I purchased a "hospital" isolation transformer originally designed to isolate failures on the secondary winding of the isolation transformer from unknown equipment tied to the primary winding of the isolation transformer. A Hospital Isolation transformer ties earth ground to the secondary and to the grounded part of the outlet so that it appears to be identical (to an outlet checker) to the outlet to which the primary winding is connected. The transformer isolates any secondary winding load circuit failure from being seen by other devices attached to the power feeding the primary winding.
(that understanding was conveyed to me via Larry (search isolation W0QE YouTube) with his awesome simulation).
I want to convert the "hospital" isolation transformer to a "technician" isolation transformer in which all earth ground exposures are removed from any equipment connected to the secondary side of the isolation transformer. The conversion has been amply stated elsewhere in this and other forums. I will not repeat it here.
There is one feature that came with the hospital isolation transformer that I do not understand and hence can not consider if I should retain it or not in my effort to make the conversion of Hospital to Technician isolation type transformer.
That feature is a delay circuit that exists between the off/on power switch and the primary winding of the transformer. The timing is 0.5 second which
suggests that at least 30 full cycles of 120 VAC take place before current is allowed to feed the primary winding.
I can only think of one use for the delay. If the "hospital" isolation transformer lost power to its primary windings while the switch was "on", then it is
highly probable that a great number of devices are attached to the circuit that lost power. Hence when power is restored, the surge of current to start
all the low power devices in a hospital environment are likely to have completed their power up sequence well within the 30 full cycles. Why that is important is not clear to me as the transformer is a huge inductor which resists current surge (my understanding). Maybe the delay is to protect the
electronic filtering of input power of attached medical equipment from any repowering sequence that might occur after sudden power loss.
Any ideas? I am just making a wild guess.
bil
(that understanding was conveyed to me via Larry (search isolation W0QE YouTube) with his awesome simulation).
I want to convert the "hospital" isolation transformer to a "technician" isolation transformer in which all earth ground exposures are removed from any equipment connected to the secondary side of the isolation transformer. The conversion has been amply stated elsewhere in this and other forums. I will not repeat it here.
There is one feature that came with the hospital isolation transformer that I do not understand and hence can not consider if I should retain it or not in my effort to make the conversion of Hospital to Technician isolation type transformer.
That feature is a delay circuit that exists between the off/on power switch and the primary winding of the transformer. The timing is 0.5 second which
suggests that at least 30 full cycles of 120 VAC take place before current is allowed to feed the primary winding.
I can only think of one use for the delay. If the "hospital" isolation transformer lost power to its primary windings while the switch was "on", then it is
highly probable that a great number of devices are attached to the circuit that lost power. Hence when power is restored, the surge of current to start
all the low power devices in a hospital environment are likely to have completed their power up sequence well within the 30 full cycles. Why that is important is not clear to me as the transformer is a huge inductor which resists current surge (my understanding). Maybe the delay is to protect the
electronic filtering of input power of attached medical equipment from any repowering sequence that might occur after sudden power loss.
Any ideas? I am just making a wild guess.
bil