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Sensorless vector – Rockwell Automation 20A PowerFlex 70EC/700VC User Manual

Page 56

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52

Motor Control Modes

2. Custom

Custom Volts/Hertz allows a wide variety of patterns. The default configuration
is a straight line from zero to rated voltage and frequency. As seen in the
diagram below, the volts/hertz ratio can be changed to provide increased torque
performance when required by programming 5 distinct points on the curve:

Start Boost - Used to create additional torque for breakaway from zero

speed and acceleration of heavy loads at lower speeds

Run Boost - Used to create additional running torque at low speeds. The

value is typically less than the required acceleration torque. The drive will
lower the boost voltage to this level when running at low speeds (not
accelerating). This reduces excess motor heating that could be caused if the
higher start / accel boost level were used.

Break Voltage/Frequency - Used to increase the slope of the lower portion

of the Volts / hertz curve, providing additional torque.

Motor Nameplate Voltage/Frequency - sets the upper portion of the curve

to match the motor design. Marks the beginning of the constant power region

Maximum Voltage/Frequency - Slopes the portion of the curve used above

base speed.

Sensorless Vector

Sensorless Vector mode uses a V/Hz core enhanced by excellent current resolution,
a slip estimator, a high performance current limiter and the vector algorithms.

The algorithms operate on the knowledge that motor current is the vector sum of
the torque and flux producing components. Values can be entered to identify the
motor values or an autotune routine can be run to identify the motor values (see
"Autotune" on

page 16

). Sensorless vector offers better torque production and a

wider speed range than V/Hz. However, it may not be appropriate when more than
one motor is connected to the same drive.

Maximum Voltage

Maximum
Frequency

Base Voltage

(Nameplate) Voltage

Base Frequency

(Nameplate)

Break

Frequency

Run Boost

Start/Accel Boost

Break Voltage

Vector

Control

Slip

Estimator

V/Hz Control

CURRENT FEEDBACK - TOTAL

CURRENT FEEDBACK

TORQUE I EST.

T

ORQ

UE I EST

.

TORQUE I EST.

V VECTOR

SPEED REF.

FREQUENCY REF.

SLIP FREQUENCY

ELEC. FREQ.

V REF.

GATE

SIGNALS

Current

Resolver

+

+

Current

Limit

V/Hz

Voltage
Control

Inverter

Motor

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