CAN and WILL BE ALLOWED TO are different questions.
Whether or not the motor CAN be started across the line will depend on the available short circuit current (SCC) at your location on the local utility's power distribution grid, and the rating of your service transformer. Check with your utility company. It may be possible to start the motor across the line, based on the transformer rating, but if there is not enough SCC, the utility will not allow you to connect the load without a starter or variable frequency drive system.
20 kw
There is no such thing as a 'phase-to-phase' voltage; the correct term is 'line-to-line' voltage. Whenever you mention a value of voltage for a three phase system, it is considered to be a line-to-line voltage unless it is stated clearly that this is phase voltage (line to neutral) voltage.(The reason that there is no such thing as a 'phase-to-phase' voltage is because phases exist between, or 'across', line conductors or between a line conductor and a neutral.) That is a world wide practice for electrical power engineers.
It depends how they are connected. If they are connected between line conductors then they are measuring line voltages. If they are connected across phases then they are measuring phase voltages.
No, three phase motor overloads just monitor the motor's lines for an overload. Once detected the circuit holding the magnetic starter in will drop out and take the motor off line.
The voltage you are referring to is a 'line-to-line' voltage ('line voltage'), as there is no such thing as a 'phase-to-phase' voltage.480 volts. In real life, the voltage will vary slightly by up to 3% (14 V) on a properly sized circuit. Line to neutral will measure 277 volts, plus or minus 3%.
YES. USE THE NORMAL DIRECT-ON-LINE OR ACROSS-THE-LINE STARTER.
Across the line starter has a large inrush current.
By connecting a voltmeter across pairs of line (not 'phase'!!!) conductors, and between any line conductor and neutral.
20 kw
The phase when chromosomes line up across the middle of the cell is called metaphase. During this stage of mitosis, the chromosomes become attached to the spindle fibers at the centromeres and align along the equatorial plane of the cell.
Line to line voltage is not the same as line to neutral voltage because line voltages are 120 degrees apart. They are related by: Line to neutral voltage * tan (120 degrees) = Line to neutral voltage * 1.73.Additional CommentFor delta-connected systems, the line voltage is the same as the phase voltage.For wye-connected systems, the line voltage is larger than the phase voltage by a factor of 1.732. The reason for this is as follows:Because any two phase voltages are displaced from each other by 120o, they must be added vectorially, not algebraically, to find the line voltage. As the above answer points out, this means that the relationship between the two is the square-root of 3, or 1.732.
There is no such thing as a 'phase-to-phase' voltage; the correct term is 'line-to-line' voltage. Whenever you mention a value of voltage for a three phase system, it is considered to be a line-to-line voltage unless it is stated clearly that this is phase voltage (line to neutral) voltage.(The reason that there is no such thing as a 'phase-to-phase' voltage is because phases exist between, or 'across', line conductors or between a line conductor and a neutral.) That is a world wide practice for electrical power engineers.
It depends how they are connected. If they are connected between line conductors then they are measuring line voltages. If they are connected across phases then they are measuring phase voltages.
Voltage is checked with a volt meter. It doesn't have to be 3 phase. It is used to test any potentials across phase to phase, line to neutral, line to ground or across resistances. Be careful when testing live voltages as a misplace of the meter probes could cause an arc flash that could give you three degree burns to any exposed skin.
Motor started will have overloads the contactor connect es line voltage.
In a three phase three wire system, the phase voltage and line voltage are one in the same just different terminology. In a three phase four wire system, the line voltage is higher than the line to ground voltage. Line to ground is, line voltage divided by 1.73 (square root of three). For example 480volts /1.73 = 277 volts.AnswerIt depends upon the configuration of the three-phase system. For a delta (or mesh) connected 3-wire supply system, the line voltage is exactly the same as the phase voltage. For a wye (or star) connected 4-wire supply system, the line voltage is 1.732 (the square-root of 3) times the phase voltage.By way of explanation, for both wye and delta systems, phase voltages are measured across the windings of a three-phase transformer or across individual loads, whereas line voltages are measured between lines. For a wye-connected system, phase voltages can also be measured between any line and neutral.
Mathematically, just divide 480 by the square root of three. Electrically, 480V refers to the line-to-line value of a three phase system. For example, measure the voltage across A-phase and B-phase and you'll get 480V. 277V is the line-to-neutral value. Measure the voltage across A-phase and the neutral conductor and you should get 277V.