Before answering the question, it is important to know the protection level for PTC is 1330Ω; and for AC motor drive that supports 10.5V of DC voltage, the protection level is 2.4V. In the following figure, impedance for AVI in VFD-E series AC motor drive is 47KΩ and in VFD-VE series AC motor drive is 2MΩ; impedance for ACI in VFD-E series AC motor drive is 100Ω and in VFD-VE series AC motor drive is 250KΩ. With the above information, we can calculate for X. For VFD-E series, the input resistance of PTC is 4.4KΩ.
Technically, VFD-VE series AC motor drive would have greater internal resistance when connected in parallel which means smaller impedance effect. In the following example, since impedance for AVI in VFD-VE series (2MΩ) is greater than VFD-E series (47KΩ), VFD-VE series can be connected in parallel and the recommended range for the resistor is 1Ω to 10KΩ.
