Voltage Regulators – A comparison between Solid State and Servo

Voltage regulators stabilise the voltage when it fluctuates, up or down. They are essential whenever reliable power is needed or when normal operation of electrical or electronic equipment is disrupted by the variations. In Kenya, voltage fluctuations have happen on a regular basis with urban city centers like Nairobi having high voltage and more rural locations suffering from low voltage or brown outs.

For manufacturing companies, businesses and medical facilities, voltage fluctuations pose a real threat to business due to damage to equipment, or shorten operational hours. An ideal solution would be a fit & forget solution. One that requires no maintenance and no human intervention once installed. It should be an extension of your normal electrical infrastructure to safeguard your equipment without needing any regular servicing.

Solid state stabilisers have no moving parts and require no maintenance making them the preferred solution for voltage regulator systems. Servo stabilisers however, contain a motorised element. A motor has carbon brushes that can erode or even dust and particles can interfere with their normal operation. They require regular attention and maintenance decreasing the operating lifespan and increasing long term costs.

Servo stabilisers are very old technology. By the inherent nature of their design, they provide a fine output control. Their output accuracy is often as tight as 0.5% Most electrical utilities around the world cannot provide or promise better than +-/5%.

Historically, the voltage supplied in the UK is set at 240V and the supply range is between 226-254V.  Many electrical distribution networks have been put in place to deliver electricity within this range.  Since 1995, steps have been taken to harmonise the UK’s supply specification to 400/230v -10% +6%, which is close to Europe’s supplied voltage.  This remains the current UK position.

Electricity Quality and Supply Regulations (EQS) will harmonise the supply across Europe at 400/230 +/-10% (253V-207V). EN 50160 states that voltage can vary around the nominal voltage in a band of +/-10% for minimally 95% of the time (measured with 10-min integration interval). For LV customers only a 100%-of-time limit is set at +10%/-15% of nominal voltage.

So why insist on +/-1% or better…No reason whatsover. Most electrical and electronic equipment have a tolerance of far greater than this.

Furthermore Solid State/AVR technology is becoming more affordable making the only real advantage of the old SERVO technology, which was lower price, obsolete. The more affordable Solid State, Maintenance free, dust free and noiseless and modern technology AVR will always be the better voltage regulator system for manufacturing, businesses and hospitals.

The Tables below compare the Solid State AVR to Servo

Table 2 AVR vs SERVO comparison