The need to replace their four roof mounted condensers at the Dierbergs West Oak store prompted their initial search for alternate controllers. The store uses two 8-fan condensers, a 6-fan condenser and a 4-fan condenser to feed liquid refrigerant to their four racks. Using the KE2 Fan Control, which incorporates variable frequency drive
technology to vary the fan speed according to demand, benefited the company in several ways. First, through energy reduction, but additionally, by eliminating the stop and start surges typical with standard step control, there is less wear and tear on motor windings and bearings.
VFD keypad, operator control panel required for control, monitoring and measurements shall be supplied and installed outside the panel on the front door. It shall be accessible for operation without opening the front door and shall be non-removable type.
This phenomenon exists for all VFDs. However, VFDs < 2 hp are more susceptible to overload and overcurrent trips due the additional charging currents. This phenomenon is exhibited to a greater degree on 460 V VFDs than on 230 V VFDs due to the higher output transition voltage. This phenomenon is made worse by having long leads on small hp VFDs or multiple cable loads from a single phase VFD
. The rms current value of this charging current is made higher and may approach the VFD rms overload limit by increasing the carrier frequency (the number of device switchings per second). Shielded motor cable has higher capacitance line to line and line to ground than wires in a conduit and may increase the charging current magnitude. Capacitively coupled currents can also exist between the output wires of different VFDs that are routed in the same conduit. It is recommended that no more than 3 VFD output wires be routed in the same conduit to prevent additional VFD to VFD capacitive currents resulting from tightly bundled output wires in a conduit.
Registration date: Dec 18, 2013