Variable transformers put to the test

REO has introduced a range of variable transformers, with reversing motor drives and cam-operated limit switches.

REO has introduced a range of variable transformers, with reversing motor drives and cam-operated limit switches.

Additional switches can be incorporated for indicating other positions, such as zero volts, and the cams have a built in worm and worm wheel gear for fine adjustment.

For applications that require a fast response time it is possible to fit DC servomotors.

The transformers allow the user to generate a true sinusoidal power source that can be varied from an analogue signal, and can simulate mains fluctuations, including overvoltages.

Three- and single-phase variable transformers are available for testing switch-mode power supplies and frequency drives to establish if they can operate within the voltage range stated by the manufacturer.

A standard variable autotransformer can provide a 0-270V output from a 240V mains supply, without sinewave distortion.

The transformers can also be built to operate on frequencies of between 50 and 400Hz and the power range extends up to 1MVA.

REO produces a range of electronic control modules, which are available off the shelf, and are suitable for most control applications such as voltage regulation or voltage profile following, generated from a PC.

All controllers include inputs for analogue current or voltage set point signals and there is also provision for front panel adjustment from a potentiometer.

Trimmers are provided for setting sensitivity and response (PI characteristics).

On some modules there are also input terminals for manual/auto control selection, raise/lower buttons and a go to zero volts signal.

A trimmer is provided for scaling the system to match the effective output voltage.

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