Three-phase electricity with a pen to measure no electricity with a multimeter but there is a voltage what reason?
First of all, understand the three-phase voltage three-phase voltage is different from our family commonly used single-phase electricity three-phase voltage between the phase and phase line voltage of 380V, commonly used in dragging the motor three-phase machinery and equipment, etc., if the three-phase voltage of a phase phase will lead to instrumentation can not be operated, or even burned.
So if we feel that the three-phase voltage problems, we must immediately use the multimeter to measure the line voltage, if they are 380V, and the line to ground without a short circuit can be used normally, it is not recommended to use the pen to measure 380V, first of all, the quality of the pen varies, and some pens can not even measure the voltage of 380V.
Some pen range is relatively small, if more than his range will not display or display alarm, we mistakenly believe that this with the phase line has no power or fault, played a misleading role, so we try to use a multimeter to measure the line voltage measurement.
In addition to problems with the pen, measuring voltage, there may be this phase and grounded short circuit, if the real short circuit with the grounded pen is sometimes measured with the familiar voltage, but instead of using the multimeter to measure the line voltage can be displayed when the voltage value, the voltage value displayed at this time is very likely not 380V, it is likely to be 220V.
Of course, there is also a possibility that we misuse, inaccurate measurement points, such as a three-phase AC contactor, it is likely that three-phase AC contactor in the three main contacts in a contact problem, resulting in the line does not work, however, we are measuring the lower end of the AC contactor, so the lower section of the main contact is certainly not electric.
We mistakenly think that one of the three-phase no electricity, in fact, measuring the main contacts above the three-phase is normal, just that we do not have a thorough measurement, as a maintenance electrician must be well considered with the appropriate ways and means of checking the line, so as to ensure that the electricity safety equipment operation.
So we are measuring these voltages, we must accurately select the tools, and must find the right measurement point, to avoid because the measurement point or tool selection is not big lead to line downtime equipment shutdown.
