How do i wire up a 3 hp three pahse motor ???

[beginner_351]

3 pahse delta

OK , im new to all this , just retied from working due to health issues so have a lot of spare time to killl am board shitless at home

I am so to speaking DIY-studying , so guys if i ask stupid questions don't shoot me.
I know electricity is extremely dangerous , so i'm extremely careful when tinkering with power supplies or any electrical appliances.

I am making a log splitter as my back is not that strong in cutting up logs for my fire place.

I have made a device that uses a hydraulic jack to drive the axe into the log and spilt it.

now im getting a lift more adventurous and coupling a 3 phase motor to pump up the jack for me .

I am confused with all this L1 , L2 , L3 , L4 wiring on the 3hp three phase motor.
so need some help if anyone know the way to wire it up.

any help would be appreciated , i know i should just call a electrician but i want to learn myself and once i have been shown i can grasp the concept very quickly

cheers guys

 

[brevor]

wire motor what is l1 l2

Im assuming you have 3 phase power available at your home.
It's simply a matter of connecting the 3 "L" wires one wire to each phase
of your line.
If after doing this if the motor runs in the wrong direction simply
reverse any 2 of the wires.

L4 ?? I dont know what that is, 3 phases should be L1, L2 & L3.
If you have an L4 you need to get the motor data and look it up.

Bruce

 

[miGs]

usa 3hp grounded

I agree, please look at your motor manual.

I am assuming L1, L2, L3 are for line conductors...L4 for grounding.

But I am not sure, as grounding is normally designated as "N".

So its best to consult your motor manual.

 

[beginner_351]

3 pahse motor connections

hi

sorry guys , you are right , one too many L's

L1, L2, L3, N

there are 4 wires in total

if there are no indication ( Labellings ) of what L is from the other is there a standard colour code in wire to match each individual L1 L2 L3 and N ?

And can i use a multimeter to determine the connections ?

Can one make differant connections to make the motor operate differantly

what does a H-bridge connection do and its purpose ?

cheers

 

[brevor]

Yes use a multimeter, check where the N wire is going. It should either connect to the L1,L2,L3 group or it will connect to the motor case. This will determine how you need to connect the motor. Is there a plate on the motor that shows the operating voltage?
An H bridge is generally used for DC motors.

Good Luck.

 

[echo47]

This may be helpful:
https://en.wikipedia.org/wiki/Three-phase_electric_power
https://www.allaboutcircuits.com/vol_2/chpt_10/5.html

Many three-phase connections use five wires: L1, L2, L3, N (neutral), and ground.
Some use only four wires: L1, L2, L3, and a shared neutral-ground.

If you randomly mix-up the L1-L2-L3 phases, the motor will probably spin fine, but there's a 50% chance that it will spin backwards. The pump mechanism may not like that.

Happy logging!

 

[vsgiri]

Beginner_351,

What's the hp of your 3-ph motor?
If it's more than 1 hp you need to consider start-delta motor starters.
Take a look at this:
**broken link removed**

Good luck,
Giri

 

[beginner_351]

hi Guys

thanks for the replies and some reat information i have read and somei understood

is there any information on how to control the speed of the motor in here a cheap method

its a 7.5kw AC redcution motor

cheers

 

[brevor]

Beginner_351 said

"is there any information on how to control the speed of the motor in here a cheap method"

No, 3 Phase controls are expensive.

 

[House_Cat]

The speed of a 3 phase induction motor is determined by the frequency of the line current and the windings in the motor.

The only way to vary the speed is with a solid state or rotating frequency converter - neither of these methods is cheap or easy.

If you want to see what a solid state converter looks like, there are schematics at:
https://www.logosfoundation.org/kursus/2113.html

If you need a variable speed motor, you would be better off with a DC motor or a single phase universal motor. A DC motor would be preferred for high torque loads, and the universal AC for lower torques.

 

[lkraemer]

If you are wiring up a Three Phase 230 Volt motor the wiring is different than for a
460 Volt Motor.

REF:
**broken link removed**

You MUST provide some protection, Fuses, Overloads, and such to have the proper
protection.....else the fire/sparks can fly, and you don't want that. This means you will
need a Motor Starter that contains Overloads and Fuses.

The three fuses should be sized to protect the wiring, and the Overloads should be
sized according to the motors service factor rating. If I remember correctly, for
Service factors > 1.00 you can size the overload for 120%. Otherwise the Overload
should be sized such that it is as close to the Nameplate current rating, but not over,
according the the overload charts. Starting current (6 times Lock Rotor) can be very
high, up to six times Lock Rotor so everything must be properly sized.

lk

 

[threephase]

The motor rated at 7.5kW equates to about 10 horsepower in old money. That size of motor needs a starter. This is a type of relay that incorporates an over-current trip. The type of starter I am familiar with generally has a start and stop button incorporated. You can wire external start/stop switches as well. For an application that includes danger (powered log cutting sound dangerous to me) it would probably be a good idea to rig up a foot switch as an emergency stop.

The supply ought to be via a fused isolator with HRC fuses. These allow for high starting currents.

There are three windings in the motor. Ends of each winding are usually brought out to a terminal block. There may be links on this block to configure the motor as "star" or "delta". Suitability to connect as star or delta depends on the voltage rating of the windings (see the motor rating plate).

The star arrangement has one end of each winding connected together (the star point) and the other ends go to L1/L2/L3. Whilst the star point is effectively neutral, it does not need to be connected to the supply neutral.

In delta, the three windings are connected in a triangle. The supply phases are connected to the three corners of the triangle. This means that each supply phase is connected to two windings. Each winding has around 400V across it in UK (that's 230V times sq root 3). For US,it would be about 190V for a nominal 110V supply. There is no neutral point or connection. The delta arrangement gives more power but usually require a motor to be started in star first. A star/delta starter switches over from star to delta after a time delay.

In UK, colours used for the phases to be red/yellow/blue with black for neutral. Modern EU compliant colours are brown/black/grey for the phases with blue for neutral. In all cases earth is green/yellow.

Rotation speed is usually a bit lower than the theoretical maximum (3000rpm for 50Hz supply, 3600rpm for 60Hz) because there are some losses. See motor rating plate. Speed controllers are expensive because they have to create variable supply frequency at high currents. That involves high power triacs or similar and lots of control circuitry. However, they work well and can usually be configured to give "soft start", which is desirable in some applications.

3phase