Danfoss VLT AutomationDrive FC 301, Руководство по конструкции, Страница: 20 / 200

NOTICE
EMC INTERFERENCE
Use screened cables for motor and control wiring, and
separate cables for input power, motor wiring and
control wiring. Failure to isolate power, motor and
control cables can result in unintended behaviour or
reduced performance. Minimum 200 mm (7.9 in)
clearance between power, motor and control cables is
required.
3.6 Controls
3.6.1 Control Principle
A frequency converter rectifies AC voltage from mains into
DC voltage, after which this DC voltage is converted into a
AC current with a variable amplitude and frequency.
The motor is supplied with variable voltage/current and
frequency, which enables variable speed control of 3-
phased, standard asynchronous motors and permanent
magnet motors.
The frequency converter is capable of controlling either
the speed or the torque on the motor shaft. Setting
1-00 Configuration Mode determines the type of control.
Speed control
There are 2 types of speed control:
•
Speed open loop control which does not require
any feedback from motor (sensorless).
•
Speed closed loop PID control requires a speed
feedback to an input. A properly optimised speed
closed loop control has higher accuracy than a
speed open loop control.
Selects which input to use as speed PID feedback in
7-00 Speed PID Feedback Source .
Torque control
The torque control function is used in applications where
the torque on motor output shaft is controlling the
application as tension control. Torque control can be
selected in
1-00 Configuration Mode , either in VVC
+
[4]
Torque open loop or Flux control closed loop with [2] motor
speed feedback . Torque setting is done by setting an
analog, digital or bus controlled reference. The max speed
limit factor is set in
4-21 Speed Limit Factor Source . When
running torque control, it is recommended to make a full
AMA procedure as the correct motor data are of high
importance for optimal performance.
•
Closed loop in Flux mode with encoder feedback
offers superior performance in all 4 quadrants
and at all motor speeds.
•
Open loop in VVC + mode. The function is used in
mechanical robust applications, but the accuracy
is limited. Open loop torque function works
basically only in one speed direction. The torque
is calculated on basic of current measurement
internal in the frequency converter.
Speed/torque reference
The reference to these controls can either be a single
refrence or be the sum of various references including
relatively scaled references. The handling of references is
explained in detail in
chapter 3.7 Reference Handling .
Basic Operating Principles
VLT
®
AutomationDrive FC 301/FC 302 Design Guide, 0.25-75 kW
18 MG33BF02 - Rev. 2013-12-20
3 3