I have a PC and an external HDD switchmode power supply both connected to the UPS battery backup outlets. The external HDD supply is ungrounded but the PC is grounded. There is leakage current between the USB connector of the external HDD and the PC case. It lights a neon tester when touched between these two points. The rated leakage current is 250 microamps at maximum voltage and frequency. Normal AC power uses true sine-wave but battery backup uses modified sine-wave similar to square-wave. Does the modified sine-wave cause higher peak leakage currents when switched to battery mode? I don't have an oscilloscope to see what the leakage current looks like while on battery. Can this higher peak current cause a shock when touching the USB connector and the PC case at the same time while the UPS is on battery mode? When the USB cable is held next to a t-coil equipped hearing aid while on battery there is a buzzing sound which does not occur while on AC mode.
- posted
17 years ago