Megger Multi-Amp Relay Test Unit

Module Feature

Multi-Amp is a historic US brand founded in 1951, now integrated into Megger portfolio, specialized in protective relay and low voltage circuit breaker test equipment.

These test sets adopt variable high-current transformer structure, providing adjustable AC injection current for overload relay, thermal relay and electromagnetic protection device testing. Many classic models support continuous high-current output, built-in timer and analog ammeter display, rugged portable metal enclosure for outdoor substation field service. It is widely deployed for commissioning and periodic maintenance of protection relays in power plants, distribution substations and industrial MCC rooms.

Working principle

Mains input power feeds into internal variable autotransformer and step-down high-current transformer.

The unit outputs large adjustable low-voltage test current to the secondary side of current transformers or directly to relay heating elements. The built-in timer records relay trip time, verifying overload characteristic curve, pickup value and trip accuracy of protective devices.

Onboard components

Variable autotransformer, high-current output transformer, current metering circuit, trip timing module, output binding posts, power switch, portable hard shell carrying case, test lead assembly.

LED indicators

Not applicable for classic analog Multi-Amp units; digital variants include power and run/fault LED indicators.

Hardware self‑diagnosis

No built-in electronic self-diagnosis for traditional analog models. Routine maintenance checks include winding insulation resistance, contact condition, meter calibration and output current linearity.

Programming software

Dedicated Multi-Amp test software for digital versions, used for test template setup, characteristic curve recording and test report generation.

Electrical & Process Parameters

Model:MULTI-AMP Brand:Multi-Amp (Megger) Device type:Secondary injection protective relay test set Function:Current injection test, trip characteristic verification and calibration for overload relays and circuit breakers

Mechanical & Structure

Mounting:Portable handheld / bench placement Protection class:IP40 Housing:Shock-resistant molded metal portable case

Environmental

Operating temperature:-10℃ ~ +50℃ Storage temperature:-40℃ ~ +85℃ Ambient humidity:5~95% non‑condensing

Certification:CE, NIST traceable calibration supported

Status:Original Megger legacy electrical test instrument spare

Installation

Place the unit on stable ground and keep ventilation clear.

Connect input power and test output leads to relay under test, set target current value and start timing function before injection test.

Interface

AC power input terminal, high-current test output binding posts, trip signal input terminals.

Diagnostic

No current output: Input fuse blown, autotransformer winding open or power switch failure. Inaccurate current reading: Meter calibration drift, loose output terminal or contact resistance excess. Timer malfunction: Timing circuit fault or trip signal wiring open.

Product Brief

Megger Multi-Amp test set, portable secondary injection instrument for protective relay and circuit breaker calibration and maintenance in power substations.