由于其高节能性，越来越多的变速、可变输出加热、通风和空调（HVAC）设备单元继续被安装。然而，由于这些功率转换器中使用的半导体器件固有的非线性，提供给电机的电压和电流波形不是纯正弦的，因此含有极高的谐波含量。由于仪表的频率响应、范围、内部阻抗等方面的限制，许多可用仪器无法准确测量这种畸变电流波形的功率或能量。 此外，一些能够测量畸变波形并提供电压和电流总谐波畸变（THD）的仪表考虑了前50次谐波。然而，初步结果表明，在脉冲宽度调制（PWM）驱动的情况下，如果在考虑前50、100和200次谐波的情况下计算驱动馈电电机输入电流的THD，则分别获得19.18%、20.28%和71%的值，这表明前50次谐波的THD是不够的。 此外，目前可用的标准没有考虑谐波的存在，以正确确定效率或分离损耗。关键词:测量，变速电机，电子，控制，波动电压，仪器，测量设备，精度，仪表。引文:1993年阿什雷交易会，第99卷，pt。1.

An increasing number of variable-speed, variable-output heating, ventilating, and air-conditioning (HVAC) equipment units continue being installed due to their high energy savings. However, because of the nonlinearity inherent in the semiconductor devices used in these power converters, the voltage and current waveforms supplied to the motors are not purely sinusoidal and thus contain an extremely high harmonic content. Many available instruments do not accurately measure the power or energy of this distorted current waveform due to limitations in the meter's frequency response, range, internal impedance, etc. Moreover, some of the few meters that can measure distorted waveforms and provide a total harmonic distortion (THD) of voltage and current take into account the first 50 harmonics. However, preliminary results show that in the case of a pulse-width-modulated (PWM) drive, if the THD of the input currents of the drive-fed motor is calculated taking into account the first 50, 100, and 200 harmonics, the values 19.18%, 20.28%, and 71%, respectively, are obtained - showing that a THD of the first 50 harmonics is not enough. Furthermore, currently available standards do not take into account the existence of harmonics for the proper determination of efficiency or separation of losses.KEYWORDS: measuring, variable speed motors, electronic, controls, fluctuating voltage, instruments, measuring equipment, accuracy, meters.