"Most normal inverter duty motors can be driven from 10 or 20 Hertz without cooling up to 120 Hertz," explains Chris Popp, spokesperson for DieQua Corp., Bloomingdale, Ill. "Above 60 Hertz, however, the torque generated begins to break down, reducing the effective speed range.
Often, there's no choice but to specify a larger motor."
A new alternative is DieQua's Watt Drive EUSAS 4-pole AC motor, which provides full torque throughout its speed range, up to 3500 rpm.
Available in sizes from fractional to 100 horsepower, the EUSAS
features an innovative winding design that allows increased input current, thereby extending the constant torque range to 120 Hertz. As a result, the motor size can be cut by up to half when doubling the input speed and doubling the reducer ratio without compromising the application's output speed or torque requirement.
Although a 440- to 480-volt power source and a basic programmable inverter rated at the normal horsepower is required to achieve these benefits, "the bigger inverter would be needed to drive a standard motor anyway so there is no downside to taking advantage of this less costly smaller motor alternative," Popp
also provides a wider speed range, which is important in applications where a speed variation sometimes requires operation under 20 Hertz, such as driving the larger of several roll sizes or when slower conveyor speeds are needed.
"By using a gearbox with twice the ratio than would normally have been selected, the EUSAS motor can produce both the top-end speed required as well as a lower output speed before external cooling is necessary," Popp