Machines or Equipment Resetting

A common problem that can be diagnosed with a good voltage recorder is the resetting of electrical machines that have electronic, PLC or computer controls, where the resetting is caused by the supplied voltage. There are several causes that can precipitate resetting.

High average voltage supplied to the electronics power supply unit (PSU) can cause it to trip out on an 'overheat' fault, likewise low voltage can also cause overheating of the power supply tries to deliver the necessary energy to the electronics.

Low supply voltage can also cause the PSU to drop out as it simply cannot maintain the required output voltage, so will run out of energy and drop out albeit momentarily.

Short duration voltage dips (in the order of a few milliseconds) can cause problems with some electronic control circuitry. The Electrocorder rage use a constant sampling technique to capture events. A voltage logger will record 3 parameter per phase, Vavg, the true root mean square, (TRMS) average over the averaging period you select, it will also record Vmax and Vmin, these are the single highest cycle (50Hz, 20ms period) voltage and the single lowest cycle (50Hz, 20ms period) voltage that was seen during each and every averaging period.

Irrespective of the averaging period set, you always get this 20ms resolution. So if the voltage drops to say 100V for 20ms or more, that value will be recorded. You will not know how many times it dropped to 100V as only one value is recorded, but you will know it occurred at least once, this may be the cause of the resets. If it happens often during the averaging period, then the average value will be dragged down and shown as a lower average.

Typical causes of intermittent short duration low voltages are thing like the starting of large induction motors, arc welding and any electrical activity that has a large starting current.

An intermittent voltage supplied to the PSU can cause a reset, as some PSUs do not have a long enough ride-through, so if the supplied voltage drops (even for a shot period) the PSU cannot deliver energy when it is receiving none or too little from the supplied voltage. This has become more common as PSUs are being built more cheaply with less materials, less components therefore less weight; designers are not building in any appreciable ride-through capability. Intermittent supply or drop outs can occur if the power company is performing network switching operations. It can also be caused by local wiring issues like poor connections or wiring within the premises. There are other causes.

You can use a voltage logger like the EC-1V, EC-2V or EC-3V to record the supply to the machine and look for high, low or intermittent voltage. These loggers can see drop outs of 1/2 to 1 cycle. A cycle is 20ms on 50Hz system or is 16.6ms at 60Hz.

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