MWA300 and MWA330A three-phase ratio and winding resistance analyzers

Overview

The Megger MWA300 and MWA330A are three-phase ratio and winding resistance analyzers that combine transformer turns ratio (TTR) and DC winding resistance testing in a single unit. They provide complete ratio, phase, and winding resistance measurements with only one three-phase lead set connection and perform DC resistance measurements on all high- and low-side windings without reconnection. The instrument has an eight-terminal/six-winding resistance measurement capability and does not require any interconnected boxes. The MWA family includes a built-in automatic core demagnetisation function and is described as 55 % smaller and 40 % lighter than individual units to improve portability and reduce set-up time. The MWA300 is externally controlled by PowerDB software running on an external PC; the MWA330A includes a built-in computer with a 305 mm (12 in) color touch screen and can store up to 100 000 data sets. Technical specifications: Automation Yes; Max output current (DC) 10 A; Single-phase/3-phase capability 3-phase. The MWA300 and MWA330A can be used to test power transformers, distribution transformers, CTs and VTs, and motors and generators. With a single three-phase lead set connection the instruments can perform the following tests and functions: - Three-phase turns ratio - Three-phase winding resistance - OLTC continuity (make-before-break) - Three-phase core demagnetization - Magnetic balance/flux distribution - Excitation current - Polarity and phase angle deviation - Auto vector detection - Heat-run test When performing winding resistance tests on a transformer equipped with a load tap changer (LTC), the instrument can continue injecting DC current while switching through the taps to verify the LTC’s make-before-break functionality.