Vega Customer Applications Manual
Section 9 - Functional Notes
Rev. A3: October 2003
Page 30 of 48
capacitors charges to a set level the thermistor is "switched out" via a relay and current will become the nominal input
current which depends on load. Actual nominal input current = (actual output power/efficiency)/Input voltage.
If circuit breakers or fuses are used in a customer system, ensure they are capable of handling a 40A turn on surge.
They should be of time lag or slow type. Breakers should be type C breakers to handle the inrush.
The Fuse.
The input fuse is INTERNAL to the PSU and is not user accessible. It is designed to protect the PSU. If the fuse has
opened, there is something wrong with the PSU to have caused it and the PSU should be treated as "failed".
Leakage current.
The leakage current is measured as the current from L&N to earth at 264VAC input and 63Hz. It is mainly due to Y
capacitors. These are connected in the internal filter from Live and Neutral to Earth and to provide a path for high
frequency common mode noise to return to it's source.
Surge protection
There are transient suppressors fitted to ensure Vega is protected against surges and spikes of voltage on the input
lines. The level of protection is as described in the EN61000-4-5 specification.
Output Efficiency.
The efficiency is a function of output voltage, load and input voltage. Efficiency is worse at lower loads and output
voltages. Also a 450W converter which is providing only 200W of output power will be a few percent lower in efficiency
than the listed specification.
Efficiency decreases as the input voltage decreases
Graphs of efficiency vs both input voltage and output power are available on request.
Overvoltage Protection.
All Vega output modules have two levels of overvoltage protection.
Tracking overvoltage protection.
This is the lower of the two levels, the overvoltage setpoint will track the voltage set at the sense terminals. This will be
the voltage at the output terminals of a module, if connected local sense or the voltage at the load if connected with
remote sense.
Example, If a module is connected in remote sense and set to give 5V at the load then the overvoltage protection point
will be at 124% = 6.2V measured at the load.
Example, If a module is connected in local sense and set to 12V, the OV point will be 14.9V measured at the output
terminals of that module.
Stage 2.
Each module also has a second maximum threshold at which OV functions. This is not tracking but fixed at a level
higher than the maximum voltage than the module can be adjusted to. See the specifications for each module.
