3 Phase ?'s

Status
Not open for further replies.
M

maxboosteric

Member
Hi guys,

I'm hooking up a conveyor tomorrow at work and it has a Leeson 1/2 hp 208/230 motor on it. I also ordered a ac control to slow the speed down on the conveyor. I have 3 legs coming in that have 120v 120v and 240v. Is this called low voltage 3 phase 208v? I'm alittle confused on the 3 phase stuff. I thought 3 phase had 240v on all legs. I trying to figure out if I have the right voltage there already or if I need to run 240v 240v 240v over to the conveyor to run the Leeson motor. Sorry for the low knowledge I'm still learning and trying to be careful about it.
Thanks Eric
 
Re: 3 Phase ?'s

What are your measurement references?

On a 3? 208Y/120 system you will have 120V to ground on all three legs and 208V between ay two phases. On a 3? 480Y/277 system you will have 227V to ground on all three legs and 480V between any teo phases.

On a 3? 120/240 Delta system, you will have two legs at 120V to ground and the third at 208V to ground. There will be 240V between any two phases.

I am not aware of any systems with 240V to ground.
 
Re: 3 Phase ?'s

the cost of a new 3 phase motor will be about the same as having an electrician hook it up--conveyor equipment isn't cheap!!!
 
Re: 3 Phase ?'s

I am the "electrican", go figure huh.

My measurements are from ground.
120v 120v 208v(unsure on 208v)

I will double check tomorrow though. Does a ac motor care if its hooked up in Y or delta or will either work.
Eric

[ March 13, 2005, 09:10 PM: Message edited by: maxboosteric ]
 
Re: 3 Phase ?'s

Does a ac motor care if its hooked up in Y or delta
Click to expand...
It sure does.

Some three phase motors are designed to be connected wye and others delta. You can't change it in the field anyway, unless it has 6 or 12 leads.

How many leads does it have?

Ed
 
Re: 3 Phase ?'s

The motor windings care if they are connected delta or wye. The motor does not care if the power source is delta or wye, it only needs the three phase conductors.

Note, when taking/reporting voltage readings always remember the phase to phase as well as phase to ground (and/or neutral).
 
Re: 3 Phase ?'s

The 9-lead motor's winding connection cannot be changed from wye to delta, it is connected internally by the manufacturer.
You can't tell whether it is wye or delta wound by looking at the lead numbers, as the terminal identification is the same for both.

If there is no connection diagram on the motor nameplate, a few minutes with an ohmmeter will determine whether it is wye-wound or delta-wound.

Motor3.gif


Ed
 
Re: 3 Phase ?'s

As Jim has explained, it doesn't matter to the motor which way the supply is connected, as long as the voltage is correct for the motor.

However, the motor windings must be connected the way they were designed to be connected.
There should be a diagram on the motor that you can follow to get windings connected for the available voltage.

If there is no diagram, you will have to determine whwther the motor is wye-wound or delta-wound, and then select the appropriate connection from the four below.

Ed

MotCon11.gif
 
Re: 3 Phase ?'s

I remember the motor plate, its the same as your parallel- wye (low voltage)

I'm still not sure on if I have the right voltage in the area yet. I'll get the readings tomorrow.
Eric
 
Re: 3 Phase ?'s

I checked power from ground and got 120v 208v 120v
power from phase to phase was 240v. So I should be able to use the power that is already there to run my Leeson motor along with the AC drive, right?
Eric
 
Re: 3 Phase ?'s

Yes you have 240 V 3 phase power for your motor. Size overloads for the amps which correspond to the 230 V listing on the motor. Check rotation before starting conveyer if it will be damaged by going backwards. Maybe remove a belt or something if you don't use an instrument to check phase sequence.

Jim
 
Re: 3 Phase ?'s

If it is a 3phase motor you can not go by what you are reading to ground, rather have to take in account the collective voltage.

When checking rotation also remember that the shaft side of the motor is actually the "back of the motor". The other side is the front of the motor and should be running in the counter clockwise rotation for correct operation.

[ March 22, 2005, 10:10 PM: Message edited by: bigjohn67 ]
 
Status
Not open for further replies.
Top