to Rockwell Automation, drives such as the Allen-Bradley PowerFlex
4 can benefit commercial washing machines by providing variable
speed throughout washing, rinsing, and high-speed spinning
cycles. In laundromats, where customers tend to overfill the
washing drums, the drive maintains consistent motor speed to
help eliminate tripping due to overload conditions. This can
save wear and tear on the motor and, ultimately, improve end-user
Available in power ratings from 0.2-3.7 kW (0.25-5 hp) and in voltage
classes of 115, 230, and 480 V, the Allen-Bradley PowerFlex 4ª has
reportedly been designed to meet OEM demands for flexibility, space savings,
and ease of use for speed control of many appliance applications.
"The Allen-Bradley PowerFlex 4 variable speed a.c. drive benefits numerous
appliance applications, especially appliances with fans or compressors,
such as residential and commercial HVAC equipment," Stan Ho, Allen-Bradley
drives product line manager, tells APPLIANCE. "Drives provide soft
starting - as opposed to the typical motor starting procedure of applying
full power with a simple off/on switch. The soft starting decreases energy
consumption and stress on the motor," he adds.
Mr. Ho says drives
such as the PowerFlex 4 can also offer flexibility. "Drives
also add flexibility for higher appliance performance. For example, designers
of commercial floor-care appliances can apply variable speed drives to
provide both low-speed for scrubbing and high-speed for waxing," he
explains. "Many drives can provide good torque at high speeds, but
the real challenge is providing good torque at low speeds. In the case
of a floor buffer, poor low-speed torque might result in improperly applied
wax. The PowerFlex 4 and its sensorless vector performance help appliances
maintain even, consistent operation at low speeds for improved performance."
drive's three different voltage options also makes it compatible with
commercial and residential voltage ratings. "Most drives on
the market feature only 230- and 480-V models, requiring designers to
provide a transformer
or a secondary power source in machines to step the 120 V up to 230 V.
That takes up space and adds weight," Mr. Ho explains. "Rockwell
Automation engineers designed the PowerFlex 4 with a 120-V input and
- within the drive - steps it up to three-phase, 230-V output. This saves
the cost, weight, and space of a transformer."
The drive's preset
speeds can be especially beneficial to appliance OEMs with varied product
lines, says Mr. Ho. "Designers can take advantage
of this feature if they're making appliances with multiple models," he
explains. "[For example], an economy model that might feature a
push button with low and high speed, and a deluxe model that might have
low speeds and two high speeds."
Available in 152 (H) x 80 (W) x 136
mm (D) (5.90 x 3.15 x 5.35 in), the PowerFlex 4 features Zero Stackingª,
which allows the drive to be mounted side by side, saving panel space.
It also has a relay-driven output
with a normally open and normally closed contact, which means engineers
can use the output to send a signal that illuminates the fault indicator
on applications such as a washing machine or buffer, according to Mr. Ho. "In
a sense, the output gives end users a window into the motor status," he