Fuse Selection

Consult local electrical Code. If none, consult some other local/regional electrical Code.

Go to school.

Consult the proper code.

Google NEC.

Ask an electrical technician.

Google fuse and circuit breaker sizing.

Good luck.

Use British Standard 7671. How about asking Santa for a copy?

Don't forget to ask for the BGB (green copy).

by attending a structured training programme on the subject.

The proper technique is to go to school and learn the fundamentals of electricity. This should teach you which parameters are critical for fuse selection and how to calculate or measure these parameters. This approach will also provide you with a useful skill set in your career, if you do your own homework.

The next technique is to visit fuse and circuit breaker manufacturer's web sites and read the application notes that these web sites have. The problem with this approach is that these sites expects only people that have a fundamental knowledge of electricity in the first place.

The next technique is to hire or pay for the services of somebody who did succeed in doing one of the two above techniques. People you can hire are electrical engineers, electricians, and electrical technicians. Payment should be negociated before the rendering of service. Payment can be in the form of currency, barter, or any of a number different favors. These favors don't have to be salacious, but if you both agree they could be.

So if you go through the effort of learning electricity and how to do your own work, you can become of the receiver of payment.

GA, well put redfred. It's obvious that this person missed out on the class notes when they covered the subject of circuit protection

"How to select the fuse rating for the particular application or for the motor ? how to select the circuit breaker and relays for the individual equipment?"

These are not simple questions...First you must determine that you have adequate power supply, that the voltage, hertz rating is correct, then the wiring must be sized to accommodate the anticipated load, with an acceptable margin... then the overcircuit protection can not exceed the wiring capabilities in this application...usually these circuits are shared with other loads, you must determine if the appliance in question requires a dedicated circuit, or will share a circuit with other uses...If this is the case an additional fuse device may be required for the appliance in question... Most electrical appliances have a electrical rating tag attached, but usually these only give a portion of the information needed, you must be able to calculate the rest on your own...Certain grounding or other special requirements exist for certain applications...Motors typically require 2 to 3 times running current on start-up, your fusing must be delay type to allow this but still be close enough to motor load usage to protect the motor, but not so close as to overheat...So you can see this type of work requires a great deal of knowledge and should not be attempted by laypersons, such as yourself...One small mistake can cost the life of an innocent bystander...

for fuse selection = motor hp x 1.5

Only for 3-phase motor voltages around 460, and not very precise even there.

Dear friend,

It should be Motor FLA * 2.5 times will be the fuse rating. This will match TYPE 2 Coordination.

Its easy to pick a fuse for a motor. Take that one. The one I'm pointing at. It'll work just fine for that motor. Yes, I'm pointing to that motor. Can't you see.

The function of the fuse is to protect the conductors.

Select fuse according to the conductor size not the applied load.

Conductor selection is dependent on the load.

Well educate yourself with the link below. Or hire an electrician.

http://www.omega.com/auto/pdf/REF_FuseSizingGuide.pdf

Good luck, and remember the fuse protects the feed not the load.