VDC PREVENT PRODUCTION DOWN TIME CAUSED BY MOMENTARY VOLTAGE SAGS.  

The reliability of electrical power to industry is in general very high, nevertheless, voltage sags or dips do occur. These instabilities are caused by short circuits, lightning strikes on overhead power lines and heavy load switching. The duration of such faults is generally shorter than one second. Power Quality data shows that voltage sags with a maximum depth of around 50% constitute 92% of all events.

Most plant can ride through these voltage dips by virtue of their mechanical and electrical inertia. However, this is not the case with electrically held-in contactors and relays that control the machinery. Contactors typically drop out from 5ms to 20ms after the start of a voltage sag with a depth of 32% - 47%. Each short voltage dip now becomes a power failure and the plant must be restarted. This can be complicated, time-consuming and costly.

VDC is designed to maintain the switchgear control voltage during voltage sags, effectively keeping the plant connected. The stored electrical and magnetic energy is allowed to flow, supporting the mechanical inertia of the machinery. When the power recovers after a short voltage dip, the plant is still running at near synchronous speed, the inrush currents will be small and the stress to the system minimal. The VDC provides an economic solution for users who need their equipment to comply with the SEMI F47 standard for voltage sag immunity.

• No batteries; no maintenance.

• Fast compensation.

• Able to withstand high inrush currents.

• Small footprint, easy to retrofit.

• Support exceeds SEMI F47 standard requirements.

• Handles inductive and low power factor loads.

Losses incurred by these power quality events far outweigh the cost of installing the VDC and investment payback is achieved in a short time.