and stops.
(3) Speed governor: Variable speed governor for speed limiting
and pneumatic operator to maintain an adjustable preset level in
[deaerator tank] [condensate receiver] by variation of turbine
speed. Input to the operator shall be a 20 to 103 kPa (gage) 3 to
15 psig pneumatic signal and vary the turbine speed from minimum
to full speed in a linear response.
Maximum and minimum speed
shall be adjustable. Provide an electro-pneumatic transducer to
accept the 4 to 20 mA signal from the controller specified in VAMS
speed governor and shall operate a separate trip valve.
(5) Insulation: Turbine shall insulated and lagged as specified
in Section 15080 THERMAL INSULATION FOR MECHANICAL SYSTEMS.
2.14.5
Variable Speed Control for Motors
Remotely installed cabinet housed units with solid state rectification and
inverter equipment to vary frequency of electrical power to drive motors.
2.14.5.1
Housing
a.
House controller in a [wall] [floor] mounted, NEMA 250 enclosure
finished with manufacturers standard painted finish.
Provide
control panel complete with fused disconnect switches, magnetic
[across the line] [part winding] starters with thermal overload
protection, transformer, hand-off-automatic selector switches,
hand potentiometer for manual speed control, fuses and running
lights.
b.
Provide manual switch within control panel so that in the event of
failure of a component, the motor can be put across the line at
full voltage to maintain air or pump pressure. Provide a
mechanical door interlock that will allow the panel to open only
when the fused disconnect is in the off position.
2.14.5.2
Variable Frequency Controllers
Variable frequency controllers shall use solid-state semiconductor power
conversion equipment. Provide controllers as integrated and assembled
products. Provide controllers by the same manufacturer.
a.
Each controller shall be rated for a supply of [_____] volts,
three phase, 60 Hz. The output shall be [_____] volts, three
phase with frequency variable between zero and 60 Hz. Controllers
shall be rated to operate the motors continuously at their rated
horsepower and frequency. Speed regulation shall be three percent
or better without tachometer feedback. The electrical supply
system has an available short circuit rating of [_____] amperes
symmetrical.
b.
Each controller shall be capable of driving the motor continuously
at a lower speed no greater than 20 percent of full rated motor
speed with stable operation and without overheating the motor
under rated ambient conditions. Provide estimate of minimum speed
at which motor can be operated continuously without overheating or
SECTION 15502N
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