OVERHEAT MODE
NPG-20/3500 (NPG-20/3500N) generator has 50 Ohm impedance coaxial output
connector and 50 Ohm impedance output cable. If the generator operates on an
unmatched load with an impedance not exactly equal to 50 Ohm, then part of the
pulse energy inevitably reflects from the load, returns back to the generator, and
dissipates in it. The generator can withstand operation with unmatched load, but it
may be overheated in case of long-time operation in such a regime.
OVERHEAT LED (7) lights on in this case and the generator stops the operation.
Please turn off high voltage by HV ON/HV OFF switch (4) and allow fans to cool
the generator for several minutes. OVERHEAT LED (7) lights off after the
cooling and the generator is ready for operation again.
Unfortunately, the matching with the load usually is not exact. To estimate the
portion of the energy reflected from the load please check the amplitude of the
secondary and following pulses by an oscilloscope with a high voltage probe
connected to the load. You should use 500 MHz or more bandwidth oscilloscope
and >20 kV pulse voltage probe, for example, Tektronix TDS 3052C and
Tektronix P6015A probe.
OVERHEAT LED (7) blinks for a short time when you switch on or switch off the
generator by power switch (1) on the rear panel. This is normal and indicates that
the generator control and protection system is in working condition.
MEGAIMPULSE LTD. 10
