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