Variable Frequency Drives
Contact: Igor Port phone +380933080489
Website: www.vfds.org email info@vfds.org
Address: Kharkov, Shen zhen, Guang dong China, 6
In Category: Energy > Energy Agents & Projects > Energy Projects
Main Products: variable frequency drive, AC drive
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Overload protection is designed to disconnect the individual motor from the variable frequency drive if the motor draws current greater than normal but less then eight times its FLA for a prolonged period of time. This protects the motor and the motor conductors from excessive heating. The most common types of motor overload protection technologies are bimetal and solid state.


Closed loop vector control variable frequency drive shall be used with features as specified:
a. Speed control 0.01%, dynamic 0.2%/sec, torque linearity <2%, torque rise time ~2 ms.
b. Starting Torque: 150 %, Frequency stability: +0.1%.
c. Overload: 110% load for 60 seconds. Once in every 10 minutes.
d. The ratio of peak inverse voltage to peak voltage of the VFD shall be more than 2.5 (under normal operating conditions).
e. VFD Design temperature: 45 ÂșC.
f. Speed range: 1 % to 270% of the normal speed of the motor.

Diverting Noise from Susceptible Equipment with Proper Cabinet Layout: Grouping the input and output conduit/armor to one side of the cabinet and separating the Programmable Logic Controller (PLC) and susceptible equipment to the opposite side will eliminate many effects of CM noise currents on PLC operation. CM noise current returning on the output conduit or armor will flow into the cabinet bond and most likely exit out the adjacent input conduit/armor bond near the cabinet top, well away from sensitive equipment. CM current on the return ground wire from the motor will flow to the copper PE bus and back up the input PE ground wire, also away from sensitive equipment. If cabinet PE ground wire to the closest building structure steel is deemed necessary, then if this wire is taken from the right side under the conduits and single phase VFD, the CM noise is still shunted away from the PLC backplane.


With this three-contactor bypass arrangement, the motors can still run if the variable frequency drive were to fail, although only at rated speed rather than at a speed controlled by the variable frequency drive. The contactors upstream and downstream of the variable frequency drive are opened, and the bypass contactor D is closed. This bypasses the variable frequency drive and connects all of the motors directly to line power. This arrangement is very common in HVAC applications.