Power-Up-Circuit Power Start Control Assembly Unit

Module Feature

Power-Up-Circuit is a custom functional circuit assembly for controlled power-on sequence of high-power electrical equipment.

It is widely applied in VFD, DC power supply, UPS and servo drive cabinets to limit inrush current when energizing DC bus capacitors. The assembly contains precharge resistors, precharge contactor, main contactor, timing logic, interlock DI/DO and fault feedback loop. It executes two-stage power-up: first low-current precharge, then switch to main contact after bus voltage reaches threshold. It has overcurrent, over-temperature and interlock protection, can be matched with PLC or relay logic. Widely stocked as spare for industrial MCC, test bench and power conversion cabinet.

Working principle

When enable signal is received, the precharge contactor closes first. DC bus capacitor charges slowly through precharge resistor to suppress huge inrush surge. After delay or voltage feedback confirms precharge complete, main contactor pulls in to bypass the resistor and supply full power to power stage. If precharge timeout, overcurrent or hardware fault is detected, the circuit locks startup and outputs fault alarm.

Onboard components

Precharge power resistor, precharge contactor, main contactor, voltage sampling circuit, timing / logic control unit, fuse, thermal protection switch, terminal block and wiring harness.

LED indicators

Status LEDs for Precharging, Ready, Fault and Main Contactor Closed.

Hardware self‑diagnosis

Monitors bus voltage rise rate, precharge timeout, resistor over-temperature and contactor feedback contact abnormality. Logic configuration is completed by PLC programming software or relay logic drawing.

Programming softwarePLC programming tool (if logic is PLC based), used for startup time setting, interlock condition and fault alarm logic editing.

Electrical & Process Parameters

Model:POWER-UP-CIRCUIT Brand:Custom / General industrial assembly Device type:Precharge power-up control circuit assembly Function:Inrush current limiting and sequenced startup for power electronic equipment

Mechanical & Structure

Mounting:Cabinet DIN rail or chassis mounting Protection class:IP20 Housing:Open frame or enclosed plastic housing

Environmental

Operating temperature:-5℃ ~ +50℃ Storage temperature:-40℃ ~ +85℃ Ambient humidity:5~95% non‑condensing

Certification:CE, IEC61800 related Status:Original industrial power control spare

Installation

Isolate high voltage power and confirm capacitor discharge before replacement. Match bus voltage rating, check contactor and resistor rating, verify feedback wiring, test precharge timing and fault interlock function after commissioning.

Interface

Main power input terminals, precharge loop terminals, enable DI, ready / fault DO feedback terminals.

Diagnostic

Precharge timeout: Resistor open circuit, capacitor leakage, contactor not pull in. Large inrush trip: Precharge circuit failed, main contact closed too early. Contactor chatter: Control voltage unstable, coil damage.

Product BriefPOWER-UP-CIRCUIT assembly, industrial precharge power-up control spare for drive and power conversion cabinet replacement.