10 hp 230VAC reversible motor control

[bobj49f2]

I have a big problem. My son is a dairy farmer. He started his operation about two years ago. The problem I am having is with the silo unloader. The farm is run on 120/230 single phase. The silo was built before I came to the farm, more than 25 years ago so I'm guessing it's about 35 years old. They seem to always have trouble with this motor. Originally the silo had an 8hp motor but my father-in-law upgraded to the 10hp. My son just had the motor serviced and the orginal three position switch, "Forward/Off/Reverse" was toast. This is a rotary type switch. Because no one makes this kind of switch any more because of liability reasons I am forced to build a new control system to control the motor. I build and install industrial control systems so building a control system is no problem.

The real problem is the cost and time. So far I am having a problem finding a four pole reversing motor starter. I can find three poles in stock at my vendors all day on their web sites, no four poles. I have found four pole contactors which are special order and I could build a reversing motor starter but because this is a 10 hp motor and pulls 50+ amps. The single contactors are in the $400-500 range each and have a 1-2 week lead time. My kid needs the silo running ASAP. Because the unloader is down he is buying corn at $500 a load and it only lasts him a couple of days. Since we got the motor back I can rig it up directly to the circuit breaker to make it run but it is not the correct or safe way to do it. This motor is under a big load and it won't have any thermal overload protection, just the circuit breaker. It also has to reverse when the unloader clogs to loosen the load.

Anyone out there with a similiar situation with a big motor like this and what did you do? No matter what I won't have a control system built for at least a week even if I could find all the parts. He's operating this operation on a very narrow profit, actually no profit right now. Anyone know of a supplier with four pole motor contactors in stock?

 

[Stuart in MN]

Is your original switch a drum switch, like this?

They're still available from Square D.
http://products.schneider-electric....witches/type-a-and-b-reversing-drum-switches/

edit: The square D switch appears to be only rated up to 7.5hp, but you may be able to find a similar model from other manufacturers that does have the extra capacity. A 10hp single phase motor is a pretty rare beast.

 

[bobj49f2]

Thanks for your reply.

This is the type he had on the motor but it's fried. I talked to my vendors about using a switch like this and they told me they stopped selling them some years ago because of the liability associated with them. The problem is if the power is cut for any reason, circuit breaker popped or a power outage, and the switch is left in one of the on position the motor will start as soon as the power is restored. This is not a good situation if someone happens to be resting against the piece of machinery.

I talked it over with my engineer and we came up with a solution. We're going to use three 3 pole contactors. One is for the two wires that are always energized whenever the motor is started and two others for switching the pair of wires that have to be flipped to change direction. I was thinking of doing this but wasn't sure that was acceptable.

Yeah, I know the single phase motor is rare. In the industrial field we use only 3 phase motors and finding standard reversing motor starters are easy to find. Farm machinery is wired, constructed and operated a lot different than industrial equipment. We would never be able to assemble a machine without a multitude of shields, interlocks and other safety circuitry. On a farm they're have shafts spinning at 4000 rpm without covers and hardly any machine has any kind of safety circuitry, at least nothing like we have in the industrial field.

I am going to do my best to keep my kid safe. I'm building a large control panel to control all of the motors associated with the silo and food distribution. Everything is going through latching circuits so if power is dropped the motors stop and the operator has to go up to the panel and restart the motors manually. Also, emergency stop buttons in easy to get to locations.

Walking around a farm, and being use to all the safety procedures I'm used to, and seeing all the potencial dangers can be very scary.

 

[Socophreak]

Check with local HVAC shop, they should have or be able to get a 4-pole, if not you could mount a couple of 2 pole in parallel with fuses to protect if one fails. It's not ideal, but it would work. Whats the 4-pole for anyways? 120/240 should only be 3 wires w/ extra ground.

I would honestly just wire up a rocker, selector, or toggle with on/off/on positions. Wire that up to a couple of contactors rated for the load, one for FWD one for REV. One position engages FWD and the other engaged REV. The motor itself should have instructions on the plate on which wires to change to run in reverse rotation. Mount all that in a waterproof box and you've got a box that will have easily sourced parts for years to come.

Edit: I noticed your engineer is doing the same thing I recommended. I see this style of motor reversing in bakery equipment that requires reversing motors for even baking. All you really need to do is ensure that both contactors cannot be engaged at the same time for added safety.

 

[Stuart in MN]

Sounds like you have a good solution. Farms are dangerous places, all the extra controls and E-stops will make it safer for him.

 

[bobj49f2]

Check with local HVAC shop, they should have or be able to get a 4-pole, if not you could mount a couple of 2 pole in parallel with fuses to protect if one fails. It's not ideal, but it would work. Whats the 4-pole for anyways? 120/240 should only be 3 wires w/ extra ground.

I checked my vendors web sites today, no one is open today, and I was able to find 4 pole contactors but they're very pricey and there's a 1-2 week lead time. I'm kind of in a hurry for this.

You need 4 poles to keep the four wires coming out of the motor separate. L1 is always connected to T1, and L2 is always connected to T4 on the motor. You have to switch T5 and T8 back and forth between L1 and L2 to have the motor reverse.

In our design the first contact will swith L1 to T1 and L2 to T4, this contactor will be energized whenever the motor is turned on. The second one will connect L1 to T5 and L2 to T8 and will be energized when the motor is going forward. The third contactor will connect L1 to T8 and L2 To T5 when we want the motor to reverse. We'll be using three 3 pole contactors because they're cheap and a lot easier to find than the 4 pole contactors. We're also running thermal overload protection. The second and third contactors will be wired so only one can be pulled in at a time.

I've never wired a motor like this. I've wired hundreds of 3 phase and a good number of single phase but never a single phase reversible motor. The wiring diagram look different.

 

[sparky36000]

Just curious, but are three two pole contactors an option? I'm guessing three 3 poles were more readily available in that size.

 

[bobj49f2]

The 3 poles are more readily available. I'm not even sure if 2 pole is an option. We only use 3 poles in our control panel even if we're going to use one pole. Some times the spare poles used at a later date to add a circuit.

 

[Socophreak]

Correct me if I'm wrong, but I think you should be able to use two contactors.

From contactor to motor, both contactors should be wired same way.
T1 - T1
T2 - T4
T3 - T5

From the wiring block or breaker you should have
FWD
Phase 1 to L1
Phase 2 to L2
Phase 2 to L3
Rev
Phase 1 to L1
Phase 2 to L2
Phase 1 to L3
Then obviously switch/es will run to the contactor winding.

Instead of relying on 3 contactors, you rely on two. I work on a few models of equipment that use this principal to reverse rotation. Your motor could very well be different, but every 1Ph motor I've wired has been the same.

 

[bobj49f2]

I was going off a wire diagram I found on line for a reversible single phase motor. The motor is still in the. Repair shop. I'll check the motor go. verify the wiring once my son picks.it.up and brings.it.back.home. he gook it.out and didn't pay attention to the wiring. I just called into this project yesterday.

 

[sparky36000]

Socophreak is correct, you can do it with two three pole contactors. My drawing is a little crude, but hopefully you get the idea. My drawing actually reverses the run winding instead of the start winding, but as long as you change the relationship between start and run in forward and reverse, it will work fine(which I'm sure you know seeing how you build control panels). Maybe Socophreak can chime back in and see if this is how they do it on the equipment he works on.

 

[RPH]

What you should be looking for is reversing contactor . These are mechanically interlocked to keep both contactors from pulling in from failure. Without this a big bang could happen. They make 3 and 4 pole styles. The web is your friend.

 

[theoldwizard1]

I've been doing a lot of searching on the 'net and have not been able to find a 240V switch that is rated for 10HP. 10HP at 480V, yes.

The Hubbell Class 58 Drum Controller is rated as above. This PDF shows dozens of different wiring options.

 

[sparky36000]

What you should be looking for is reversing contactor . These are mechanically interlocked to keep both contactors from pulling in from failure. Without this a big bang could happen. They make 3 and 4 pole styles. The web is your friend.

I think he has been able to find those types of solutions, but if you read all his posts, time and cost are factors. Three pole contactors are readily available and can be electrically interlocked to do the job safely.

 

[RPH]

"I think he has been able to find those types of solutions, but if you read all his posts, time and cost are factors. Three pole contactors are readily available and can be electrically interlocked to do the job safely."

Electrical interlocks do fail. Reversing contactor have a solid mechanical interlock with the electrical safeties. Check the web.

 

[bobj49f2]

Ok, we got the motor back yesterday and temporally wired so my son could get the feed out to feed his cows. The unloader motor had a long SO cord attached to it so I just bypassed the bad switch. Right now it will only run in one direction.

Here's the wiring diagram inside the motor box. The bottom diagram is how I am going to have to wire it. I'll still need three separate contactors. C1 will be energized for both CCW and CW operation, C2 for CCW operation and C3 for CW operation.

View media item 28557
P1 & P2 are wires from the thermal overload switch in the box.

 

[bobj49f2]

Sparky, with your diagram you're not breaking power to T8, when de-energizing a motor you have to break all legs of power.

Socophreak, I need to connect and break wires going to P2. P1 and P2 are the thermal overload protector switch in the circuit.

One more added thing I have to factor into this whole mess is the control panel has to mount on the motor because when they do servicing of the silo unloader they use the motor to help push the unloader out of the silo. There is a 10 foot 3 conductor SO from the motor to the outlet on the wall to facilitate this. Otherwise I'd have to have a 5 conductor cord with plug and outlet, that would be very pricey and bulky. The fun never ends on a farm.

 

[sparky36000]

Sparky, with your diagram you're not breaking power to T8, when de-energizing a motor you have to break all legs of power.

No you don't. Unless your controller also serves as your disconnect.

NEC 430.84
Need Not Open All Conductors. The controller
shall not be required to open all conductors to the motor.
Exception: Where the controller serves also as a disconnecting
means, it shall open all ungrounded conductors to
the motor as provided in 430.111.

 

[bobj49f2]

Sparky,

I just wouldn't be personally comfortable with not breaking all hot leads to the motor. When I go into a system I want to make sure if it looks like all power is off it's all off. I personally don't screw with a motor unless the main disconnect is off or the motor is unplugged and I personally see the plug unplugged. I'm thinking more of others. Over the years I've found if there is a way for someone to get into trouble they will find a way to do it. I would hate so see someone pull the cover off the motor and come in contact a hot wire they thought wasn't there.

 

[sparky36000]

Very valid concerns. You said you were trying to save space and some money, I was just trying to give you ideas and still meet code minimums.

 

[Socophreak]

Fair enough. Looks like you've got it all covered and at least it will be easy to source parts for.

 

[bobj49f2]

Sparky, I appreciate that. I am doing this on a tight budget but I also need to feel safe about it. I have trimmed down the components quite a bit but when it done I'll have about $800 in a small simple box with a few external push buttons.

I've had to try to interpret the codes at times and it gives me a head ache. Some times no matter how many times I reread some it just doesn't seam logical. But do I know, I'm not a highly eductated tech geek. I just try to do my job as best as I can.

 

[hcetih]

I think no matter how you do it, if the control panel is separate, you have to run 5 wires to the control panel (bobj49f2 Senior Member) I have a disposer that is reversing. 10hp. has p1, p2, t4, t8, t5 @ the motor. The control panel is missing the wiring Diagram. There is 4 wires and a ground running to the motor. A variety of people have been messing with it. I think they are using one of the feeders for a ground. They have been using it with only forward hooked up. There is 2 3 pole contactors in the box. They only have 2 wires hooked up to the contactors, the ground is hooked up and the other 2 are taped.

 

[hcetih]

I don't think you can reverse the motor from a remote controller without running 5 wires to the motor. I have a disposer with p1 etc 10 hp. 1 ph. The controller has 2 3 pole contactors. There is 5 wires running to the motor but 1 is being used as ground, I don't think it used to be. The control panel is missing the wiring diagram it is not available. They have been using it in only forward. 2 of the wires going to the motor aren't hooked up. Many people have messed with it in 18 years. I have to figure out how to wire it correctly. New motor. Some else disconnected the old one(s).

 

[hcetih]

1 two pole contactor for disconnect, 2 3 pole contactors, L1 to motor as p1. Put L2 to top of each contactor on the 1st pole, jumper to 2cd pole. Put P2 on the top 3rd pole of each contactor. put t8 on 2cd pole of the bottom of the 1st contactor and the bottom 3rd pole of the 2cd contactor. put t5 on the 3rd pole on the bottom of the 1st contactor and the 2cd pole on the bottom of the 2cd contactor. Forward being the 1st contactor and reverse being the 2cd. This gives you a disconnect for both L1 and L2. Of course you need 5 wires from controller to motor. Draw it out. It will work.

 

[MTW]

For the record, rotary (drum) switches for almost any configuration you could dream up are available, just not from an American manufacturer.

You can download a catalog of one well known German manufacturer from here.
http://www.saelzer.com/download/documents/Saelzer_Catalogue_Rotary_Cam_Switches_NS113-GB.pdf
They do have a sales office in Arizona, and some distributors through the country.

This catalog is not easy for laymen to select from however, you really need to understand what your needs are to select the correct switch. And then provide a suitable enclosure to house it to suit your environment. These switches are custom or factory configurable from 10 to 315A

For the motor in question 10HP 230V 1 Ph = 50A FLC * 1.25 = 62.5A rated switch assembly. The function of single phase reversing would be fulfilled with a identification #61214 on page 64 & 71 of the catalog. This particular model has 3 stages with 5 contacts to get the function you'll need Then you select the amperage according to your needs. The models offered near this size is 63 or 80A, 80A model would be the one to use in this case.

I use these switches on large 3 phase food mixers that are 10HP 3PH 2SPD Reversible, as this is what the machines were designed to use from the OEM.

For the latching and overload function you could use a standard starter in your panel, and still retain the simplicity of the manual switch installed right at the motor.