Overview
The ARD-KHD-S03 series is a voltage sag mitigation terminal designed by Acrel specifically for low-voltage motor control circuits.
It addresses contactor dropout and unplanned VFD/soft-starter shutdowns caused by voltage sags from lightning, grid switching, or large motor starts.
The device offers dual-mode solutions: Ride-Through + Restart. Utilizing supercapacitor energy storage technology, it responds within milliseconds to maintain contactor closure during sags and perform batch restart upon voltage recovery — all independently without a host system.
Covering standard AC contactors, energy-saving contactors, VFD/soft-starter circuits, it is an essential component for industries requiring high power supply continuity such as petrochemical, semiconductor, and data centers.
Highlight
Supercapacitor Energy Storage
- Supercapacitor ride-through, 0.020~10.999s programmable hold time
Smart Restart
- Batch restart, anti-impact delay, VFD/soft-starter dedicated logic
Full-Scenario Selection
- Standard/energy-saving/VFD models, precise fit for any contactor type
Traceable O&M
- 6-type event log, Modbus RTU, optional IP65 remote display with USB upgrade
Focus Areas
| Industry | Application | ARD-KHD-S03 Value |
| Petrochemical | Continuous reactors, transfer pumps | Prevents interlock trips due to sags, avoids media solidification/process interruption |
| Semiconductor | Cleanroom AHU, cooling water | Millisecond ride-through, ensures stable temp/humidity |
| Data Center | Precision AC, cooling towers | Maintains fans/pumps during sags, prevents IT equipment overheating |
| Ports/Cranes | STS/RTG control circuits | Suitable for frequent ops, prevents contactor chattering |
| Metallurgy/Cement | Kiln ID fans, conveyors | Withstands grid fluctuations, reduces unplanned kiln stoppage losses |
| VFD/Soft-starter | Pumps, fans, compressors | Fault detection + auto reset, sag restart capability |
Specification
| Item | Parameter |
| Auxiliary Power | S03A/F/J: AC220V±20% S03B: AC380V±20% S03D: AC110V±20% |
| Contactor Rated Voltage | AC110V / AC220V / AC380V |
| Sag Hold Time | 0.020 ~ 10.999s (resolution 0.001s) |
| Restart Delay | 0.1 ~ 99.9s (batch start) |
| Max Restart Window | Sag hold time ~ 999.9s |
| Digital Input | 4 channels, dry contact, built-in DC24V |
| Relay Output | 4 channels, NO, AC250V/10A (resistive) |
| Communication | 1x Modbus RTU (RS485), optional |
| Event Log | Sag/DI-DO/contactor/device/power-on/swell-sag, 16 entries each (optional) |
| Main Display | Monochrome dot-matrix LCD, 98×60mm |
| Remote Display | IP65 (flush mounting), cutout 92×55mm, optional USB upgrade |
| Operating Temperature | -10℃ ～ +55℃ |
| Storage Temperature | -25℃ ～ +70℃ |
| Protection Rating | Main unit IP30, remote display IP65 |
| Mounting | 35mm DIN rail / panel flush (display unit) |
| Pollution Degree | 3 |
| Installation Category | III |
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Function
| Function | Description | S03A/B/D | S03F | S03J |
| Ride-Through | Supercapacitor holds contactor during voltage sag | √ | — | √ |
| Sag Restart | Delayed restart output after voltage recovery | √ | √ | √ |
| VFD Restart Logic | Detects close/run/fault status, auto-reset restart | — | √ | — |
| Closing Status Detection | DI (aux contact) or voltage detection | √ | √ | √ |
| 3-Phase Voltage Sensing | Bus voltage measurement for restart logic | — | √ | — |
| Energy-Saving Coil Drive | Direct coil holding voltage output | — | — | √ |
| Communication | 1x RS485, optional module C | Optional | Optional | Optional |
| Event Log | 6 event types, 16 entries each, optional SR module | Optional | Optional | Optional |
| Remote Display | IP65 flush-mount display, optional 60L | Optional | Optional | Optional |
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Model Selection
| Model | Applicable Circuit | Key Feature |
| ARD-KHD-S03A | AC220V standard AC contactor | Coil impedance ≤1000Ω |
| ARD-KHD-S03B | AC380V standard AC contactor | Coil impedance ≤1000Ω |
| ARD-KHD-S03D | AC110V standard AC contactor | Coil impedance ≤1000Ω |
| ARD-KHD-S03F | VFD / Soft-starter | 3-phase voltage sensing + DI fault/run detection, restart logic |
| ARD-KHD-S03J | Energy-saving contactor | Coil impedance MΩ, direct coil holding output |
If contactor impedance is unknown or ≥400A → MUST use S03J + DI closing status detection
VFD/Soft-starter circuits → S03F ONLY (Do NOT use S03A/B/D/J)
Summary
The ARD-KHD-S03 is Acrel’s specialized voltage sag mitigation terminal for industrial low-voltage continuous production scenarios. It is more than an anti-sag module — it is an intelligent contactor companion integrating energy storage ride-through, logic restart, status detection, and event traceability. With precise model segmentation and flexible DI/DO programming, the S03 series seamlessly embeds into any motor circuit — standard contactors, energy-saving contactors, VFDs, or soft-starters. For modern factories pursuing power continuity, equipment high availability, and O&M traceability, ARD-KHD-S03 is the standardized, low-cost, easy-to-deploy ideal solution.
FAQ
DI1 (Close), DI2 (Fault), and DI3 (Run) must be wired. Wiring only the Close signal will disable the fault reset logic. DI4 is optional for sag block.
It is recommended to use DI detection mode: connect the contactor NO auxiliary contact to DI and set “Closing Status Detection” to “DI”. Mandatory for contactors ≥400A.
The supercapacitor floats continuously when powered. In high-temperature environments, periodically read capacitor voltage via comm. (0x0D). If <10V, please return for maintenance.
10.999 seconds. Resolution 0.001s, fine-tunable to match different contactor dropout characteristics.
Yes. Only available with optional 60L remote display unit. Insert USB drive, enter “USB Function” menu to upgrade device firmware.
Set DO to “Restart Output” (Low byte=2), parallel connect with the Start button. After voltage recovery and batch delay, the DO closes — equivalent to pressing the Start button.
S03J is for energy-saving contactors (coil impedance MΩ), directly outputs coil holding voltage. S03A is for standard contactors (impedance ≤1000Ω), series-connected in the control circuit. Not interchangeable.
Standard cable length is 1.5m (Ethernet cable), with optional 3m and 5m lengths. For reliable communication, the maximum recommended length is 5m.
Two methods: 1) Via display menu “System parameters” → “Factory reset”, select “Yes”; 2) Write 0xFFFF to communication address 0x2B (43).
Yes. With optional Ethernet (MODBUS TCP) or 4G gateway, it can connect to third-party IoT platforms via MQTT protocol. We provide open Modbus register maps and API documentation.
