# 1hp 3ph 208v motor install



## micromind (Aug 11, 2007)

If you're using a phase converter, it must be running before the motor is started. 

You'll need a 2 pole contactor ahead of the phase converter and a 3 pole one between the converter and the motor although a 2 pole will work and be code compliant, it's not a good practice. 

For a 1HP motor, just about any disconnect will work. 

Another way to operate a small 3Ø motor from a single phase source is by using a VFD that will accept single phase input. Most small ones will, some are specifically designed for it.

Rob.


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## frenchelectrican (Mar 15, 2007)

I agree with Micromind.,

but just becarefull with three phase side of the rotary side due L3 typically is manufacted phase and the line to neutral voltage is not the best number to mess around ( typically anywhere from 190 to 208 volts ) so if you have any control or load that required 120 volts line to neutral be extra carefull with connection.


The other heads up with VSD with single phase input .,, becarefull with HP rating some models will have to derated but some small one can take full HP rating so check the specs if you ever go that route.

The small VSD cost been going down steady and there is some case it cheaper to buy a VSD vs the phase converter.


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## mikeDimZ (Nov 6, 2017)

Wouldn't the disconnect act as the first 2 pole contractor? I don't understand why I would need a disconnect, a 2 pole contactor, and then a 3 pole contactor? And by phase converter I meant using a couple capacitors in series to generate a 3rd leg. I was going to use a 24v control voltage as well.


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## telsa (May 22, 2015)

Seriously,

An apprentice needs to run this by his foreman// j-man.

There are so MANY ways to get this screwed up.

You'll thank me later.


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## mikeDimZ (Nov 6, 2017)

But I'm planning on doing this in my garage at some point.


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## Southeast Power (Jan 18, 2009)

telsa said:


> Seriously,
> 
> An apprentice needs to run this by his foreman// j-man.
> 
> ...


Interesting comment from someone that picked the user name Tesla.


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## Southeast Power (Jan 18, 2009)

mikeDimZ said:


> But I'm planning on doing this in my garage at some point.


Don't ever be afraid to ask questions and dabble with some experiments.
No doubt someone here could come up with a drive before Christmas.


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## mikeDimZ (Nov 6, 2017)

I can use a transformer before the contactor to step down the voltage can't I? I wasnt planning on using the manufacturers leg as a control voltage. Please explain further


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## frenchelectrican (Mar 15, 2007)

mikeDimZ said:


> Wouldn't the disconnect act as the first 2 pole contractor? I don't understand why I would need a disconnect, a 2 pole contactor, and then a 3 pole contactor? And by phase converter I meant using a couple capacitors in series to generate a 3rd leg. I was going to use a 24v control voltage as well.


It is alot safer to use the real disconnect switch on line side before two pole contractor.

the reason why use 3 pole contractor due if got overload or phase loss ( only if you have electronic O/L in there ) that will prevent any damage to your equiment.

Senice you say that you are a apprentice I really recomened that you get your favor journeyperson or look up the motor book about the RPC ( rotary phase converter ) they will help you to understand the system is. 

If you understand the basic of motor control system then it is not super hard to figure out how to get this working.


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## Southeast Power (Jan 18, 2009)

mikeDimZ said:


> I can use a transformer before the contactor to step down the voltage can't I? I wasnt planning on using the manufacturers leg as a control voltage. Please explain further


If you are practicing controls, you really don't need to go through the complications of running a three phase motor on a single phase service.
That is a completely different experiment.


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## frenchelectrican (Mar 15, 2007)

mikeDimZ said:


> I can use a transformer before the contactor to step down the voltage can't I? I wasnt planning on using the manufacturers leg as a control voltage. Please explain further


yes you can use the control transfomer before the two pole contractor that is common to do that.

however if you have some machine that do have three phase source and it come with control transfomer or any 120 volts load in there you have to take a extra step is double check the phase conductor to make sure you got the correct phase for line to neutral loads ( very common on 4 wire delta connection system ) 

The reason why if you hook up the phase conductor wrong on control transfomer you will make smoke machine right there quick.,,


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## mikeDimZ (Nov 6, 2017)

Alright then one thing at a time. Thanks for the info


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## micromind (Aug 11, 2007)

If you're using capacitors and not another motor for phase conversion then you don't need any contactor between the motor and capacitors. Just a simple 2 pole will do. The motor and capacitors are treated as one unit. 

The capacitors need to be connected to one leg of the 240 single phase and one of the motor leads. This connection is permanent......well, wire nutted anyway......lol. 

This is actually called a static phase converter. 

The main advantage is that it's simple.

The disadvantage is that the motor will produce about 1/2 of its rated HP.


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## paulengr (Oct 8, 2017)

Contactors upstream of VFD's/phase converters are a bad idea. The precharge circuits can only be energized infrequently so they burn out if you are using a contactor to start/stop. I'm not telling you it won't work. I'm telling you how to keep from destroying equipment you might have paid money for. I'm a factory certified drives technician. My labor rate per hour is almost more than the microdrive is. Not that my paycheck is that big, just what my company charges. You CAN wire it up that way and even if the drive has one of those protection features where if it powers up with a run command it ignores it until you cycle the run command (to prevent uncontrolled/surprise starting...it's an NFPA 79 thing), it's just not good practice.

Come to think of it, better just wire it up that way. I get more call outs from people that don't bypass the contactor when they retrofit a VFD onto a across-the-line starting system than you would believe. And since most drives are so heavily integrated these days, I get to sell them a new drive. So please go ahead and put in those contactors so us drives guys can make a little extra money telling you what not to do in person. Your drives manual by the way has all kinds of warnings telling you not to do this so it won't be a warranty replacement either.

You can use a contactor on the load side is but there are two problems. The first one is that if the drive is running it is looking for motor feedback. It will trip a fault (loss of phase) if you have the contactor open when you tell the drive to run. This can be disabled but why do that...the right way to run a motor from a drive is hardwired directly to the drive. Best way to start/stop is use the run or start/stop input on the device. This also gives you a chance to measure the leakage voltage through the drive transistors which is usually under 50 V and milliamps of current just to prove to yourself that its a semiconductor and not a contactor. The second reason not to do this is that it's just an extra thing to fail and serves no purpose.

You can use a contactor ahead of a drive as long as you only energize infrequently...not a good idea for a test bench setup. Plenty of people will tell you that this is OK. I work on drives all the time so my opinion is based on what I have to repair, not what you can wire up and it will work OK for a little while, like the earlier recommendation to put a contactor downstream of a drive or break only 2 of the 3 legs just because the motor can't run with only a single phase energized...it's true but not good practice especially for an apprentice trying to do things right the first time.

There is by the way one exception to the above and that's a bypass contactor system which is popular (though actually decreases reliability) in water plants and some HVAC systems. In that system the typical design uses a bypass contactor controller that intercepts and controls the signals going to the VFD. There are 3 contactors. The first one is an input contactor supplying power to the VFD. The second one is an ordinary across-the-line starter that operates in bypass (VFD is dead) mode. The third contactor operates on the output of the VFD so with two of the contactors open the VFD is essentially open circuited. The VFD and bypass contactor normally share a disconnect although there might be a separate disconnect on the VFD itself so it can be replaced while the bypass contactor is running. Finally the VFD itself often has overload capabilities so there can be an overload relay just on the bypass contactor/starter or it might be located right at the motor leads so that it provides overload protection for the bypass contactor and backup protection in case the VFD overload protection doesn't work. The control signals come from the bypass contactor controller over to the VFD and either loop through the auxiliary contacts of all 3 contactors or else use a timer or a small PLC/smart relay to prevent the VFD from starting until the contactors have all closed in and delaying long enough to allow for booting up and/or precharging.

A lockable disconnect (all legs) is required as per OSHA. Has to be able to manually lock out ALL power phases by physically disconnecting the power phases and it must be a mechanical block. So you can't for instance use a contactor and simply disconnect control voltage. 20 years ago sure there were lockable gadgets that basically held in a stop button. Those were illegal then and still are today despite massive advances in machine safety designs. It must be a circuit breaker, a disconnect, or for instance as with many HVAC's, pulling the fuses out and locking the fuse bucket. For a single phase system you can get IEC manual motor starters or the HVAC fuse option. Both are inexpensive and work well but just throwing a miniature panel breaker is even cheaper and although the locks are a joke if you had to follow OSHA you can put one of those plastic gentleman's agreement "locks" over the lever. By gentleman's agreement I mean they don't mechanically stop anything. Again you CAN intercept only 1 or 2 phase legs in a 3 phase system and this would prevent it from running but electrically it's not dead so although the mechanic is safe, the electrician isn't. Since you said apprentice, think about the consequences here for a minute. And yes on a single phase circuit with a neutral the neutral doesn't need to be locked out, as long as it's really a neutral. One 3 phase power you can have a single grounded phase leg so it wouldn't need to be disconnected and locked out but all it takes is for the apprentice to not tie one of the phase legs to ground on a delta wound transformer or put in a wye transformer or for the ground connection to corrode and rot out, and all of a sudden that leg is hot. Not that this ever happens and that I've had to troubleshoot it more times than I can remember.

Only thing you didn't mention is somewhere in there you need an overload relay whether it's built into the drive (VFD) or into the disconnect (as in a manual motor disconnect) or standalone depends on what you have. This is Code and OSHA required. A VFD can serve as overload protection, a circuit breaker cannot...EXCEPT that manual motor starters which are really a combination of an MCP (motor circuit protector....a circuit breaker with only instantaneous protection) and an overload relay are legal and give both types of protection. The problem with breakers/fuses is that they are too fast. A specialized slow-to-react device (the overload relay) is needed while the normal circuit protection devices (breakers, fuses) also need to protect against short circuits but will trip on motor inrush if you have the normal long term settings (thermal protection) in use.

However with drives, you don't generally use MCP's or time delay fuses. You use fast fuses and circuit breakers. The why is simple. A VFD uses semiconductors to switch power. These are not quite conductors and not quite insulators either. The semiconductor by nature needs to be very thin and light to do it's job without overheating. So unlike say busbars or even wire in the event of a short circuit, the semiconductors have very little thermal mass so they heat up and fail VERY quickly. So the proper circuit protection needs to be very fast with them...fuses are preferred. In fact many call for semiconductor fuses which trip in about 1-2 milliseconds or about 1/16th to 1/8th of a cycle whereas your typical "fast" fuse is 1/4 cycle.

1 HP VFD's can even convert 115 V single phase to 230 three phase. Automation Direct has a 240/230 one for $134. For a little more we distribute one that is 115 V input/230 V 3 phase output. If you want 60 Hz output just use V/Hz mode and set it to 60 Hz as the output frequency. Both phase converters (except old MG sets) and VFD's are not true sine wave outputs but generate a square wave looking output that works about the same in a motor. Just be careful of line length and make sure you bond the motor case to the VFD case, and please use the signal inputs and don't just use the line to start/stop or you will burn up the precharge circuit especially on small/cheap ones but also on very large ones that for some reason cheap out on this part.

An MG set by the way is what it sounds like. You couple a motor such as a single phase capacitor start/run motor to a generator such as an automotive alternator with the diodes removed. This gives you a three phase generator. Very primitive but back in the day before electronics this is really how we got it done or we used a DC generator with DC excitation which was easier to control and could run on a low power DC SCR drive to drive armature amps on a bigger DC motor for variable speed/torque. This is called a Ward Leonard loop. Still find one once in a while. One NC state owned building has this in their elevator and large mining excavators still use it in many of them. If the driving motor is synchronous, the VAR's you develop can cancel the crappy power factor that is inherent in DC drives.

I've even got a couple old VS series Baldors in the office that I have as emergency spares and you can buy them on EBay as well but I've had about a 50% success rate with Ebay purchased drives. New from me would be Teco or Square D. Since ABB bought them Baldor has been a pain in the rear to deal with.

Do yourself a favor if you're an apprentice. Read article 430 in NEC. Although way too many lawyers and insurance companies are involved in NEC, it's still legible and even has a couple diagrams laying everything in the motor circuit out. You can't download but you can read the entire NEC current edition 100% for free right on NFPA's web site (www.nfpa.org) and you can screen print copy/paste if you need to. It is called NFPA 70 on there. Registration is free. They just want to send you a post card ad quarterly.

And since you haven't got much drive experience, a final word of warning. If you buy a drive, it comes with a manual. The manual will be something like 40 pages or less. But be warned that this isn't the actual manual. I can't tell you how many callouts I've gotten from apprentices that tried to wire up and program their first drive with the little fake manual and then gave up in desperation. The real manual will be around 100+ pages and in the case of Allen Bradley probably almost 1,000 pages long. The little one that comes with it is an "installation manual". It is meant for electricians to be able to wire up the drive but has a lot of warnings and details that usually get ignored (and make me lots and lots of money on troubleshooting calls!) But as far as programming, this one is garbage. The big manual gives you everything else you need to know and often you don't even need the little one. But since the manufacturer can save about $5-10 in printing costs by not supplying it, all the drive manufacturers stopped including the real manuals in the box. Now you have to download it off the internet or pay separately for it. I work on all drive models so my truck would need a separate shelving unit just for all the manuals so I just keep them archived on my phone.

Sorry if I sound like I'm just looking to turn a buck on this stuff...I'm not. If I'm at your site and it's your first time I will be giving you the same "drives for dummies" training. It's all in the "drives for dummies" book that comes with a drive but it's hidden in all the warnings that never get read or in the "specs" that don't tell you what's important and what's not.


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## telsa (May 22, 2015)

Forget 3-phase motors.

You want to learn controls.

That can best be done with 1-phase motors -- of low power -- even 12VDC.

Once you'd got things nailed down, you can bump up the voltage and phases.

No problem.


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## goodtimesgladly (Sep 12, 2017)

You do not need a motor to learn controls as you only need the control components such as breakers, contactors, switches etc. There are thousands of schematics online to follow and you can simulate the motor starting and stopping by your contractor clicking in and out. Once you learn control and I would practice both 2 and 3 wire starting as maintained or momentary contact control. Please do not use the capacitor method to simulate 3 phase as you will never use it in real life. Using a VFD on the other hand will allow you to run your 3 phase motor on single phase and this is something you probably will use at some time or another. Now you can make your motor spin and you can learn VFD programming and wiring methods such as "paulengr" suggested.
Find a drawing and get it approved by someone who can supervise and get yourself the components you need and learn the start and stop simulation.
Then get your VFD and practice your 3 phase and programming but remember it is easy to cook a VFD if you do not follow the book.


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## paulengr (Oct 8, 2017)

You can just as easily cook a motor with a VFD as you can cook the VFD itself. A local feed mill cooked 3 or 4 motors recently after a 10 year flawless run. Motor was only 1 HP but was located about 200 feet from VFD. The external output line reactor went bad and all the motors had just the first couple turns shorted out. Classic reflected wave problem. Put in a new filter and trouble free ever since. You can't really easily find this one without a scopemeter or taking the bell end off and knowing what to look for in the motor.


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## micromind (Aug 11, 2007)

paulengr said:


> You can just as easily cook a motor with a VFD as you can cook the VFD itself. A local feed mill cooked 3 or 4 motors recently after a 10 year flawless run. Motor was only 1 HP but was located about 200 feet from VFD. The external output line reactor went bad and all the motors had just the first couple turns shorted out. Classic reflected wave problem. Put in a new filter and trouble free ever since. You can't really easily find this one without a scopemeter or taking the bell end off and knowing what to look for in the motor.


I've never seen a reactor go bad but I have seen more than a few motors burn up because of reflected wave. Even spike-resistant ones if they're far enough from the VFD.


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## John Valdes (May 17, 2007)

Here's low cost alternative to a phase converter.

https://motorsandcontrol.com/kb-ele...ut-ip-20-enclosure-variable-frequency-drives/


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## Dennis Alwon (May 9, 2009)

Mike , I am sorry but I need to close this thread. You may be an electrician but you are way out of your experience and it does look like a diy job. This is not something to look at lightly and i personally feel you should get some experienced mechanic in there to help with this.


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