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3 phase starter circuit

madmachinst

Stainless
Joined
Jan 15, 2007
Location
Central FL
Here it is.
3 phase controller.jpg

I am wondering where and what rating fuses I should add? I know for sure for the VFD I need fusing. will the 200 amp contactor to the left need fusing for its coil? Anything else like maybe MOV on the 10 amp cube relay. Pony motor is a 3hp TEFC motor and idler is this thing. 50 HP Baldor TEFC
50 hp baldor.jpg
Is there anything wrong with my wiring scheme? Have no idea yet what amount capacitance I need for the legs.
I've already taken a serious detour with the pony motor starter. I don't want to hear anything about Peddling.
 

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rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
I use a manual breaker that also acts as a door entry lock when the lever is turned to power on. The breaker is like this:

ABB - KXTBRHEBFP - RHE_B Base for Extended Handle Breaker Operating Mechanism for XT1, XT3 Breakers - Allied Electronics & Automation

The handle I use is a Fujitsu but this is similar:

SQUARE D Handle Length 3 in Handle Assembly, Disconnect Switch Size':' 250 A - 5B048'|'9421LH3 - Grainger

The setup allows manual on/off with door entry locked out when power is applied.

Your question about fuse protection for the coils. I have never had the need for that.
 

madmachinst

Stainless
Joined
Jan 15, 2007
Location
Central FL
I had a funny feeling protecting fuse coils is not really a thing. I don't feel like I need a door lock switch. I am the only one with the door key and want it powered up when working in there. So everything else looks feasible?
 

rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
If your coils were 24VAC and that voltage was coming from a control transformer (120VAC to 24VAC) then a fuse holder might be built onto
the top of the transformer.

It would be a good idea to wait around for more inputs. I don't like that small relay yet.
 

madmachinst

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Joined
Jan 15, 2007
Location
Central FL
It would be a good idea to wait around for more inputs. I don't like that small relay yet.

Now mind you Originally I wanted to go with a 15 amp cube relay and send the NC leads straight to the VFD, guy at automation direct talked me into using the 32 amp contactor for the 3hp VFD. Other than that it is switching to the 120VAC coil 200 amp rated contactor. Not powering any motors directly.
 

rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
If the VFD has a power-up sequence that delays the full operation then those first few seconds are eaten up.
A VFD I own takes between 5-10 seconds for initialization.

The manual for that VFD states that to many contact closures on the input side will damage the VFD. Something like no more than one closure
every 2 minutes.

Looks like it should work.
 

J_R_Thiele

Stainless
Joined
Jan 22, 2003
Location
Columbia Missouri
From what you have posted I cannot tell if you plan on using any run or balancing capacitors. If you are, I would suggest having them connect by a contactor controlled by the relay controlling the 200 amp motor contactor.

Spinning up the idler with capacitors connected will allow any residual magnetism to make the idler function as a generator. This can lead to significant inrushing amperage spikes, instead of the decrease in inrush amps anticipated.

I was not aware of this when I experimented with using a VFD to spin up a 10hp idler. In measuring the single phase inrush amps I found a low of around 11 amps- and a high of 160 some amps. Most measurements were more moderate, but spikes of 4 times the 3 phase FLA of 28 amps were not uncommon. (Converting 3 Phase amps to the single phase equivalent requires multiplying by 1.732. The the 10 HP 28 amp 3 phase FLA is 48.5 amps of single phase current. I was "only" 3.3 times that).

With a 40 hp motor having FLA of 104 in 3 phase, the single phase FLA is 180 amps. A significant increase in that
that single phase inrush current could be an issue with a 200 amp contactor.
 

madmachinst

Stainless
Joined
Jan 15, 2007
Location
Central FL
Totally new and revamped idea here. Junk the VFD. 1 phase pony motor 2 HP TEFC is like $266 and 3 phase is $203 and don't forget the need for $250 VFD. $266 vs $453 is a no brainer. Going with a timer relay and contactors for pony motor and idler ( already have that one in a box).
3phase II.jpg

In the pic on the IDEC timer relay base, screw #3 is not being used, red wires go straight from 25 amp contactor to latching push button.
 

madmachinst

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Joined
Jan 15, 2007
Location
Central FL
From what you have posted I cannot tell if you plan on using any run or balancing capacitors. If you are, I would suggest having them connect by a contactor controlled by the relay controlling the 200 amp motor contactor.

That 200 amp contactor is input side to the idler motor. I plan on putting the balance caps between the idler and the 3 phase load panel. I am all ears regarding hearing out what kind of problems I can expect with the caps. Only time in the past when I ran huge caps was on a cnc power supply. I had to create a soft start circuit using these humongous resistors cause the caps were blowing my breakers ( after two fuses went to breakers) every time during power up.
 

J_R_Thiele

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Joined
Jan 22, 2003
Location
Columbia Missouri
With a pony motor system, if the run caps are connected to the idler when the idler is spinning it can be a problem. It is not going to matter where they connect or where they physically are. They store electrical energy, and if there is sufficient residual magnetism in the idler they allow the voltage to increase. Going from memory, I was getting voltages of over 240 in about 10 to 20 seconds. I was able to hook up a 3 phase coolant pump and run it (the only small 3 phase motor I have).

Have your timer activate a second contactor to connect the capacitors at the same time the power connects to the idler.

In your diagram you are indicating the timer set for 12 to 20 seconds. That seems like a long time to me. Make it as short to limit the possible "generator" potential.

If you can do so in a safe way, set up the components for a trial run before finalizing the design. I did this with components mounted to plywood so I had plenty of room and it was easy to change and rearrange things. That gave me a much better idea of what I needed, and how to arrange it in the electrical cabinet.
 

J_R_Thiele

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Joined
Jan 22, 2003
Location
Columbia Missouri
Correct.

For others reading this thread:

If L1 and L2 are the single phase lines and L3 is the generated phase, "run" ( or "balance") capacitors would go between L1 and L3, and also L2 and L3. Because they are continuously connected they should be oil filled capacitors. They adjust the voltage between the 3 lines. The challenge with this is that the capacitance needed varies with the load, and usually the load varies- so you adjust for the most common situation you have. It is possible to add them on each machine, so they are connected only when that machines motor is powered.

If you were not using the pony motor, and the RPC was 10 HP or smaller, you could use electrolytic "start" capacitors to help start the idler and determine its direction of rotation. These would go between L1 and L3 or L2 and L3, depending on the desired direction of rotation. They are disconnected after a second or so when the motor has started. They are connected by a contactor controlled by a manual pushbutton, a timer, or a device that senses voltage being generated in L3. When you get to idlers of over 10 HP they become challenging to use due to the capacitance needed and the contactors welding closed. When this happens the capacitors overheat and vent, or explode.
 

madmachinst

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Joined
Jan 15, 2007
Location
Central FL
This one is a 1750 RPM 50 hp idler
50 hp baldor.jpg
and I hope the 2 hp pony will be enough to get it running. the 2hp motor is 3600 rpm motor, so will be using pulley on it that is 1/2 the diam of the idler pulley. I expect that work.
 

J_R_Thiele

Stainless
Joined
Jan 22, 2003
Location
Columbia Missouri
Somehow I thought you had a 40 HP idler.

A 50 HP 3Phase motor at 230 volts will have 130 FLA if connected to 3 phase power. Connecting it to single phase power gives a FLA of 225. Per the 2014 NEC the ampacity of the conductor for you RPC (assuming variable loads) needs to be at least 125% of the FLA of the converter factory nameplate. Making your own means you do not have that name plate. What are the FLA of the machines you will run on the converter simultaneously?

Per the 2014 NEC the conductor ampacity needs to be at least 125% of the converter FLA. The Overcurrent protection needs to be not more than 125% of the converter FLA. The disconnecting means can be by a circuit breaker, a molded case switch, or a switch rated in HP. The Circuit breaker or molded case switch needs an amp rating of not less than 115% of the converter FLA.

225 FLA single phase amps X 1.25= 281 amps.
225 " " " " x 1.15= 259 amps

If we use those as a guideline, your 200 amp contactor is not large enough. It may work, but for how long?
I would suggest looking for a used NEMA 5 motor starter. That is rated for a 100 HP 3 phase motor (FLA amp 248). That would be more than enough. With some time shopping around you can get them at reasonable prices. They are heavy, so pay attention to shipping. Also pay attention to the coil voltage. If you go the E bay route- look for the "make offer". These are not a high turnover item. Someone will want the shelf space back.
 

TDegenhart

Diamond
Joined
Mar 26, 2011
Location
Geneva Illinois USA
Two issues I see. The latching PB will automatically restart the system on a power outage. This not safe. Use a momentary NO push button with a latching contact from the timer and a NC stop button. That way if the power goes out, the latching contact opens and prevents auto restart. If in fact you will be drawing greater than 200 amps, then the contactor and wiring will need to be sized accordingly. The contacts on the timing relay may not be heavy enough for the coil starting requirements. For example, a size 5 contactor has nearly 2600 VA coil inrush. You will have to verify the inrush requirements of the smaller contactor. It is common to interpose a machine tool relay between a timer and the controlled load.

Tom
 

madmachinst

Stainless
Joined
Jan 15, 2007
Location
Central FL
I only got 195 amps to spare after lights and air conditioning. TD I see what you are saying. will have to go back to latching the relay instead of a latching power button. JR I am not seeing what you are talking about full load amps when I have a pony motor getting this thing to synchronous speed and its a shaft running with no load on it. Why even bother bringing up FLA? Lathe I have has been run by other people here with as little as 80 amp 3P breaker, I plan on giving it 100 amps ( in single phase that means 173 amps). Mill when I will have that running off 3 phase will be like 25 amps at most. BTW my contactor is an ABB EH145. It just doesn't seem to have that power resistor on the side by the coil.
 

J_R_Thiele

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Joined
Jan 22, 2003
Location
Columbia Missouri
Why am I talking about FLA? That is a good question.

At the start of this thread you indicated that you had a 50 HP Baldor motor for an idler that you intended to pony start. The single-phase power to the motor was going through a 200 amp contactor. There is no mention of what the RPC will be powering, or what the available electrical service is.

You are using a pony start RPC to reduce the starting inrush current. In my first post (#7) I mentioned my experience with having capacitors in the circuit while using a pony motor and finding that sometimes the inrush current was increased instead of decreased. I used a reference to this as a multiple of the FLA as it is an easy way to calculate what could happen with a different motor.

Where I got “off” was in post #14. The NEC uses FLA as a way to specify the required conductor size, overload protection, and disconnect size for phase converters. BUT- this is the FLA stated on the manufacturer nameplate on the phase converter, not the nameplate on the idler motor. My calculations based the idlers FLA --ARE NOT-- appropriate for a pony start RPC.
Because you are “manufacturing” your own phase converter, you can design it to your own specifications and create your own nameplate.

What the NEC wants that nameplate to have are: Manufacturer’s name, input and output voltages, HZ, rated single-phase input full load amps, rated minimum and maximum single load in kVA or HP, Maximum total load in kVA or HP, and for a RPC, 3 phase amps at full load.

You have some decisions to make. If you can safely do so, wire up your components, try it out, and measure what actually happens in starting the RPC, and what amps it uses at idle.

Decide the maximum HP motor you will start. Keep in mind that your RPC will have the full inrush current of any motor started, in addition the running current of the RPC, and the running current of any additional motors running at the time.

FYI
I have read many times that the inrush current is typically 5 or 6 times the FLA. I just tried to confirm this, and it is used as a rule of thumb- but to accurately calculate it you use the locked rotor letter code stamped on the nameplate to tell you the locked rotor kVA per HP, multiply this by the Nameplate HP and calculate the amps based on the voltage supplied.
 

madmachinst

Stainless
Joined
Jan 15, 2007
Location
Central FL
Thanks for the clarification JR and all your help. I am just going off suggestions I had gotten from other vendors in teh past I didn't go with. One guy from TX said that I can power his rotaphase for 30 hp unit w/ 100 amp breakerand rated wire. That was cap start. here I am talking pony start so it really should be less. Now keep in mind will have caps on the idler, but when pony starts rotating it, it will be totally isolated from anything because the contactor will be in NO state. will bleed resistor help to alleviate what you were talking about regarding run /balance caps where you said, "They store electrical energy, and if there is sufficient residual magnetism in the idler they allow the voltage to increase." My contactor is actually a 3 pole contactor, think I would have any benefit running the wild leg through that third leg back to the 3 phase panel. This way I can connect L1-L3 via balance caps and L2-L3 again via balance caps through the contactor on the output lugs, but when the contactor is open no problems with the caps? Or will I just end up blowing caps?
 

J_R_Thiele

Stainless
Joined
Jan 22, 2003
Location
Columbia Missouri
I sent you a PM with a link I believe you will find helpful.

It would help me understand what you intend if you were to draw it all out.

With the Pony motor RPC I believe you will need at least two contactors.
You do not want L1 or L2 connected to the 3 phase breaker box until after the RPC is started.
 








 
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