nergy costs in the UK have risen significantly over the last few years, with non-domestic users facing price
increases from 12.32 pence kWh in 2018 to 25.50 pence in Q4 2024, which the British Chamber of Commerce calls ‘an unsustainable increase of over 160%’ Energy inefficiencies – often hidden when voltage fluctuation is an issue – mean unnecessary energy spend, with the potential for damage to vital equipment.
The nominal supply from the grid is 230V, with a tolerance of -6% to +10%, meaning that, legally, supply can be anywhere between 216V and 253V. Sites close to a substation will often receive a higher voltage while those further away may receive a lower voltage. Voltage can also fluctuate depending on demand across the network at any given time. For businesses, these fluctuations can lead to significant inefficiencies – and costs. Globally, electric motors and motor-driven
systems account for 70% of industrial electricity consumption, with energy costs for one year’s operation equating to ten times equipment purchase cost. In the UK and Europe, most new motors must meet IE3 (Premium Efficiency) standards. However, particularly in older factories and across heavy industry, motors pre-dating these regulations are still in service. In these circumstances, site voltage fluctuations can severely impact efficiency. Where there is high voltage, the motor’s magnetic field is stronger than needed, increasing energy losses and reducing efficiency. Where voltage is below nominal, the motor must work harder to maintain required output, increasing current in the rotor with higher resistive losses. Both scenarios lead to unnecessary stress, which can mean additional maintenance and a shorter motor lifespan, with wasted energy and higher energy bills. A Variable Frequency Drive (VFD) is a common
means to achieving more stable voltage. However, VFDs can also be impacted by grid voltage fluctuation. At low voltage, more current
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is forced to flow through the VFD’s components, increasing conduction losses and generating additional heat. In the high voltage scenario, switching losses in the VFD’s electronics – when transistors turn on and off rapidly to regulate voltage and frequency – are increased. Prolonged exposure to high voltage can degrade key components, which can shorten the VFD’s lifespan, meaning unnecessary spend and devaluing the initial investment.
To establish whether VO will benefit your site, it’s important to understand your different load types. Where voltage-dependent, i.e. where power consumed changes with the square of the supply voltage, VO delivers the greatest benefits. Where loads are voltage-independent, a fixed output is maintained regardless of supply voltage. Savings and efficiencies will be lower in this case, but voltage-independent equipment can still benefit from more stable operation and reduced stress. In practice, many sites have a mix of voltage-dependent and -independent loads. For example, a large
Stuart Little
VFD-controlled motor unit may be combined with smaller, uncontrolled, motors or pumps. In general, sites with high energy
consumption, variable loads and sensitive equipment benefit most from VO. Energy- intensive sectors, e.g. food manufacturers, chemicals and pharmaceuticals, and paper and packaging production, together with businesses reliant on heavy machinery, are all under particular strain in the current energy crisis. And, where companies have invested in CNC for business growth and productivity, a stable voltage is critical – to protect that investment and ensure the smooth running of production
Sites with high energy consumption, variable loads and sensitive equipment benefit most fromVO
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