Load-Sensing Voltage Regulation – LSV – 15

Especially designed for CNC applications and for variable frequency drives. Enables the converter to maintain balanced output voltages over a wide load range.

The Load Range monitoring and adjustment control maintains the converter output voltage within a balanced range up to the maximum output of the converter. Its purpose is to compensate for a load which is insufficient to bring the converter output voltage into balance with the utility supplied voltage in order to prevent excessive imbalance of currents within the load.

In a rotary phase converter, the voltage of the manufactured leg varies according to the amount of connected load. Under no-load conditions this voltage will be within 5% of utility voltage. As load is applied, the manufactured phase drops rapidly into balance with the other two lines as the load increases to about 25% of converter capacity and remains there over the remainder of the range. Under most load conditions all three phases will balance to within 2-5%, which is acceptable for nearly all induction motors.

In applications involving multiple motors, the load varies as different motors come on and off line. The converter must be sized for the largest load, but there are times when only a small portion of the load is connected. Under this condition the manufactured phase voltage is too high and could cause nuisance tripping of the small motors. When the large motor comes on line, the voltage is balanced and the problem goes away.

The Load Range Controller monitors the manufactured phase current and operates a relay when this current moves above or below a preset level. When a portion of the load is added to or disconnected from the converter, the manufactured phase current changes. The Controller determines whether the new current level is outside of the allowable range. If so, the relay adjusts the converter output bringing it to an acceptable level within a short time to balance the current before the load is affected.