Nice machines ! - One of my clients runs around 30 -40 machines and i have to deal with this question over and over again. In simple terms, impossible to answer just based on KVA off rating plate. Obviously the more power you ask for from the elec supplier, the greater the cost to both the upgrade and ongoing max demand fixed charges. These are the questions facing you to get just the right amount and not to pay more than what you need:
1. What is your baseline current KVA off the supply
2. What is your current power factor.
3. Do you have a load profile of your intended machining for each machine ? Unlikely but i have surveyed similar sites for my client to get this data.
4. Are all the machines using invertor drives for spindle , most likely for Mori Seiki
Broadly your will find that the total power you need is more a function of the material and cycle time of the machines than what is written on the rating plate. e.g. High speed spindle and hard materials, like stainless and titanium will need more power for longer than mild steel.
At this stage i would request multiple KVA quotes for 69 KVA, 138KVA. The lower one can be very cheap as it, hopefully just involves a fuse upgrade, however beyond 69KVA will require an upgrade to the hardware from the electric grid with significant costs.
If the upgrade to 69KVA is around £3.50,
you can get that done and then monitor KVA using power analysers and this may lead to power factor correction solution before moving onto a larger supply.
This is normally a piece of consultancy but anyone who simply adds the three machine tools rating plates and then adds it to your baseline to come up with a max demand figure is doing a dis-service.
The diversity of machine tools can be very large, i.e. you can have 10 machines tools with a combined rating of 300KVA and run them all on a 69 KVA supply.
