The Model 77C-KW/HP has important advantages over current monitors in many protection applications. Any motor load that has a small or very non-linear change in current vs. load requires the use of a power monitor for underload, dry run and dead-head protection. The change in power vs. load is more linear for most motor loads and is greater in magnitude than the change in current in all motor loads. This is because power measurements take into account both power factor (pf) and current. Small motors, those under 3 hp and especially fractional horsepower, exhibit small changes in current vs. load, but the change in power is large. When larger motors are derated (run below their rated horsepower) the change in current is small vs. load, but again, the change in power is large and linear. Other typical applications include slower speed mixer or agitator motors up to 50 hp and beyond. These motors and others that run slower than around 3400 rpm usually have small current changes vs. load. The built-in UL Listed/CSA approved overload, current unbalance, reverse phase, single-phase and other protection features are significant benefits over similar products. The Modbus communications capability allows this device to be directly integrated with the SymCom RM-1000 and RM-2000 remote displays or other remote monitoring and control equipment.
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