how to control maximum kva demand using logic relay

A normal light chaser circuit should work with time adjustment.

You are being charged for a KVA demand by the utility. This demand is determined over a specific time period, usually 15 minutes or 30 minutes. The starting of the motor would not show up in this time period. The KVA demand will however be registered during the time period it is running. You need to determine the power factor of the load from the utility. You can install a capacitor bank at the main to improve the PF or you can install capacitors on each of the motors. Be carefull if you are using variable frequency drives. Capacitors and drives do no mix well.

Dear guest,

In addition to wareagle comments, an additional billed amount that covers the difference between the power a costumer expects to have available and the energy that the customer actually uses. Demand charges, occasionally referred to as capacity charges, are typically calculated based on the difference between a customer's peak energy use during a billing period and their nominal use(normal or hour-to-hour use) during the same period. if the customer expects to have substantially more power available to them than they actually use, then the demand caherge is applied to cover this difference.

Demand charges are not means of gouging customers by charging for unused energy. Instead they are means of ensuring that the customer can have larger-than-normal supplies of energy available to them at a moment's notice.

As you mentioned you want to design a circuit to control starting of large induction motor maybe you are reffering on "soft starter" which is now very much available in the market, and you are very right since soft starter control provides smooth, stepless accelaration of your motor and load while controlling inrush current and starting torque, however this is only one step in achieving your objective to get rid out of paying "penalties caused by excess kva" as you claimed. there are more opportunities from your plant for sure that causing this factors and can be improve with out adversely affecting your company production.

I can help you on more ways and for sure we can achieve to drop your energy cost from the range of 15% to 30% with zero investment. why let continuously drain your company money into drain? you can manage it. It is very rare to have an plant employee to become concerned on energy bill. should you need more help how to reduce your energy cost, PM me your email add and I can send you more detailed on how you can achieve more energy reduction.

Kind regards

Roman

Hello Mr. Roman,

I am most impressed by your writing. Can you please send more detail about energy reduction. My mail ID is uvaraj.govindaswamy@wipro.com

Uvaraj.G

Dear Mr Uvaraj. G

I sent you email on the email add as mentioned above, please go and check.

Kind regards

Roman

Dear Mr.Roman,

I Haven't reveiced any details. Could you send it again

Regards,

Uvaraj.G

Yes, you are correct. In our company we could save up to 26% with zero investment by voltage optimization method. Sequential relay (available with API, Bangalore) along with some interlocking control it is possible that all machines do not start at a time. Soft-starters also very good where one will have to start big motors. VFD on air/ gas compressors & injection molding machines help reduce power bills.