3 Internal Adjustable Frequency Drive Operation
3.1 General
This section is intended to provide an operational overview of the adjustable frequency drive’s
main assemblies and circuitry. With this information, a repair technician should have a better
understanding of the adjustable frequency drive's operation and aid in the troubleshooting proc-
ess.
3.2 Description of Operation
An adjustable frequency drive is an electronic controller that supplies a regulated amount of AC
power to a three-phase induction motor in order to control the speed of the motor. By supplying
variable frequency and voltage to the motor, the adjustable frequency drive controls the motor
speed, or maintains a constant speed as the load on the motor changes. The adjustable frequency
drive can also stop and start a motor without the mechanical stress associated with a line start.
In its basic form, the adjustable frequency drive can be divided into four main sections: rectifier,
intermediate circuit, inverter, and control (see Figure 3-1).
Figure 3.1: Control Card Logic
To provide an overview, the main adjustable frequency drive components will be grouped into
three categories consisting of the control logic section, logic to power interface, and power section.
In the sequence of operation description, these three sections will be covered in greater detail
while describing how power and control signals move throughout the adjustable frequency drive.
High Power Service Manual for VLT
®
FC Series
Adjustable Frequency Drives
3 Internal Adjustable Frequency Drive Opera-
tion
MG.90.L1.22 - VLT
®
is a registered Danfoss trademark
3-1
3
Содержание VLT HVAC FC 100
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