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Sophisticated computer systems sometimes use diesel engine driven generators for backup in case of mains failure.
Where our CVT’s are used for power conditioning in the normal mains mode it is desirable to take advantage of the CVT performance when using the generator.
These notes provide some guidance on the potential problems which can be met together with solutions.
Some generators do not refer the low side of the output to earth. This MUST be tied down to avoid damage to any of our larger catalogue units which have double primary shields.
Care must also be taken that the generator neutral is not connected to the CVT output low.
All ferroresonant devices are frequency sensitive.
The generator must run close to 50 Hz for the unit to operate correctly.
Unfortunately the speed/output voltage curve for the generator goes the same way as the CVT so speed should be adjusted at actual running load.
We publish a curve for the effect of frequency variation in our CVT Handbook hb001.
Short term off-frequency operation will not damage the CVT.
The output from the CVT will be out of phase with the input in cases where the generator supplies other equipment directly some care is needed if a phase sensitive
triac firing circuit is installed.
Unless phasing circuits are fitted all circuits should use ‘break before make’ contactors and enforced supply separation.
Some thought needs to be given to the Regulations regarding out of phase supplies
in the same area.
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