Phase converter and wire gauge question..

[waggie]

***oops, the title should have read: Placement of the phase converter in regards to wire size***


I'm in the middle of wiring up my shop and have to make some decisions, since my Main electric panel is about 70 feet away from where my 3 phase machines are going to be.

Option A: run a 80-90 foot long, 8-3 wire carrying 230V single phase to a 5hp rotary phase converter, so the phase converter can be close to the machines, therefore the 3 phase wires are kept at a minimum.
or

Option B: Put the Phase converter right next to the panel, and run 80-90 foot long 12-3 wire carrying 3 phase power to the machinery. This option will still require 8-3, but less than 10 foot long.

I have enough 8-3 and 12-3 (actually have 6-3 and 10-3) to do this, just need to know which way is better... and why.

thanks in advance.

 

[kaffine]

Are you going to be turning the phase converter on and off frequently? I tend to turn mine off if it is going to be a while before I need it again. So I would put it close to the machines that are going to use it.

 

[Mr onetwo]

Good question.I am going to be making this decision soon and here's hoping an expert(electrical engineer) will answer this.The "why" is much more important than the "how" IMHO.

 

[Kevin54]

From my Box to Phase Converter and from my Phase Converter is all ran in #10. I was advised to run that size and I'm maybe 15' from box to PC and maybe 30' from PC to both mill and lathe

 

[Norcal]

Phase converters are covered in NEC art 455.

I. General
455.1 Scope. This article covers the installation and use of
phase converters.
455.2 Definitions.
Manufactured Phase. The manufactured or derived phase
originates at the phase converter and is not solidly connected
to either of the single-phase input conductors.
Phase Converter. An electrical device that converts singlephase
power to 3-phase electric power.
FPN: Phase converters have characteristics that modify the
starting torque and locked-rotor current of motors served,
and consideration is required in selecting a phase converter
for a specific load.
Rotary-Phase Converter. A device that consists of a rotary
transformer and capacitor panel(s) that permits the operation
of 3-phase loads from a single-phase supply.
Static-Phase Converter. A device without rotating parts,
sized for a given 3-phase load to permit operation from a
single-phase supply.
455.3 Other Articles. Phase converters shall comply with
this article and with the applicable provisions of other articles
of this Code.
455.4 Marking. Each phase converter shall be provided
with a permanent nameplate indicating the following:
(1) Manufacturer’s name
(2) Rated input and output voltages
(3) Frequency
(4) Rated single-phase input full-load amperes
(5) Rated minimum and maximum single load in kilovoltamperes
(kVA) or horsepower
(6) Maximum total load in kilovolt-amperes (kVA) or
horsepower
(7) For a rotary-phase converter, 3-phase amperes at full
load
455.5 Equipment Grounding Connection. A means for
attachment of an equipment grounding conductor termination
in accordance with 250.8 shall be provided.
455.6 Conductors.
(A) Ampacity. The ampacity of the single-phase supply
conductors shall be determined by 455.6(A)(1) or (A)(2).
FPN: Single-phase conductors sized to prevent a voltage
drop not exceeding 3 percent from the source of supply to
the phase converter may help ensure proper starting and
operation of motor loads.
(1) Variable Loads. Where the loads to be supplied are
variable, the conductor ampacity shall not be less than
125 percent of the phase converter nameplate single-phase
input full-load amperes.

(2) Fixed Loads. Where the phase converter supplies specific
fixed loads, and the conductor ampacity is less than
125 percent of the phase converter nameplate single-phase
input full-load amperes, the conductors shall have an ampacity
not less than 250 percent of the sum of the full-load,
3-phase current rating of the motors and other loads served
where the input and output voltages of the phase converter are
identical. Where the input and output voltages of the phase
converter are different, the current as determined by this section
shall be multiplied by the ratio of output to input voltage.
(B) Manufactured Phase Marking. The manufactured
phase conductors shall be identified in all accessible locations
with a distinctive marking. The marking shall be consistent
throughout the system and premises.
455.7 Overcurrent Protection. The single-phase supply
conductors and phase converter shall be protected from
overcurrent by 455.7(A) or (B). Where the required fuse or
nonadjustable circuit breaker rating or settings of adjustable
circuit breakers do not correspond to a standard rating or
setting, a higher rating or setting that does not exceed the
next higher standard rating shall be permitted.
(A) Variable Loads. Where the loads to be supplied are
variable, overcurrent protection shall be set at not more
than 125 percent of the phase converter nameplate singlephase
input full-load amperes.
(B) Fixed Loads. Where the phase converter supplies specific
fixed loads and the conductors are sized in accordance
with 455.6(A)(2), the conductors shall be protected in accordance
with their ampacity. The overcurrent protection determined
from this section shall not exceed 125 percent of the
phase converter nameplate single-phase input amperes.
455.8 Disconnecting Means. Means shall be provided to
disconnect simultaneously all ungrounded single-phase
supply conductors to the phase converter.
(A) Location. The disconnecting means shall be readily
accessible and located in sight from the phase converter.
(B) Type. The disconnecting means shall be a switch rated
in horsepower, a circuit breaker, or a molded-case switch.
Where only nonmotor loads are served, an ampere-rated
switch shall be permitted.
(C) Rating. The ampere rating of the disconnecting means
shall not be less than 115 percent of the rated maximum
single-phase input full-load amperes or, for specific fixed
loads, shall be permitted to be selected from 455.8(C)(1) or
(C)(2).
(1) Current Rated Disconnect. The disconnecting means
shall be a circuit breaker or molded-case switch with an
ampere rating not less than 250 percent of the sum of the
following:
(1) Full-load, 3-phase current ratings of the motors
(2) Other loads served
(2) Horsepower Rated Disconnect. The disconnecting
means shall be a switch with a horsepower rating. The
equivalent locked rotor current of the horsepower rating of
the switch shall not be less than 200 percent of the sum of
the following:
(1) Nonmotor loads
(2) The 3-phase, locked-rotor current of the largest motor
as determined from Table 430.251(B)
(3) The full-load current of all other 3-phase motors operating
at the same time
(D) Voltage Ratios. The calculations in 455.8(C) shall apply
directly where the input and output voltages of the
phase converter are identical. Where the input and output
voltages of the phase converter are different, the current shall
be multiplied by the ratio of the output to input voltage.
455.9 Connection of Single-Phase Loads. Where singlephase
loads are connected on the load side of a phase converter,
they shall not be connected to the manufactured phase.
455.10 Terminal Housings. A terminal housing in accordance
with the provisions of 430.12 shall be provided on a
phase converter.
II. Specific Provisions Applicable to Different Types of
Phase Converters
455.20 Disconnecting Means. The single-phase disconnecting
means for the input of a static phase converter shall
be permitted to serve as the disconnecting means for the
phase converter and a single load if the load is within sight
of the disconnecting means.
455.21 Start-Up. Power to the utilization equipment shall
not be supplied until the rotary-phase converter has been
started.
455.22 Power Interruption. Utilization equipment supplied
by a rotary-phase converter shall be controlled in such
a manner that power to the equipment will be disconnected
in the event of a power interruption.
FPN: Magnetic motor starters, magnetic contactors, and
similar devices, with manual or time delay restarting for the
load, provide restarting after power interruption.
455.23 Capacitors. Capacitors that are not an integral part
of the rotary-phase conversion system but are installed for a
motor load shall be connected to the line side of that motor
overload protective device.

This is from the 2008 NEC, been too lazy to put the 2011 on this computer.

 

[Dividing Creek]

I'm about to do this same thing. My setup up is a 1950 block dairy barn and the block milk parlor building 10 feet away next to the barn. My main panel is inside the front wall of the barn and I have run a sub panel to the milk parlor. The milk parlor building is set up as my wood working shop @ present. My primary need for 3ph is an old rockwell/delta planer from a high school. My planned setup will be a 1750 rpm 7.5hp 3ph motor with a controller panel made by WNY Supply.
http://www.wnysupply.com/index.cfm/fa/items.main/parentcat/25258/subcatid/0/id/328115
I was going to use 10 ga from the sub panel to the controller and then from the motor to 3 ph outlet. Anyone see a problem with any of this or any sage advice to offer ? Never played with 3ph before but the planer is a beast and was a smoking deal because it was 3ph.

 

[larry_g]

I've always been of the opinion that voltage caries better than amps. So keep the high amp conductors short and the lower amp ones long.

lg
no neat sig line