programmable as input or output. As an output, it is an open collector electrode with a withstand voltage of 30V and a current capacity of 100mA for BDIO1-5 and 200mA for BDIO6 (non short-circuit protection). As input, it has a 20 μ s filtering and 1V hysteresis. Factory default functions: BDIO1=fault reset, BDIO2=forward limit (CW Inhibit), BDIO3=reverse limit (CCW Inhibit), BDIO4=unmapped, BDIO5=brake output (engaged when driver enabled), BDIO6=fault output.

I/O common terminal (J4-5, 13, 18): signal ground.

Encoder simulation output (J4-14 to 17,19,20): differential TTL signal, A、A̅、B、B̅、Z、Z̅， Generated from the position of the Resolver, simulating a photoelectric encoder. The output resolution can be programmed into 16 levels (binary: 128/256/.../16384 PPR; Decimal: 125/250/ ../16000 PPR）。 Using 26LS31 driver, with a maximum load of ± 20mA, it can drive 10 RS-422 receivers and output ground short-circuit protection.

Encoder input (J4-21 to 24): Differential RS-422 compatible (26LS32), capable of receiving orthogonal encoders, step/direction or addition/subtraction pulse signals. The maximum input frequency is 800kHz (fast decoding mode). Supports single ended TTL signals (requires an external pull-up resistor). The decoding mode is selected through the EncMode parameter and has programmable 4:1, 8:1, or 16:1 filtering deceleration modes.

+5V auxiliary output (J4-25, reference ground J4-18): 5V ± 5%, maximum 200mA, short circuit protection, can be used to power external encoders or sensors.

Rotary Transformer Feedback System

The SCE900 series comes standard with Resolver feedback, allowing for high-precision and highly reliable position and velocity closed-loop without the need for a photoelectric encoder. The excitation frequency of the Resolver is 6510.42Hz, the maximum tracking speed is>48600 rpm, the maximum recommended speed is 25 krpm, and the maximum tracking acceleration is 16 × 10 ^ 6 rpm/s. The maximum length of the Resolve cable is 50 meters. Noise level of speed feedback:<3 rpm RMS without filtering,<0.6 rpm RMS after single pole filtering at 150Hz,<0.06 rpm RMS after filtering at 10Hz. The typical value of DC accuracy is ± 0.01%, and the worst is ± 0.05%. This performance far exceeds traditional analog speed sensors.

Protection function and fault diagnosis

SCE900 integrates comprehensive protection circuits, and all faults are indicated in the form of flashing codes through a seven segment LED display screen (while extended fault codes can be read through software). The main protection functions include:

Output short circuit protection: phase to phase short circuit and phase to neutral point (ground) short circuit detection.

Motor overheating: monitored through PTC input.

Drive overheating: Power module heat sink temperature monitoring, automatically disabling output when exceeding threshold.

Bus overvoltage/undervoltage: The overvoltage threshold is adjustable, and undervoltage detection controls the power supply.

I ² t current limiting: Intelligent adjustment of continuous current limit based on heat sink temperature to prevent overheating of power devices.

Control power undervoltage.

+5V auxiliary output short circuit protection.

Processor watchdog malfunction.

After the fault occurs, the drive locks the fault state, disables the output stage, and activates the mappable fault output (BDIO6). The fault can be cleared by resetting the input (BDIO1) or re powering on the control power supply. Typical fault codes include: 1 flicker (speed feedback overspeed), 2 flicker (motor overheating), 3 flicker (driver overheating), 4 flicker (I ² t overcurrent), 7 flicker (output overcurrent or bus overvoltage), 8 flicker (brake chopper overload), 9 flicker (DSP detects bus overvoltage), etc.

CE compliant installation and EMC measures

To ensure compliance with the Low Voltage Directive (73/23/EEC) and the EMC Directive (89/336/EEC), the SCE900 series must comply with the following requirements during installation:

8.1 Grounding

Due to the leakage current to ground of the internal circuit filter of the driver being approximately 15mA, a dual PE line redundant connection must be used: J1 pin4 and J6 pin1 (both PE symbols) must be independently connected to the protective ground, and the connection point must be a permanent hard wire (plug-in connectors cannot be used). Cannot rely on residual current devices (RCD) as safety protection.