According to Varidigm, its patented
VSM-CA3 controller can solve some of the issues related to dimmer-type
switches such as heat generation and noise.
The VSM-CA3 controller provides modulating control of a.c. induction
motors in response to an analog input signal from building automation
systems, thermostats, or other control devices. It provides continuous
motor speed in response to 0-10 V d.c. or 4-20 ma d.c. input signals.
patented controller receives the signal and responds by adjusting the
fan motor speed. The VSM-CA3 is said to be capable of modulating
the fan motor to a speed just one-fourth the rated maximum speed. This
turn-down ratio is said to be far greater than has historically been
feasible with a.c. motors controlled with either three-speed or dimmer-type
"Other people have been modulating commercial air-moving devices
like fan-powered VAV boxes, fan coil units, and ventilators for years
dimmer-switch type controllers," explains Mike Woolsey, commercial
sales manager for Varidigm. "But there's been a common thread of
complaint with the fact that the dimmer switches seem to shorten the
motor life, and they also don't have a high enough 'turn-down ratio,'
which is how far off the maximum you can slow down the motor. For example,
a 2-to-1 turndown ratio represents a 50-percent reduction in speed. Our
product is capable of a 3-to-1 ratio, which is probably its greatest
benefit, but it does it in a way that overcomes the issues with the dimmer-switch
type controller. That is, it doesn't generate as much heat and is quieter.
Another feature is that it doesn't cost as much a variable frequency
According to the company, with the VSM-CA3 controller, when
a fan motor slows down, energy savings occur. This, in turn, reduces
cost of the HVAC equipment in which the fan is installed. In addition,
the controller reportedly allows building owners to increase occupant
comfort by dramatically reducing the draft felt by occupants. The soft
start and soft transition between speeds also reduces the noise generated
by the fan.
The major design benefit of the controller is its heat reduction
compared to dimmer-type switches. "The dimmer-switch method uses
a single triac, which is a device used to 'chop the wave.' In other words,
of sending a pure sine wave to a motor, it will just 'chop the wave'
- cut it off at its peaks and valleys - so that it doesn't get as much
power to the motor," Mr. Woolsey tells APPLIANCE. "When you
do that you create harmonic distortion, which is really the motor's response
to getting something other than a pure sine wave, and that causes heat
and can also cause an audible noise or a hum," he explains.
"Our product utilizes a patented method of using multiple triacs
and a novel way of wiring a motor so that we can send a 'chopped' wave
only part of the motor instead of the entire motor," Mr. Woolsey
continues. "That allows the motor to run more smoothly, with a better
signal going to the larger part of the motor. The end result is less
heat generation and less sound."
The controller is UL-/CUL-recognized
and is designed for use with Varidigm Definite Purpose Split Capacitor
(PSC) Frame 42, Frame 48, and 3.3-in
motors ranging from 1/20 to 3/4 hp. The controllers are available for
120-, 240-, and 277-V, 60-Hz motors.