Rockwell Automation 1336T FORCE Series B - Manual (Page 278)

Appendix A
A–30
Sensorless Application Notes Sensorless vs. Encoder Application Guidelines–
– Sensorless is applicable when Speed Regulation requirements are
greater than +/– 1.0% of base speed. Sensorless may be applicable
for regulation requirements between 0.2% and 1.0% with manual
adjustments. Encoder operation is recommended below 0.2%.
– Sensorless is applicable when the minimum speed is greater than 1/40
of base speed (i.e. 45 RPM on a 60 Hz, 4 pole motor). Sensorless
may be applicable down to speeds of 1/60 of base speed (30 RPM) if
high bandwidth responses are not required. Encoder operation is
recommended for speeds < 1/60 of base speed (30 RPM).
– Maximum Speed is the same for sensorless and encoder operation.
– The maximum velocity bandwidth achievable with sensorless is
approximately twice the default bandwidth value.
Bandwidths higher than this may require an encoder because the
velocity ripple may be intolerable or there may be stability problems.
The maximum bandwidth achievable with sensorless is half the
bandwidth achievable with an encoder. Note that the maximum
achievable bandwidths decrease with increasing inertia for both
sensorless and encoder.
– The starting torque available is the same with sensorless or encoder.
Available starting torque is at least 150% motor torque and could be
as high as 200% if the inverter can supply the current.
– Minimum (current limit) acceleration and deceleration times are
comparable with sensorless and encoder.
– Torque regulation (+/–5%) is comparable with sensorless and encoder
at velocities greater than approximately 25% of base speed. At lower
speeds sensorless torque regulation may degrade with changing motor
temperature.
– Torque response is comparable with sensorless and encoder (400Hz).
Sensorless Mode Selection –
– Param 150 = 5
Minimum preset speed is 1/60 of base speed. When preset speed
and actual speed are both <1/60 of base speed, torque is set to zero.
When preset speed is > 1/60 of base speed, torque will be developed
to accelerate the motor through the min. speed to the preset speed.
When a motor is accelerated from a preset speed of 0 to a preset
speed > 1/60 of base speed, the motor will accelerate at the accel rate
set by the drive. But, if the accel rate in the drive is set to 0 or some
low value and the acceleration is controlled by ramping the preset
speed parameter with a PLC, the motor will not accelerate until the
preset speed is > 1/60 base speed. This will result in an accel delay
until that speed is reached, followed by an acceleration at the speed
set by the PLC. If this is a problem, Mode 7 should be used.
– Param 150 = 6
Minimum preset speed is 1/1000 of base speed. Preset speeds down
to zero are permitted, although it is very likely that the motor will not
operate smoothly at these low speeds. This mode will eliminate the
problems associated with controlling the acceleration rate by ramping
preset speeds from a PLC described in Mode 5 (Param 150 = 5).
– Param 150 = 7 (Available in 3.01 version)
Minimum present speed is 1/1000 of base speed. This mode is
similar to mode 6 except that the motor can be expected to operate
more smoothly and develop higher continuous torque at speeds < 1/60
of base speed. This mode will also allow operation with lower