DOLD current relays for overcurrent and undercurrent monitoring

Current relays are electronic measuring relays that monitor AC or DC current and react when it rises above or drops below a set threshold. Depending on the version, a single device can supervise one load or several. They pack a wide range of monitoring functions into a compact housing. Typical uses include stone and woodworking machinery, and any application where over- or undercurrent has to be detected.

Simple single-phase relays that need no auxiliary supply include AI 837 (undercurrent) and AI 838 (overcurrent) for 0.5 to 16 A, and the 22.5 mm ML 9701 for 0.5 to 12 A. The 9270 (overcurrent) and 9271 (undercurrent) families cover AC 0.1 ... 100 A in IK, SK, IL and IP versions; IK and SK are 17.5 mm, IL is 35 mm, and the IP types are three-phase. IL 9277 and IP 9277 detect both over- and undercurrent, and IP 9278 checks current asymmetry.

For AC and DC measurement, BA 9053 covers 2 mA to 25 A with input frequencies up to 5 kHz and galvanic separation, MK 9053N offers 2 mA up to 10 A at 22.5 mm, and RL 9853 detects either over- or undercurrent on AC and DC networks. MK 9063N and MH 9063 add an LCD for measured values, and MH 9353 is a transducer with isolated analogue outputs (0 … 20 mA with 0 … 10 V, or 4 … 20 mA with 2 … 10 V).

• Monitors AC and DC currents
• Over- and undercurrent threshold detection
• AI 837 / AI 838 need no auxiliary supply
• IP 9278 for current asymmetry in 3-phase systems
• MK 9063N with LCD measured-value display
• Used on stone and woodworking machines