Product Overview

The ST570B3 Motor Protection Controller is designed for low-voltage motor applications rated at 50/60Hz and up to AC380V/AC400V. It integrates protection, measurement, control, management, and communication functions. Working in conjunction with contactors, soft starters, variable frequency drives, and circuit breakers, it enables multiple motor starting and control schemes to ensure safe motor operation. It is the ideal choice as a terminal unit for intelligent MCC or production DCS systems.

The series adopts a modular design, consisting of a main body and dedicated current transformers. It is compact, easy to install, and suitable for direct installation in 1/4 modular and larger drawer cabinets.

Widely applicable in power generation, petroleum, petrochemical, chemical, metallurgy, coal, paper, rail transit, and other industries.

Complies with GB/T 14048.4 (Low-voltage switchgear and controlgear – AC contactors and motor starters) and GB/T 14598.303 (General technical requirements for digital comprehensive motor protection devices).

Technical Specifications

2.1 Environmental Conditions

• Operating Temperature: -10 to +55°C
• Storage Temperature: -25 to +70°C
• Relative Humidity: 5–95% (no condensation or icing)
• Atmospheric Pressure: 80–106 kPa
• Altitude: <3000 m
• Pollution Degree: Level 3
• Protection Degree: IP20

2.2 Rated Parameters

Auxiliary Power Supply

• Power Range: 85–264 VAC / 90–300 VDC
• Power Consumption: <5W/10VA, Inrush Current 20A

Electromagnetic Compatibility (EMC)

Protection Functions

Thermal Overload Protection

Prevents motor damage from overload heating. Uses equivalent current vs. rated current ratio as the criterion, considering both positive and negative sequence thermal effects. Supports automatic and manual reset modes.

Blocking Protection

Protects against rotor stall during operation. Activates when the maximum phase current exceeds the set value, executing in definite-time mode.

tE Time Protection

Applicable to increased-safety explosion-proof motors under continuous operation. Complies with GB3836.3. The tE trip time must satisfy tETrip ≤ tE.

Start Timeout Protection

Prevents insulation damage from excessive start time. Activates if current exceeds the set value after the configured start timeout period.

Single-Phase Ground Protection

Calculates ground current from the vector sum of three-phase currents. Effective in TN distribution systems for detecting single-phase ground faults without an external ground CT.

Leakage Protection

Detects insulation degradation or non-direct ground faults. Requires an external zero-sequence CT. Executes in definite-time mode.

Phase Loss Protection

Activates when the maximum current unbalance exceeds 80% after motor start.

Current Unbalance Protection

Activates when the maximum current unbalance exceeds the set value and average current is above 25%.

Reverse Phase Sequence Protection

Activates 200ms after detecting incorrect three-phase current sequence.

Underload Protection

Detects abnormal low-load conditions such as pump cavitation, fan airflow loss, or conveyor belt breakage. Executes in definite-time mode based on current or power.