JMK

Hi All - I have a situation where the GFI outlet for testing control panels constantly and continuously trips. The outlet is a 120 VAC, 20 Amp general purpose receptacle outlet derived from a 120/208 VAC, 3 PH system. (Photo Attached) This area of the shop is used as a test lab for small 120 VAC control panels, and when the servo amps are powered on the GFI will trip. I tried to use inline filters, UPS, and ferrite cores on the amps’ power leads. The only work around… use a non GFI outlet. However the safety dept. frowns on eliminating the protective device. Have any of you come across this before? Your insight is appreciated. JMK

ch8.pdf

I believe so. I have used the software reset bit in the past. The reset stays active until the corresponding V-mem bit goes low again. You could wire your LS to a PLC input card instead of the HSC DI. Use your ladder program to trigger the software reset bit.

Gamble - I see that this post is about 4 months old... I hope the answer still finds you. I would refer to Article 378 for Non Metallic Wireways. The NEC General Provisions for Wiring Methods in Article 300.1(A) state that method for all wiring installations are covered by Article 300. However, 300.1(B) refers to UL 508 and the NFPA 79 for control equipment or listed utilization equipment. Now, the NFPA 79 allows non metallic ducts for internal wiring, but doesn't give tables for raceway fill... [79]1.5 does state that if specific provisions are not made in the publication [79], then refer to the provisions of the NEC [70]. If you look at the definition for Non Metallic Wireway in [70]378.1, it fits the bill. JMK

Hello all - I am looking for some assistance on how to size a safety contactor that will 'Disconnect' the supply voltage from (4) motors. This is what confuses me - Do I need to rate the contactor, as a disconnect (per NEC)? The four motors are as follows - (1) 1/2 HP, 208 VAC, 3PH (3) 3/4 HP, 208 VAC, 1PH Now, from what I gather out of the NEC: Disconnecting Means (Art. 100) A device or group of devices, or other means by which the conductors of a circuit can be disconnected from their source of supply. Ok, that's what the safety contactor is doing... Disconnect Means, General (Art 430.101) Part IX is intended to require disconnecting means capable of disconnecting motors and controllers from the circuit. Again, I interpret the safety contactor to do just that. Ampere rating and interrupting capacity for combo loads Art 430.110©(1) The rating of the disconnect means shall be determined from the sum of all currents...at the full load condition and also at the locked rotor condition. The combined full load and locked rotor current so obtained shall be considered as a single motor for the purpose of this requirement. The next paragraphs go on to refer the user to the tables .248-.251 for the FLC and LRC values associated with the motor. Ampere Rating in 430.110©(2) refers back to© (1), but adds the 115%... Here’s my example: Motor 1 (from above) has an FLC of 2.4 Amps (T430.250), and an LRC of 22.1 Amps (T430.251(B)), for a total of 24.5 Amps Motors 2-4 from above have an FLC of 7.6 Amps (T430.248), and an LRC of 45.8 Amps (T430.251(A)), for a subtotal of 53.4 Amps, (*3 motors) for a total of 160.2 Amps Total Motor Load (430.110©(1) is 184.7 Amps, *1.15 per 430.110©(2) = 212.4 Amps. Refer back to T430.251(B) at 208 VAC and 212 Amps would be 15 HP, which is rated at 257 Amps. So, the morale of my long winded story - Is this the correct method? I would need a Safety Contactor rated for 15 HP at 208 VAC.

For those interested: I had to do some research to apprise the safety folks… NEC 590.6 Requires GFCI Protection for Personal on all 120 VAC, 15, 20, and 30 Amp receptacle outlets installed in a temporary wiring scheme. However, the exception in 590.6(A) doesn’t make it a requirement in industrial establishments. One needs to comply with the Assured Equipment Grounding Conductor Program illustrated in 590.6(B)(2). Basically, all branch circuits need to be installed in accordance with the requirements of article 250. There must be continuity testing of the grounding system for all cord sets, receptacles, and equipment involved in the temporary install. Written records must be kept of the testing… Testing occurs before initial use, upon discovery of damage and repair, and for periods exceeding 3 months. Just an FYI – The 2011 NEC cites “Maintenance” and “Repair” to “Equipment” in the temporary wiring specifications outlined in article 590. Temporary wiring doesn’t apply to construction sites anymore. JMK

Thanks for the replies. Just for grins, we hooked up a scope... There is a about a 2 amp differencial current, which the GFCI sees as a ground fault leakage... Definitely a hair dryer in the bathtub! JMK

Taco - Good luck with this endeavor. I have been contemplating going out on my own for some time now, but never really knew how to get started.

Mike - I have employed Serial - Ethernet modules on CPLX and ML's. This allows me to hop online through the plant floor subnet. Also, I have set up some messaging between CLX and ML / CPLX processors using the ENI Module. jMk 1761-pp004_-en-p.pdf

Excellent feedback. I certainly feel better about the situation after having light shed on it from different angles. Paulengr - I like the contractor analogy. Thanks for the feedback. JMK

Season’s Greetings! Well, it’s been awhile since I last posted on here on MrPLC. I have always looked to the forums on this site to be very informative. Recently, I have made a career change. I have left the role of management and supervision. I decided to get back into the hands-on field. I have been in my position for roughly a month now. I had my first project assigned: document and resurrect an old, skeleton control panel to use on a new packaging machine. First task was to document what was actually in and going on in the control panel. This was painful. I am a pretty detail orientated individual…there was no schematic, and this control panel was thrown together with all the miscellaneous wire and control relays that were lying on the shelf. As I shagged everything out and sketched a schematic, I realized that there was no logical flow to the wiring, no color coded standard followed, and half of the wires weren’t even labeled. Furthermore, there were some mistakes. The supervising engineer gave me the low down on what the machine is supposed to do. I was told to make it happen using the current hardware (PLC and Drives), and I could order whatever miscellaneous materials that I needed. There wasn’t a finite time line given. I decided to spend a day gutting the old wiring, removing not needed components, and rewiring. While I was waiting for some parts, I did write the majority of the PLC and HMI programs. Well, yesterday I was caught off guard when the supervising engineer came by to talk about the project. He was concerned that I missed the scope of work… I didn’t understand what he was referring to, so I asked for clarification. He brought up the fact that I was spending time rewiring the panel. I explained my case on how I was simplifying the design and cleaning things up. I assured him that the PLC and HMI portion was ready, etc… His comeback is what really stuck with me. ‘This panel was working prior… you should have only needed to hook up a few wires… we should have seen motors turning by now…’ Again, I plead my case... He really didn't seem thrilled with my answers. I am I overacting by seeing ‘Red Flags’? I pride myself in a job well done. Being called on the carpet within the first month has never happened to me. Furthermore, the reason I was hired was because I brought to the table, well exactly what I’m doing – documenting, standardizing, simplifying, etc. When I was the managing guy, I wanted my group to give the same detail as I do… Your opinion is appreciated!

Stickman - I am assuming that the blower motors that you refer to are the blowers that circulate air through the 40 HP DC motor. I also assume that the blower motor is a fractional HP, 3 PH, AC motor with a separate across the line start (independent from the DC Drive). "...the display indicared a Current Minor Loop Fault and the drive shut down." Is there a CT loop on one of the blower motor leads that feeds back to the DC drive? Is there an auxiliary contact on the blower starter that connects to an input on the DC Drive? If so, that could be the relation between the blower and the DC drive and the minor current loop trip. "I checked the blower motor and found only that the starter overload block was faulty. I eliminated the overload and the blower ran fine. " Did you eliminate the overload protection, as is it's no longer in the motor circuit, or did you replace a bad overload relay or set of thermals? If so, was the unit set to the correct motor FLA? "This was completed this weekend and on power-up the blower motor went up in smoke." There was probably an original condition that caused the OL's to trip... Did you do any diagnostic testing to the motor (resistance measurement across the windings, meg windings to ground, check the across the line voltages, and get running current readings on all three legs)? You mentioned rain water leaks... Did the motors, specifically the blower motor, get wet?

Hi Splicer - Under most circumstances, if you blow 2 of 3 line fuses, there was a short circuit across that phase... If the short circuit or ground fault originated in the motor, I would suspect that the field or armature fuses would have blown. "I found some info about the motor which said there should be no less than 100,000 ohms of resistance to frame ground on either the (2) field leads or the (2) armature leads. This is to be tested with a standard ohm meter." Don't let your standard DMM fool you... I strongly suggest using a megger in the above application. A standard multi meter energizes the circuit with 3-9 VDC. With a megger, you'll check resistance in the mega ohm range using 250V - 1 kV. This is the best way to verify insulation breakdown. "Next I checked the field windings (300 V @ 15 Amp = 20 Ohms) Check also. Finally I checked resistance between the armature leads and it reads 0.2 or 0.3 ohms (This is the one I'm not too sure of)" The armature resistance seems low... I would think that you wouldn't want to see < 1 ohm. "Now for the armature. After power down I wired the armature leads back together, turned the drive speed pot all the way down and powered on the Flexpak. No boom yet I put my DC volt meter on the armature leads and slowly increased the speed pot and watched the percent current gauge and the motor shaft. I let the % current gauge get to about 25% and there was no movement from the motor shaft at all and no voltage registering on my meter, so I shut it down. (By the way, the motor shaft turns easy by hand)" This is what really catches my attention. You had 160A draw on the AC line side with 0 VDC on the armature leads? Also, at 25% you did have field voltage, but no armature voltage? Field and armature voltage should increase proportionately. I would strongly suspect that you problem lies within the drive.

Hi All... For those not aware, AB has a "recall" on Power Flex 4 and 40 drives with a FRN of 2.003 and earlier. There is a bad capacitor that fails upon power-up... Contact your AB rep for more information. With that said, I have a lot of these older PFlex drives in my plant. A good number of these drives lie on a Device Net network. Our techs get rather confused when it comes to replacing these drives... They will program the specific parameters via the keypad, but the drive / line will not run. Some of the time, the drive will fault out with a N71 (net comm loss). All of the time, the Device Net scanner will have an N78 (Identity Mis Match) with respect to the replaced node. I have to go online through RS Net Worx and correct the identity mis-match (FRN 1.007 NEQ FRN 5.001). This takes care of the network communications issue. The part that confuses me is downloading the parameters to the drive via Net Worx. I have a configuration file saved, which has all of the current parameters for each individual drive. It seems that when I / We download to the device, the parameters don't take. They stay at default... Has anyone experienced similar issues?

gmferg - Thanks for the reply! The Power Flex drives in question use a 22-COM-D interface card to link the drive to Device Net. The Node address and baud rate are fixed by the dip switches on said module. The communications faults occur when a new drive is installed (replacing an existing failed drive). The 22-COM-D module is not replaced, so the node address and baud rate aren't changed. I have narrowed the communications faults to "Identity Mis-Match" due to the FRN revision number being different than the original configuration. After I corrent the Identity issue, I proceed to "Download to Device". A process bar appears and looks as if all of the parameters are being downloaded. I "Upload fron Device" after the download completes to verift that the parameters have changed but they didn't. They all remain at default. I can change the parameters while online. That method works fine.

Paulengr - Thank you for the detailed defination! I will also bookmark this post for future reference! JmK

Hi all - I have an issue with a magnetic reed switch flow meter application. The flow meter is connected to +24 VDC and the output is connected to a high speed counter card on a PLC. Over the past few months, operations have seen inconsistent batch levels associated with said flow meter. In the near past, it was brought to my attention that after a batch is complete the batch count keeps increasing on the HMI screen. However, the valve is closed and there isn't any oil flowing in the pipe. Well, I got the O-Scope and noticed that there was noise on the signal (return from reed sw.) wire. OK - First of all, the wires were 14 awg THHN running out to the flow meter. This past weekend, I pulled in a Belden 8770 18/3 shielded cable. I terminated the drain to ground on the PLC chassis per the AB spec. Today, operations called with the same problem. The noise was still present. Again, I got out the O-Scope. This time I looked at things a little more closely... DC (+) with respect to ground had 13 VRMS ~60-80 Hz. DC (-) with respect to ground showed the same. DC (+) with respect to DC (-) showed 5-7VRMS ~60-80 Hz. Interesting I installed a jumper from DC (-) to PE. The noise has significantly decreased. I am looking for some contributing factors, and what to look at next... There are 7 AC Drives in this panel... whoever installed the drives did run 3 phase line power and motor leads in the panel wireway with low voltage control wires... Is it possibly just the drives? The 120 VAC line power is clean (verified w/ O-Scope) Am I dealing with a failing DC power supply? What can you recommend to clean up the noise in the DC system? Is grounding the DC (-) common practice? I always assumed that the line side ground on the power supply also referenced the DC common to ground. JmK

Thanks for the quick reply. The control panel is 72 X 72. The PLC is configured for 64 DC inputs, 64 DC outputs, a few analog IO, the HSC card, and a Device Net scanner. The DC control wires run in separate conduit from AC power and motor leads. However, the power and motor leads do run in the same panel wireway. The DC control power from the power supply terminate on a (+) and (-) bus. This system does live in a wash down environment, so I will have to verify corrosion on field device terminations. Since grounding the DC common, operations haven't seen any further issues. JmK

Hi all, I am curious to how the maintenance departments are set up in different industries. I grew up as a maintenance electrician. I have always been in a maintenance department that represented different skilled trades. The most detailed department I belonged to contained: Millwrights, Machinists, Pipefitters, Tinners, Electricians, and Machine Repair. Others places that I have been through had at least the segeration of mechanics and electricians. My current employer is different. We have only Maintenance Technicians. We are trying to hire on Automation and Controls Technicians now. We get electricians applying that do not fit the mechanical requirements. I explained the above paragraph, in more detail, to the powers that be... They want an Electrician, Machine Repair, Fitter, Machinist, IT guy, etc. all-in-one to walk into our shop.

Too True... I now do this on a daily basis as well, as I see that most of us do. We do employ a pay/progression system here as well. It is not an apprenticeship though. The idea of our pay/progression is equipment mastering... I don't wholly agree with this, because it doesn't really build upon a skill set. This method is pretty much a precedent causes v. effect scenario – the motor failed, so replace it. Not why did the motor fail and getting down to the root cause (troubleshooting). Back to the topic a hand. Don't get me wrong. I agree with the cross trained maintenance man. The problem that I am having is we are looking for that specialist - an electrical and controls guru. Unfortunately, the candidates that come in are strong in one aspect and weak in others. I personally feel that if they are strong electrical troubleshooters, have intermediate PLC troubleshooting skills, and a good attitude and ethic about them; then make an offer. However, there is conflict of interest regarding my pov... What's more, this area (Milwaukee, WI) was a large manufacturing center and heavily unionized. So that's what we're up against. Millwrights and machine repair guys who were not allowed to touch a wire, and electricians who were not allowed to turn a bolt. Like I mentioned before, I grew up like this. I served an apprenticeship in said environment. Upon being laid off, and as technology evolved, I decided to get an associate's degree in electronics. The next company that I worked with was also a union shop; the rules were a little more lax... Us electricians and the mechanics were thick as thieves and went on all calls together. We cross trained each other - a great learning experience.

Excellent conversation! So far everyone has stated that their maintenance departments have "jacks of all trades, but masters of none"... I went for a stroll on the local internet job services, and I noticed the same thing. However, the companies looking for Maintenance Techs (mechanical skills with the addition of PLC and Drives troubleshooting and programming) are offering a pretty low wage in comparison to companies looking for an Industrial Electrician. Where I came from, the skilled trades did everything in the premise. The machinists made the majority of the spare parts. The millwrights moved and installed the machinery. The fitters ran and replaced air, water, and steam lines. The electricians installed new power feeds and distribution equipment. We also did the entire control panel building and wiring. Some of us would write PLC programs, configure drives, etc. But, maintaining the plant equipment was the number one priority. Since we all had a sense of ownership, the installs were done "top notch". We also had the advantage of mastering the equipment, because it was installed in-house. Currently, we rely on outside contractors for 95% of the install work. Some of the last projects were done pretty sloppy and documentation is lacking. Some of the last projects were minor, where a qualified in-house millwright and electrician could have done the job better in the same amount of time... With better results, I might add, due to the ownership. I understand that in is no longer feasible for a company to keep an enormous maintenance staff. It is simply more cost effective to keep the “jack’s” staffed and contract out the big jobs.

During the time that I spent at my last employer, we had an electrical preventative maintenance program like BobLFoot describes. The only difference is that we could never buy a complete outage from production scheduling. We had to settle for 1/3 of the gear 3 times a year. All of the loads are shed at the power distribution panels associated with the "to be PMed" transformer. The secondary mains on the transformers are opened, followed by the primary main. Then the outdoor 25kV switch which feeds the primary main for one or two 25kV to 480V transformers is opened. Grounding is done on the load side of the primary and secondary mains, as well as in the outdoor switch bay so that the workers are in-between the grounds. We then remove all of the panels to the sub (indoor dry type). Buss ways are inspected for any discoloration. We do not torque the joints, as the flats on the nuts and bolts are marked with a hash mark. We'd just verify that there wasn't any movement. Terminations are checked on the breakers, and any hotspots detected in a prior IR scan are addressed. We then vacuum the bays, and wipe the insulators with damp rags, also checking cooling fans. The fuses are exercised in and out a few times, as well as dead transfer switches. The dead switchgear is exercised a few times before being closed permanently for another year. We also use this time to make sure our entire emergency Life and Safety generators, auxiliary power generators, and UPSs are doing their job.

A vector drive has more precision control of the application. Vector drives can also emulate the characteristics of DC drives, i.e. constant high torque at low speeds. For more info go HERE

Hi All - By trade, I am an electrician. After doing construction work for a number of years with a contractor, I wound up taking a position in a mid-sized manufacturing facility. We, as a maintenance group of mechanics and electricians, did pretty much everything. We didn't rely too heavily on third party contractors. That was a great learning experience. Of course, there is no better training than hands-on experience. For the most part, I'm a hardware guy. I have built numerous control panels, configured the hardware, and wrote several intermediate level PLC programs. Well, I have since moved on. I now work at a large company that is heavily automated. My job duties have also changed course... I have navigated towards more of a developmental role. I believe vendor specific training is a great start. I am looking into CLogix training soon. I have basic knowledge of Ethernet communications, data bases, and I have dabbled in VB a little. I read through these forums and see all of the expertise in the replies. So now I'll ask my questions: 1) What is the best means of getting some advanced training? 2) What are some of the courses that you controls professionals have taken? I'm just looking for ways to sharpen my skills. Thanks in advance for the replies!

Kaiser - Thanks for the detailed explanation! Today, we haven't had a fault occur...