Generator compatible is a sentence, not a specification. A theatre that dips when the sterilizers start needs three documents before any purchase order is credible: a site power condition sheet filled in by the hospital with measured values, a per-model ride-through declaration from the factory that states what the table and the light do at those values, and an on-site dip test at commissioning that records the equipment\u2019s behaviour and gets signed. The site sheet comes first. Until the hospital knows its own residual voltage, duration, recurrence and generator load, it cannot judge any factory claim, and the factory cannot be asked to meet a condition nobody has written down.<\/p>\n
Immunity testing and site compatibility are different claims. A unit that passes the electromagnetic immunity tests in IEC 60601-1-2, including the voltage-dip and short-interruption tests of IEC 61000-4-11, has demonstrated that it meets the standard\u2019s performance criteria at the standard\u2019s test levels on a laboratory source. That is a laboratory statement about a defined stimulus. It says nothing about what happens on a hospital generator when a sterilizer bank draws starting current, because that event has its own depth, duration, repetition and source impedance.<\/p>\n
The two claims can be separated cleanly by asking for the test conditions. What voltage was the source? What was the residual voltage as a percentage of nominal, and for how many cycles? Which performance criterion was reached, A, B or C? Was the unit powered from a generator or from a programmable AC source? Was the equipment under load, and were its motors or its battery being charged at the time? A declaration that answers those questions is a specification. One that says compliant does not.<\/p>\n
The criteria deserve a sentence each, because the difference decides clinical acceptance. Criterion A means the equipment behaved normally. Criterion B means a temporary degradation that corrected itself without operator action. Criterion C means the operator had to intervene, reset or restart. In a theatre, criterion C during an operation is the case the whole document set exists to prevent.<\/p>\n
The sheet has six fields, and every one of them is a measurement rather than an opinion. Nominal voltage and frequency. Residual voltage during a real event, as a percentage of nominal. Duration of the dip in milliseconds or cycles. Recurrence, meaning how many events occur within a defined period and how closely they cluster. Generator load and source condition at the time of the measurement. And the point in the distribution where the measurement was taken.<\/p>\n
The measurement method matters as much as the numbers. A power quality recorder at the theatre\u2019s distribution board captures the event as the theatre sees it. A logger at the equipment isolator captures it closer to the load. Both are useful and they are not interchangeable, because voltage drop along the feeder is part of the problem. Record at the board if the question is what the building delivers, and at the isolator if the question is what the equipment receives.<\/p>\n
Timing is the next trap. A single weekday morning sample will miss the event that matters, because the dip is caused by a specific load switching on. Measure across a full working day that includes the sterilizer cycles, and annotate the recording with what was running. If the hospital has never measured, the honest entry on the sheet is not measured, and that entry is itself a finding: the requirement is being specified from assumption.<\/p>\n
Ask for one page per model, in a fixed format, so two suppliers can be compared. The page should state the supply envelope the unit is designed for, the hold-up time of its internal supply, and then the behaviour at a series of defined events, each with the event written as percentage of nominal voltage and duration in cycles.<\/p>\n