Resource Library

What is the difference between a voltage regulator and a Dynamic Voltage Restorer (DVR)?

Both are used to mitigate the effects of voltage dips. Dips are characterised by the depth – the retained voltage – and the duration. Short and deep dips are best served by a DVR while long and shallow dips are the province of the voltage regulator.

A voltage regulator has no energy store. It has a transformer secondary winding in series with the supply. When the input voltage moves outside the tolerance band the primary of that transformer is driven to boost, or in anti-phase to reduce, the voltage appropriately. Because the load voltage is kept constant, the power to the load is constant so, when the input voltage falls, the input current increases. The current capability of the supply and the device itself limits the working range to about +/-30% of nominal voltage.

A DVR has an energy store, so requires no additional input power (in the short term) to boost the voltage during a dip. A DVR can correct a dip to 0% retained voltage. But the DVR has a limited energy store and so is suitable for short-term effects only – it cannot correct for long term under voltage, for example. Also, the store has to be recharged between events so it is not suitable multiple dips are expected frequently. Typically, DVRs use super capacitors, large secondary batteries or high-speed flywheels as energy stores.

Unsurprisingly, DVRs are more expensive than voltage regulators.

In long strip roofing what is the maximum length of a bay?

This depends on the pitch of the roof. For 3-4 degrees 14.6m, for 4-10 degrees 11.0m, for 10-30 degrees 9.7m and for over 30 degrees 8.1m.

Why is copper the preferred material for busbars?

There are several reasons. Firstly, the bars are more compact because copper has a higher conductivity than aluminium. Secondly, it is much easier to joint copper. A hard, highly insulating oxide grows very rapidly on the surface of aluminium, making it very difficult to make good reliable joints in the field. On the other hand, the thin oxide layer that forms, more slowly, on copper is not an insulator so jointing is simple. Finally, copper is much stronger than aluminium, less susceptible to creep and better at withstanding short circuit current forces.

What is the history of copper tubes with aluminium fins?

Condenser coils with round copper tubes and aluminium fins have been a winning combination for ACR coils for many years. Manufacturers enjoy the assembly advantages provided by these components while technicians find it easy to join and repair copper tubing in the field. More importantly, this well established technology has a proven record of durability in the field resulting in a high level of customer satisfaction.

What is the main advantage of small diameter tubes for the design of air conditioner coils?

Smaller diameter tubes allow for more effective heat transfer.

Is copper an essential element?

Yes, copper is as vital as calcium, iron and zinc. An adult needs 0.9mg of copper every day to maintian good health. Nuts, seafood, wholegrain cereas and offal are good sources of copper and a balanced diet should provide adequate copper.

What is the minimum pitch for long strip copper roofing?

3 degrees.

Is hot patination of copper using ferric nitrate allowed? If so what are the safety implications?

Yes, it has been used for many years. However the nitrous oxide fumes given off when absorbed into surrounding fabric create a fire hazard. Also energy is used in the heating process. Better to patinate cold or use prepatinated copper.

What material is recommended for underground pipe fittings?

Gunmetal or dezincification resistant brass.

Will commercial grades of copper become hard (like steel) if they are cooled rapidly after heating?

No. Copper is not susceptible to precipitation hardening.