The single-phase motor was run at the same speed points as the previous test on both a variable frequency drive and a TRIAC control. To compare AC control to DC inverter control, two different fans were chosen – an AC single phase and a DC – which had the equivalent performance, but not the same as the previous two fans. The single-phase motor was driven with a TRIAC control under the same test conditions as above. This way the efficiency of the variable frequency drive is also accounted for in the power consumption. The power consumption was calculated by taking the true RMS voltage reading on the input line and the true RMS current on the input line and multiplying them to give the power input to both the controller and the fan. The pressure was monitored through a wind tunnel and held constant for each speed setting during the testing to ensure that the load on the fan was constant and the flow rate was equivalent. These two fans were controlled from 100% speed to 40% using a variable frequency drive. This setup, shown in Figure 1, was used to test the systems described in Table 1 below.įirst, two fans with equivalent performance (flow & pressure) were selected in single phase and three phase 208VAC. For each speed setting, the pressure was held constant and the input power was monitored using a true RMS voltage meter and ampere meter. The fan under test was loaded in a wind tunnel while its speed was monitored with a strobe. This comparison assumes that only single-phase AC power is available. The test results discussed here attempt to normalize some of the inherent differences and make an equal comparison for using different types of motor controllers.
With the wide range of control technologies available (TRIAC control, variable frequency control, and AC to DC inverter control), determining the most energy efficient solution can be complicated. It is generally understood that adding speed control to a fan will save energy when the fan is operating at less than full speed thus improving motor efficiency.
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