Winding resistance meter

Data records

• A winding resistance meter injects enough direct current to drive the transformer core toward saturation, which reduces the effective inductance of the winding and lets the current stabilize sooner; too low a current gives noisy, inconsistent readings and too high a current heats the winding, so the current is kept in a band expressed as a fraction of the rated winding current. Source: Megger application page, web page edition. Verified 2026-10-27. Record instr.winding-resistance-meter.core-saturation
• A winding resistance meter is a direct-current ohmmeter built for inductive test objects: it drives a regulated current through a transformer or rotating machine winding, waits for the current to stabilize, computes the resistance from the measured voltage drop, and then discharges the stored energy of the winding safely. Source: Electrical Testing Reference editorial taxonomy, 2026-10 edition. Verified 2026-10-27. Record instr.winding-resistance-meter.definition
• A direct-current resistance test leaves residual magnetism in the transformer core, and residual flux can cause high inrush current at energization and distort later exciting-current and frequency response measurements, so winding resistance meters include a controlled demagnetization function that is run after testing. Source: OMICRON application page, web page edition. Verified 2026-10-27. Record instr.winding-resistance-meter.demagnetization
• After a measurement the energy stored in the winding is dissipated through the instrument's discharge circuit, and a visible and audible discharge indicator shows while that is in progress; a panel-mounted emergency stop switch may also be fitted. Source: Raytech product page, web page edition. Verified 2026-10-27. Record instr.winding-resistance-meter.discharge-indication
• When a direct voltage is applied to a highly inductive winding the current rises quickly at first and then approaches its final value slowly, so the resistance can be read only after the current has settled; a high test current capability and dual-channel measurement of two windings at once are two ways in which a transformer ohmmeter shortens the test. Source: Megger Electrical Tester article, November 2015 edition. Verified 2026-10-27. Record instr.winding-resistance-meter.inductive-charging
• The meter reports the direct-current resistance of each winding or tap position; after temperature is taken into account, a change from baseline or earlier values indicates shorted turns, broken strands, or faulty or corroded connections between a winding and its bushing or inside a tap changer. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.winding-resistance-meter.result-interpretation
• When winding resistance is measured by winding on a transformer with an on-load tap changer, the test current is kept flowing while the tap changer is stepped through its positions, so every tap is measured from one connection, the core stays saturated after the first reading, and an interruption of the current during a tap change reveals a tap changer that fails to make before it breaks. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.winding-resistance-meter.tap-changer-stepping
• Winding resistance meters carry temperature inputs and correct the measured resistance to a reference temperature automatically, because the resistance of a copper or aluminum winding varies with temperature and results are compared across tests made at different temperatures. Source: Raytech product page, web page edition. Verified 2026-10-27. Record instr.winding-resistance-meter.temperature-correction
• Three-phase winding resistance test sets connect to all the transformer bushings at once and measure the three phases without switching cables, resolving the individual winding resistances inside a delta connection or a wye connection without an accessible neutral, and can also serve as micro-ohmmeters for circuit breaker contact resistance. Source: Doble (Vanguard Instruments) product page, web page edition. Verified 2026-10-27. Record instr.winding-resistance-meter.three-phase-sets