ST570S Motor Protection Controller

The ST570S Motor Protection Controller is an advanced all-in-one device designed for low-voltage motors operating at rated frequencies of 50/60Hz and voltages up to AC660V/AC690V. Integrating protection, measurement, control, management, and communication functions, it works seamlessly with contactors, soft starters, variable frequency drives (VFDs), and circuit breakers to deliver comprehensive motor control solutions — making it the ideal terminal unit for intelligent MCC or DCS systems.

Key Features

• Modular design: base module + dedicated current transformer + display module + expansion modules
• Compact structure, small footprint — fits directly into 1/4 modular and larger drawer cabinets
• Multiple motor starting control schemes
• Suitable for explosive environments (increased safety type "e" per GB/T 3836.3-2021)
• Wide industry application: power generation, oil & gas, petrochemical, metallurgy, coal, paper, rail transit

Compliance Standards

• GB/T 14048.4 — Low-voltage switchgear and controlgear
• GB/T 14598.303 — Digital motor comprehensive protection general technical requirements
• GB/T 3836.3-2021 — Explosive atmospheres, increased safety type "e"

Technical Specifications

Environmental Conditions

• Operating Temperature: -10°C to +55°C
• Storage Temperature: -25°C to +70°C
• Relative Humidity: 5%–95% (no condensation or icing)
• Atmospheric Pressure: 80–110 kPa
• Altitude: <3,000 m
• Pollution Degree: Class 3
• Body Protection: IP20 | Panel Protection: IP54

Auxiliary Power Supply

• Voltage Range: 85–264VAC/50Hz; 110VDC / 220VDC
• Power Consumption: <5W / 10VA
• Surge Current: <20A
• Power Interruption Tolerance: ≥500ms

Current Circuit

• Rated Parameters: 1A (0.2–1A), 5A (0.5–5A), 25A (2.5–25A), 100A (10–100A), 160A (16–160A), 400A (40–400A)
• External CT options for motors >400A: 500A (150–500A), 820A (250–820A)
• Overload Capacity: 2× rated current continuous; 10× rated current for 10s; 40× rated current for 1s
• Rated Frequency: 50/60Hz

Voltage Circuit

• Rated Parameters: 380V, 660V
• Overload Capacity: 1.2× rated voltage continuous; 1.4× rated voltage for 10s
• Power Consumption: <1VA/phase
• Rated Frequency: 50/60Hz

Protection Functions

Thermal Overload Protection

Prevents motor damage caused by overload-induced overheating. The protection activates after motor start, using the ratio of equivalent current to rated current as the trigger criterion. The thermal model accounts for both positive and negative sequence current heating effects, following inverse-time characteristics. Two reset modes are available:

• Auto Reset: Automatically clears the fault once thermal capacity drops below the reset threshold — no manual intervention required.
• Manual Reset: Requires manual operator reset after thermal capacity drops below the reset threshold before the motor can restart.