Load monitoring relays for current, cos phi and active power

DOLD measuring relays for load monitoring supervise electrical loads by measuring current, cos φ or active power. The range covers current relays, load converters and monitors for underload, normal load and overload. Typical uses are motor monitoring and checking that electrical consumers are working as intended, both of which support higher productivity.

For underload detection by cos phi, the IK 9065 and SK 9065 (17.5 mm) need no auxiliary supply and connect motors with up to 5 A rated current directly, while the SL 9065CT has a built-in current transformer that extends the range to 100 A. The BA 9065 suits AC and DC motors and 400 Hz systems, and can optionally be used with motors on frequency converters.

Where active power is the better indicator, the MK 9397N (22.5 mm, 1 changeover contact) and MH 9397 (45 mm, separate contacts for overload and prewarning) act as motor load monitors. The BH 9097 sets two thresholds, P1 and P2, with adjustable start-up and switching delays. The BH 9098 transmitter handles up to 40 A without an external CT, the MH 9398 provides galvanically isolated analog outputs, and the BH 9140 and RP 9140 respond to 2 to 20 % reverse power.

• Monitors current, cos φ and active power
• IK 9065: cos phi underload, no auxiliary supply
• SL 9065CT with built-in CT up to 100 A
• MH 9397 for overload plus prewarning
• BH 9140 / RP 9140 for reverse power