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loves80z
10-31-2005, 02:16 PM
I am taking an old (1945) AC unit apart to turn it into a rotary phase(1 to 3 phase) converter and exhaust hood. I am trying to figure out what I need to do to start the motors. It had a thermostat at one time. Can I use a light switch or something simple. The top box is the breaker and slow blow fuses. What are the other 3 boxes?

Kevin

Al_The_Man
10-31-2005, 03:54 PM
Looks like some kind of contactor with either a time delay or overload, what does the square D units have on them? If it was a AC unit it might have been a start time delay.
Al.

loves80z
10-31-2005, 05:49 PM
I am taking it apart now. I will scan the tags and post them tomarrow.

loves80z
11-01-2005, 10:18 AM
Here are some scans. I've been reading these for a few weeks and don't understand how to make it work or exactly what it is I'm seeing here.

loves80z
11-01-2005, 10:28 AM
close up pics
The yellow blue and red come from somewhere in the building (Thermostst?)

Al_The_Man
11-01-2005, 10:33 AM
You should be able to use the contactor, depends what size motor you are using, it looks like it has a 220v coil so you should not need a control transformer, I made mine this way, there are some previous posts and links I have posted, a search of the forum should get them.
You will need a couple of good quality pushbuttons rated at 250v, as well as the necessary capacitors.
Al.

loves80z
11-01-2005, 11:44 AM
Thanks Al,

I searched the posts and downloaded the jpg's from Metalworking.com. Part of what I don't understand is Do I need a start capacitor. I didn't see one on the machine. I think I can blindly hook this thing up the way they had it, but I don't understand it. I have a hard time moving forward when there is something I don't understand. The motor is 7hp and the boxes were all connected to the 7hp and a 1hp motor.

I will do reasurch on contactors and see if square D has any info specifically on these and bump when I am done.

Kevin

Al_The_Man
11-01-2005, 12:22 PM
The contactor is size 0, which according to code is good for 3hp on 230v. You should by rights be using a size 1.
You need a start capacitor if you want pushbutton start, this should be motor start grade, intermediate use, as opposed to the run caps, which should be continuous rated.
Others have used a crude way of starting by pony motor or rope pull start to get the rotor turning initially.
The P.B. start is more convenient.
Al.

HillBilly
11-01-2005, 02:03 PM
They were probably using a single phase 1hp motor as a pony motor to get the three phase motor turning. Once the motor was spinning they would apply single phase power to the spinning three phase motor ( A three phase motor will run on single phase after start up.). This arrangement does not use a start capacitor and run capacitors are optional.

Darek

loves80z
11-01-2005, 03:45 PM
I think I am starting to understand what I have.

Here's what I'm gathering. I think they were starting with no cap. I will want one so I get less surge. I should use the larger contactor or for the 7hp motor. It has thermal overload. Bonus. I should use a mamentary push button 220 rated to jump start.

I will draw a schematic of what they had and a schematic of what I think I need and repost.

Thanks
Kevin

Al_The_Man
11-01-2005, 04:48 PM
Here is my schematic if it helps.
Al.

loves80z
11-01-2005, 05:28 PM
It's starting to come clearer. I see how the startup and E-stop work. I think I want to do what U have in your schematic. I've seen things like that but now I am begining to understand. Only one question. Is 1CR and MC1 the same as the contactor for the large motor, or do I need a seperate device for MC1 (the contactor I have) and 1CR?

Al_The_Man
11-01-2005, 05:40 PM
ICR is only picked up momentarily for the start operation MC1 is the main three ph contactor. 1CR is just any small control relay with a 220vac coil. You also need an auxiliary retaining contact on MC1.
The start PB only needs to be held for less than a second otherwise you may trip the O.L.
BTW Looking at the schematic again, it is a bit misleading as I have a corrected version, 1M,MC1 & MCR are one and the same, 1CR is separate.
Al.

Al.

loves80z
11-01-2005, 05:57 PM
Does 1CR have 2 seperate contacts? One from 12 to l3 thru cap and one to MC1.

Kevin

Thanks for the help.

Al_The_Man
11-01-2005, 06:05 PM
Does 1CR have 2 seperate contacts? One from 12 to l3 thru cap and one to MC1.



Yes, it operates the start cap momentarily and initializes the pick up of MC1.
Al.

loves80z
11-02-2005, 07:51 AM
I made a diagram last night. Here it is. Can I do it like this? The one momentary button turns on both the startup coil and the motor contactor. I want to add the light across the motor contactor relay. BTW I'll be running a 1hp mill off this.

Kevin

Al_The_Man
11-02-2005, 05:13 PM
It looks Ok to me, mine is a 7.5hp unit btw.
Al.

loves80z
11-02-2005, 05:23 PM
Thanks a lot Al

U da Man!

Kevin