Specifications - City of Montpelier, Vermont

Title:Montpelier District HeatingCity of Montpelier, VT16480 – MOTOR CONTROLLERSIssue Date:September 28, 2012Page #:7 of 12l. The overload rating of the drive shall be 110% of its variabletorque current rating for 1 minute every 10 minutes, and 140% ofits torque current rating for 2 seconds every 15 seconds.m. The VFD shall have input line fuses standard in the driveenclosure.n. The VFD shall have a DC Link Choke or three percent line reactorto reduce the harmonics to the power line and to increase thefundamental power factor.o. The VFD shall be optimized for the carrier frequency to reducemotor noise and provide high system efficiency. The carrierfrequency shall be adjustable by the startup engineer.9. All VFD’s will have following adjustments:a. Two (2) programmable critical frequency lockout ranges to preventthe VFD from continuously operating at an unstable speed.b. PI Set point controller shall be standard in the drive, allowing apressure or flow signal to be connected to the VFD, using themicroprocessor in the VFD for the closed loop control; thuseliminating the need for external controllers.c. Two (2) programmable analog inputs shall accept a current orvoltage signal for speed reference or for reference and actual(feedback) signals for PI controller. Analog inputs shall include afilter; programmable from 0.01 to 10 seconds to remove anyoscillation in the input signal. The minimum and maximum values(gain and offset) shall be adjustable within the range of 020 mAand 010 Volts. Additionally, the reference must be able to bescaled so that maximum reference can represent a frequency lessthan 60 Hz, without lowering the drive maximum frequency below60 Hz.d. Five (5) programmable digital inputs for maximum flexibility ininterfacing with external devices. One digital input is to be utilizedas a customer safety connection point for fire, freeze and smokeinterlocks (Enable). Upon remote, customer reset (reclosure ofinterlock), drive is to resume normal operation.e. Two (2) programmable analog outputs proportional to Frequency,Motor Speed, Output Voltage, Output Current, Motor Torque,Motor Power (kW), DC Bus voltage, or Active Reference.f. Two (2) programmable digital relay outputs. The relays shall berated for maximum switching current 8 amps at 24 VDC and 0.4amps at 250 VAC; Maximum voltage 300 VDC and 250 VAC;MOTOR CONTROLLERS 16480 7