Installation manual

IM 1029-2 Magnitude™ Frictionless Centrifugal Chillers – Model WMC 43
Control Wiring
The control circuit on the Daikin centrifugal packaged chiller is designed for 115-volts. Control power is
supplied from a factory-wired transformer located in the electrical box.
VFD Line Harmonics
Despite their many benefits, care must be taken when applying VFDs due to the effect of line harmonics on the
building electric system. VFDs cause distortion of the AC line because they are nonlinear loads, that is, they
don't draw sinusoidal current from the line. They draw their current from only the peaks of the AC line, thereby
flattening the top of the voltage waveform. Some other nonlinear loads are electronic ballasts and
uninterruptible power supplies.
Line harmonics and their associated distortion can be critical to ac-drives for three reasons:
1. Current harmonics can cause additional heating to transformers, conductors, and switchgear.
2. Voltage harmonics upset the smooth voltage sinusoidal waveform.
3. High-frequency components of voltage distortion can interfere with signals transmitted on the AC
line for some control systems.
The harmonics of concern are the 5
th
, 7
th
, 11
th
, and 13
th
. Even harmonics, harmonics divisible by three, and high
magnitude harmonics are usually not a problem.
Current Harmonics
An increase in reactive impedance in front of the VFD helps reduce the harmonic currents. Reactive impedance
can be added in the following ways:
1. Mount the drive far from the source transformer.
2. Add line reactors. They are standard equipment on Magnitude chillers.
3. Use an isolation transformer.
4. Use a harmonic filter.
Voltage Harmonics
Voltage distortion is caused by the flow of harmonic currents through a source impedance. A reduction in
source impedance to the point of common coupling (PCC) will result in a reduction in voltage harmonics. This
can be done in the following ways:
1. Keep the PCC as far from the drives (close to the power source) as possible.
2. Increase the size (decrease the impedance) of the source transformer.
3. Increase the capacity (decrease the impedance) of the busway or cables from the source to the PCC.
4. Make sure that added reactance is "downstream" (closer to the VFD than the source) from the PCC.
Line Reactors
Five-percent line reactors are standard equipment on Magnitude chillers and located in each compressors power
panel. They are employed to improve the power factor by reducing the effects of harmonics.
Harmonic Filter
The harmonic filter is an option for field mounting and wiring outside of the power panel. It works in
conjunction with the line reactor to further minimize harmonic distortion. IEEE 519-1991 Standard defines
acceptable limits.
See the Magnitude certified drawings for harmonic filter dimensions and wiring information.
EMI (Electro Magnetic Interference) and RFI (Radio Frequency Interference) Filter
This filter is a factory-installed option. The terms EMI and RFI are often used interchangeably. EMI is actually
any frequency of electrical noise, whereas RFI is a specific subset of electrical noise on the EMI spectrum.
There are two types of EMI. Conducted EMI is unwanted high frequencies that ride on the AC wave form.