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3 phase vs single phase. What to look for as it relates to…

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3 phase vs single phase...
3 phase vs single phase. What to look for as it relates to power consumption
Submitted: 7 months ago.Category: Electrical
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Answered in 12 minutes by:
11/15/2017
Electrician: Kevin, Licensed Electrical Contractor replied 7 months ago
Kevin
Kevin, Licensed Electrical Contractor
Category: Electrical
Satisfied Customers: 4,355
Experience: 31 years Licensed Electrical Contractor in Illinois, Adjunct College Electrical Instructor, Former Electrical Inspector, Diploma: Digital Electronics, FCC Technician License
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Hello and welcome to Just Answer. My name is ***** ***** I will be happy to assist you with your electrical question.

1) Single phase is commonly used in residential dwellings while 3-phase is mainly used for commercial and industrial power distribution.

2) Single phase is distributed in 120 and 240 volts and commonly in both of these voltages. 3-phase voltage is commonly 208 or 240 or 277 or 480 volts or higher voltages.

3) The total power consumption is dependent upon the amperage or wattage rating of the connected loads. 3-phase voltage distribution is widely used in commercial and industrial applications due to the power efficiency. 3-phase voltage is always preferred for larger electric motors and air compressors as compared to single phase.

4) In summary, as you can see from above, power consumption has many variables that all need to be considered.

Let me know if that helps to answer your question..........Thanks.............Kevin

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Customer reply replied 7 months ago
Does the motor have a minimum size requiremento run on 3 phase? I'm looking to buy a machine. It comes portable with a 19hp gasoline engine or stationary with a motor(maintenance free I was told). The gasoline engine uses about 6-7 gallons in 8 hours. How much power will the equivalent use say in single phase 220v versus 3 phase 220 or 377?
Customer reply replied 7 months ago
Can you send me a wiring diagram from pole to panel box to machine for a 3 phase system?
Electrician: Kevin, Licensed Electrical Contractor replied 7 months ago

1) Motor horsepower are manufactured in many amp and voltage ratings.

2) For example, using amperage values from the NEC motor tables (tables 430-150 and 430-148). Real-world values may be slightly different, but you get the idea. Both are 1Hp, 230V:

Single-phase motor is rated @ 8 amps. 230V x 8A = 1840 watts.

3-phase motor is rated 3.6 amps. 230V x 3.6A x square root of 3 = 1434 watts.

So, at full load, the 3-phase motor uses 22% less power to do the same work.

3) A typical 3 phase motor circuit will contain 3 separate hot wires (1 wire per phase) and an equipment grounding conductor. A 3-pole circuit breaker is installed in the panelboard. Downstream of the 3-phase panel, a disconnect is required prior to wiring to the motor.

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Customer reply replied 7 months ago
Can you send me a diagram of what this should look like as explained in #3?
Electrician: Kevin, Licensed Electrical Contractor replied 7 months ago

1) I can provide a diagram, but need additional information as follows:

A) Is there a utility or a customer furnished transformer installed to step up or step down voltage or is the voltage 230 volts 3-phase and existing at the panelboard? Is the panelboard readily wired up for 230 volt 3-phase?

B) Is the 3-phase voltage originating from a delta or a wye system?

C) What is the FLA (full load amp rating) on the motor? Look at the motor nameplate rating. I need the FLA amps of the motor to size the circuit conductors and circuit breaker and the fusible disconnect switch?

D) Will the motor circuit breaker be controlled from a main switch gear or from a main panelboard or from a sub-panel?

E) Will the motor circuit contain a "solid neutral"?

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Electrician: Kevin, Licensed Electrical Contractor replied 7 months ago

1) Also, how many horsepower is the motor and the supply voltage?

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Electrician: Kevin, Licensed Electrical Contractor replied 7 months ago

1) It is getting late and I'm off to sleep for awhile. Get me the info and I can work on creating a diagram later on today.

Thanks...........Kevin:)

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