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Calculate inrush for 3-phase motor
''Industrial control circuits and motor control loads typically require more current when they are initially energized than under normal operating conditions.
This period of high current demand, referred to as inrush, may be as great as ten times the current required under steady state (normal) operating conditions, and can last up to 40 milliseconds.  A transformer in a circuit subject to inrush will typically attempt to provide the load with the required current during the inrush period.''
Inrush calculation
Locked rotor calculationInrush is the amp consumption of a motor during start-up.

Motors are inductive. Inductive loads consume more amps when starting. Once the motor has started, the amperage drops to normal.

Each motor has a label with a locked-rotor code that is needed for the calculation. Use chart below.

The locked rotor code is a letter A-V, with each letter corresponding to a range of KVA per HP (horsepower).
KVA is kilo volt amps. Volt amps is watts. So KVA is a measure of watts or power or KW ... how much power the motor delivers.
The locked rotor code is used to calculate the inrush or amperage needed for that specific motor during start up.

The example problem on left shows 50 HP 3-phase motor with locked-rotor H, which has KVA range of 6.3-7.1 KVA per HP.
The KVA range is plugged into the formula:
7.1 x 50 HP = 355 KWA or KW at start up
355 KW = 355,000 watts
P (power or watts) = E (volts) x I (amperage) x .173
1.73 is the square root of 3, used for 3-phase calculations.
355,000 watts = 480 volts x I (unknown amps) x 1.73.
Solve for amps: I = 355,000 ÷ 480 x 1.73

locked rotor chart
Residential single-phase motors also have inrush. This is generally not an issue when calculating household wire and breaker size since the HP rating is relatively small, start-up is brief, and circuit breaker doesn't react fast enough to trip with the small surge of amperage (heat) on the wire. However large swimming pool motors, and other application that use 3-5 HP motors should have oversized wire and breaker to supply ample electricity for start.

Resources:
Locked rotor KVA nameplate rating: Calculate inrush .pdf
Difference between single-phase and 3-phase
Color code for wire
"Industrial and commercial 3-phase electric systems differ from residential single-phase: 3-phase power is more complex, but more efficient in motor applications, and large area uses. Higher voltages of 277/480v and 347/600v distribution systems are more efficient, but considerably more dangerous, and should only be maintained and modified by trained and qualified electricians."
"In a balanced 3-phase system, the wires can be about 75% the size of conductors (wires) for a single-phase two-wire system of the same KVA (power) rating. This helps offset cost of supplying the third wire required by 3-phase systems."
Voltage reaches 0 on each individual line, but at no time does voltage reach 0V on all 3 lines at same time. This translates to higher average voltage per rotation of generator for 3-phase compared with single-phase. When 3-phase is connected to a motor, the average higher voltage means less amperage is needed, which means motor runs cooler. Amperage is the heat on the wire that trips a circuit breaker. Volts x amps = power (watts), so 3-phase can deliver more power with less heat loss, making 3-phase more efficient than single-phase. Lower amps also means that wires can be smaller, thus lowering cost of installation.
"The horsepower rating of three-phase motors is about 150% greater than for single-phase motors with a similar frame size. The power delivered by a single-phase system pulsates, and the power falls to zero three times during each cycle. The power delivered by a three-phase circuit pulsates also, but it never falls to zero. In a three-phase system, the power delivered to the load is the same at any instant. This produces superior operating characteristics for three-phase motors."
Resources:
3-phase circuits and basic math .pdf
Difference between single-phase and 3-phase
Transformers and inrush
''Industrial control circuits and motor control loads typically require more current when they are initially energized than under normal operating conditions.
This period of high current demand, referred to as inrush, may be as great as ten times the current required under steady state (normal) operating conditions, and can last up to 40 milliseconds.
A transformer in a circuit that is subject to inrush will typically attempt to provide the load with required current during the inrush period. However, it will be at the expense of the secondary voltage stability by allowing the voltage to the load to decrease as the current increases.
This period of secondary voltage instability, resulting from increased current, can be of such magnitude that the transformer is unable to supply sufficient voltage to energize the load.
The transformer must therefore be designed and constructed to accommodate the high inrush current, while maintaining secondary voltage stability.
According to NEMA standards, the secondary voltage would typically be at 85% of the rated voltage.''
Amp load by kW
Single-phase/ 3-phase Amp load by Kilowatt


Larger image
Breaker size / kW chart
Single-phase/ 3-phase Wire and Breaker size chart


3-phase wire size
Larger image
Distance from power company transformer affects operation of 3-phase motor.
Longer distance requires larger gauge wire to supply enough amperage.
Motor resources


amp draw for motor
Volts x Amps = Watts
Amps = Watts divided by Volts


Typical motor starting currents of 6 to 8 times normal running current when starting.
Motor amp draw

motor
Buy:
AO smith / Century / motors
Dayton motors
Electric motors
Draft inducer blowers for gas appliance + water heater
Water pumps
Wet dry vacs

Resources:
Motors can run 10% more or 10% less than rated voltage
AO Smith motors with troubleshoot and wiring .pdf
AO Smith motor wiring
Magnetic motors is AO Smith, AO Smith motors are now Century
Motor troubleshooting/ pdf
Motor troubleshoot 2/ pdf
Timer for 2-speed motor
Repair and wire motors .pdf
Basic motor wiring illustration .jpg
Reverse motor .pdf
Hayward pool equipment error codes
Swimming pool replacement motors and identification
The motor doctor
Dayton motor guide/ pdf
Control motor with 2 switches
Wattage consumption of motor .pdf
Always connect ground wire.
More than 3300 feet above sea level, use next higher horsepower.
Motor must be grounded. Test that ground is connected. Turn power off before touching motor.
Incorrect voltage at motor will cause motor to overheat. Check wire size.
Motors are hot to touch. Provide ample circulation around motor.
" Current capacity must be adequate enough to maintain rated voltage at the motor terminals under all conditions. If it’s too high, contact the local utility.
If it’s too low check for overloaded circuits, loose connections or wire of the wrong gauge"

Horsepower / wire size / distance
Motor horsepower and wire size for 115Volt and 240V
Horsepower = watts ÷ 746
Resource:
How to wire subpanel

For example: 1-1⁄2 Hp motor at 115 volts over a distance of 150 feet, use #8 wire.
If the motor can be installed to operate on 230 volts, #12 wire should be sufficient for a 150 foot distance

Horsepower / wire size / distance

Larger image
Use larger wire and breaker with longer distance
Length of wire/ amp draw chart

Water heater wire size chart
Larger image
Water heater Circuit Breaker size/
non-simultaneous

Ordinary residential water heaters are non-simultaneous. Tank label will show type of operation.
Longer distance, use larger wire and breaker
Oversizing wire and breaker will lower heat loss and improve efficiency
Cooler wires = cooler circuit breaker = longer life for breakers and main panel
Resource:
How electric water heaters work


Dual-element water heaters are 240Volt and are normally factory-wired for non-simultaneous.
This means only one element is ON at a time.
Both elements are never ON at same time.
Resources:
How to wire water heater elements and thermostats
How to wire tankless electric water heater
Single-phase water heater amp draw
Larger image
Water heater  Amp draw/
non-simultaneous

Ordinary residential water heaters are non-simultaneous
Same as chart above except showing actual amp draw instead of recommended breaker size
Simultaneous water heater wiring
Larger image
.pdf file
Water heater  Amp draw/
simultaneous

Residential water heater, or commercial water heater can be wired for simultaneous operation.
Some regions require commercial food sellers to have manufacturer-certified commercial-grade simultaneous water heater
Simultaneous is NOT typical for ordinary residential water heaters, except special order, or some models with 80 gallon capacity. Tank label will show type of operation.
Chart shows typical residential single-phase 120Volt, and 240Volt.
Chart also shows voltages found with commercial 3-phase service.
Water heaters can be wired for 3-phase
Resource:
How to wire water heater for simultaneous operation
How to wire 3-phase water heater
30 amp switches
Cooper 30 Amp switch
Single-pole/ 2-pole on-off switches
Buy:
30 amp 2-pole switch
30 amp industrial grade
Leviton 3033 switch
30 amp 3-way switch
30 amp Motor start switch

Heavy duty double-pole switches to turn off both hot wires in 240 volt circuit
Buy 2 pole:
30 amp motor switch
40 amp motor switch
Buy:
3-pole 40 amp switch
30 amp DPDT
Double pole double throw 30 amp switch
Buy:
30 amp DPDT switch
30 amp double pole switch
Resource:
Use this switch to toggle water heater between 120-240 volt
motor control horsepower Buy:
Motor switch
MS302 30 amp 2-pole switch
MS402 40 amp 2-pole switch

MS303 30 amp 3-pole switch
MS403 40 amp 3-pole switch
3-pole motor starter




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Tekton automotive

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