Understanding Relay Contact Voltage Drop and Its Effects > 자유게시판

When electrical current flows through a relay contact, a small voltage drop occurs across the contact surfaces

Even a few millivolts of loss may trigger malfunctions in sensitive electronic environments

This phenomenon arises due to the unavoidable resistive properties of contact alloys

When current passes through this resistance, energy is lost as heat, resulting in a voltage difference between the input and output sides of the contact

This voltage drop becomes more noticeable under high current loads

In applications like motor controllers or heating circuits, resistances as low as 50 milliohms can yield drops exceeding 300 mV

In precision analog systems—including 3.3V or 5V sensor networks—this loss can disrupt signal integrity

Even a 0.3V reduction below nominal can cause digital thresholds to be misread, leading to erratic behavior

Over time, repeated voltage losses contribute to progressive contact deterioration

Frequent arcing and current surges gradually wear down contact material and promote surface corrosion

Higher resistance elevates the potential difference, deepening the energy loss

This thermal runaway cycle exponentially worsens contact condition over time

Prolonged degradation may result in welded contacts that fail to open, or open-circuit conditions with no current flow

Temperature also plays a role

When external heat merges with resistive heating, thermal thresholds are easily exceeded

In sealed or cramped electrical cabinets, heat dissipation is severely limited

Thermal stress from combined sources can lead to unexpected, early-stage relay collapse

Choosing relays rated for higher current margins than the nominal load reduces stress and minimizes voltage loss

Silver-cadmium oxide or silver-nickel contacts offer superior conductivity and arc resistance

In environments demanding reliability, replacing electromechanical relays with solid-state alternatives prevents contact degradation

Proactive diagnostics—including contact resistance testing—identify degradation trends early

Monitoring the actual voltage at the load side during operation can reveal if a voltage drop is occurring beyond acceptable limits

Proactively managing voltage drop ensures stable performance, minimizes downtime, and protects sensitive equipment