Science Forums

# Need help for project

## Recommended Posts

I wish to build energy saving unit for domestic purpose using capaciotrs. Can anybody help giving resourses for circuit diagrams , calculations ?.

##### Share on other sites

I wish to build energy saving unit for domestic purpose using capaciotrs. Can anybody help giving resourses for circuit diagrams , calculations ?.

We need more info than that to be able to help. How do you plan on using capacitors to save energy?

##### Share on other sites

Thanks for responding,

I am planning to put power factor correction capacitor in parallel to mains supply line. I need calculations for capacitor value for entire load.

Will a common capacitor will be enough or separate cap for different loads is required?

What will be advers effect if capacitor is over corrected?

Regards,

##### Share on other sites

I am planning to put power factor correction capacitor in parallel to mains supply line.

To your house? Why would you assume you have a bad power factor - did you have an electrician check it?

I need calculations for capacitor value for entire load.

In order to buy the correct unit?...

Benshaw Automatic Power Factor Correction Products

Or, are you thinking of building your own :doh: ?

~modest

##### Share on other sites

I am not assuming . Unless corrected by a suitable capacitor , power factor of all inductive loads remain approximately 0.65 to 0.7 which can be corrected to 0.95 or more by power factor correction, inturn to reduce bills by that much proportion.

I wish to build my own , but thanks for giving link , I will definately check it.

Thanking you,

Regards.

##### Share on other sites

I am not assuming . Unless corrected by a suitable capacitor , power factor of all inductive loads remain approximately 0.65 to 0.7 which can be corrected to 0.95 or more by power factor correction,

The most inductive loads (such as a blender or washing machine) would have a power factor around 0.75. In an inductive load, the voltage wave reaches peak before the current (sometimes called a lagging PF, because the current is lagging) The opposite is true of a reactive load. Most household items are purely resistive and have no effect on power factor.

Without testing, there is simply no way of knowing what your power factor is. It will change throughout the day and year.

inturn to reduce bills by that much proportion.

Not true.

Energystar:

Power factor correction devices improve power quality but do not generally improve energy efficiency (meaning they won't reduce your energy bill). There are several reasons why their energy efficiency claims could be exaggerated. First, residential customers are not charged for KVA-hour usage, but by kilowatt-hour usage. This means that any savings in energy demand will not directly result in lowering a residential user's utility bill. Second, the only potential for real power savings would occur if the product were only put in the circuit while a reactive load (such as a motor) were running, and taken out of the circuit when the motor is not running. This is impractical, given that there are several motors in a typical home that can come on at any time (refrigerator, air conditioner, HVAC blower, vacuum cleaner, etc.), but the unit itself is intended for permanent, unattended connection near the house breaker panel.

Some good calculations are done on this webpage showing what your savings would be with typical household appliances. The results are summarized on this table. It's pennies per month.

I wish to build my own

The idea behind power factor correction is to shift the lagging current waveform ahead to the voltage waveform. Basically, to get this:

To become this:

Your power factor changes significantly depending on what appliances you are currently running. A power factor correction unit will need to sense the lagging current and know when and how much capacitive adjustment is needed. While that does sound like an interesting electrical engineering problem, it is currently beyond my ability to tell you how to build such a thing.

I am planning to put power factor correction capacitor in parallel to mains supply line. I need calculations for capacitor value for entire load.

If you place the PFC parallel with the load then the load voltage will be almost equal to the source voltage. On the main supply line you would have to worry about transient overvoltage. The capacitor can be in resonance with a high voltage transient resulting in voltage magnification which can easily destroy electronic equipment in your home.

Will a common capacitor will be enough or separate cap for different loads is required?

automatic power factor correction unit is used to improve power factor. A power factor correction unit usually consists of a number of capacitors that are switched by means of contactors. These contactors are controlled by a regulator that measures power factor in an electrical network. To be able to measure 'power factor', the regulator uses a CT (Current transformer) to measure the current in one phase.

Depending on the load and power factor of the network, the power factor controller will switch the necessary blocks of capacitors in steps to make sure the power factor stays above 0.9 or other selected values (usually demanded by the energy supplier).

##### Share on other sites

Thanks to all for helping.

I got lot of information, now I am going to experiment with small load and will feed back if I got some thing positive.

Regards,

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

×   Pasted as rich text.   Paste as plain text instead

Only 75 emoji are allowed.

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×