a. The VFD shall be refrigerant cooled, microprocessor based, pulse width modulated design. Water cooled designs are not acceptable.
b. Input and output power devices shall be Insulated Gate Bipolar Transistors (IGBTs).
c. Active rectifier shall convert incoming fixed voltage/frequency to fixed DC voltage. Input current and voltage shall be regulated.
d. Transistorized inverter and control regulator shall convert fixed DC voltage to a sinusoidal PWM waveform.
e. Low voltage control sections and main power sections shall be physically isolated.
f. Integrated controls shall coordinate motor speed to optimize chiller performance over a wide variety of operating conditions.
a. Pre-painted unit mounted, NEMA 1 cabinet shall include hinged, lockable doors and removable lifting lugs.
b. The VFD shall have a short circuit interrupt and withstand rating of at least 65,000 amps.
c. Provisions to padlock main disconnect handle in the “Off” positions shall be provided. Mechanical interlock to prevent opening cabinet door with disconnect in the “On” position or moving disconnect to the “On” position while the door is open shall be provided.
d. Provisions shall be made for top entry of incoming line power cables.
3. Heat Sink:
a. The heat sink shall be refrigerant cooled. Heat sink and mating flanges shall be suitable for ASME design working pressure of 185 psig (1276 kPa).
b. Refrigerant cooling shall be metered by microprocessor-controlled solenoid valve to maintain heat sink temperature within acceptable limits for ambient temperature.
4. VFD Rating:
a. Drive shall be suitable for operation at nameplate voltage ±10%.
b. Drive shall be suitable for continuous operation at 100% of nameplate amps and 150% of nameplate amps for 5 seconds.
c. Drive shall comply with applicable ANSI, NEMA, UL and NEC standards.
d. Drive shall be suitable for operation in ambient temperatures between 40 and 122 F (4 and 50 C), 95% humidity (non-condensing) for altitudes up to 6000 ft (1829 m) above sea level. Specific drive performance at jobsite ambient temperature and elevation shall be provided by the manufacturer in the bid.
5. User Interface:
A single display shall provide interface for programming and display of VFD and chiller parameters. Viewable parameters include:
a. Operating, configuration and fault messages
b. Frequency in hertz
c. Load and line side voltage and current (at the VFD)
e. IGBT temperature
6. VFD Performance:
a. The VFD Voltage Total Harmonic Distortion (THD) and Harmonic Current Total Demand Distortion (TDD) shall not exceed IEEE-519 requirements using the VFD circuit breaker input terminals as the point of common coupling (PCC).
b. The VFD full load efficiency shall meet or exceed 97% at 100% VFD rated ampacity.
c. Active rectifier shall regulate unity displacement power factor to 0.99 or higher.
d. Voltage boost capability to provide full motor voltage at reduced line voltage conditions.