ASHRAE Journal - September 2019 - 35

ASHRAE - CELEBRATING 125 YEARS

Development of the alternating current motor revolutionized the HVAC&R industry by providing a less
complicated, less expensive way to operate equipment,
and ac motors could be turned on and off using automatic controls. Also, these motors were developed in
smaller sizes, opening the door to packaged equipment
development for heating, refrigeration and later, air
conditioning.
By 1920, most developed urban areas had ac power
available for homes, businesses and factories. Polyphase
ac induction motors, as well as synchronous motors,
were available for factory and large commercial equipment. Homes and small businesses were served by
single-phase electric service within a voltage range of
104 to 230 volts. For those customers, a number of small
single-phase induction motors were soon available for
appliances, including refrigerators, and for oil burners,
ventilating fans, etc. At ﬁrst the need was served using
so-called "split-phase" induction motors; however, the
need for higher starting torque for refrigeration compressors, etc. brought about invention of capacitor-start
and repulsion-start motors. The repulsion-start induction motor proved to be a solution to a vexing problem
when motor-powered HVAC&R equipment was introduced into household use. Well into the 1930s, most
homes were wired with 30- or 60-ampere service. With
such skimpy capacity, it was common for the lockedrotor (starting) current of a refrigerator to cause the
line voltage to drop precipitously, dimming lights and
often blowing a branch circuit fuse (which were usually
15-amp quick-blow fuses). The solution was to use the
repulsion-start motor, which could develop very high
starting torque at low line voltage using less current
than other types of motors. Repulsion-start motors were
available from 1/8 to 25 horsepower and were the preferred motor type used for HVAC&R in that power range
until they began to be supplanted by capacitor-start
motors beginning in 1930 (Figure 2).
Over time, electric motors were continually improved
by reducing weight and relative cost while increasing efﬁciency, especially in the last 25 years. And now
we have variable-frequency drive motors that allow a
level of energy efﬁciency and control that would amaze
the engineers of the early 20th century-we are well
aware of that within our engineering profession. What
about everyone else? Outside the community reading this essay, the "24-hour stationary engineer," i.e.,

FIGURE 1 125 years ago, electric power was being introduced in cities, replacing
gas lighting. (From: author's personal collection, unattributed source).

FIGURE 2 The repulsion-start induction motor was widely used until the 1930s for
high-starting torque applications such as refrigerators in homes with skimpy electric service. (From: The Heating and Ventilating Magazine, July 1927, p. 189).

"the electric motor," serves us silently, unobtrusively
and with increasing efﬁciency as applied in heating,
refrigeration and air conditioning. And that is quite an
accomplishment!
That progress in electrical development opened the
door to more innovations we also can't live without.1
S E P T E M B E R 2 0 19

ashrae.org

ASHRAE JOURNAL

http://www.ashrae.org

ASHRAE Journal - September 2019

Table of Contents for the Digital Edition of ASHRAE Journal - September 2019