Connecting a pws/delta run/ y-start motor

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Electron_Sam78

Electron_Sam78

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Hey all just want your input on connecting a pump house motor 200 hp 460v 3 ph with availability for connecting in PWS, Delta Run, or Y Start. It has a motor control center with a Altistart 48 Y-Range soft starter. The supply power is 480 Y system. My question is would this be connected in the Delta configuration when using the Altistart 48? There are 4 motors in the pump faciIity, which is a standby facility where the pump systems only get exercised weekly for 10 mins, and 2 have burned up in 5 years. They are currently connected in the Delta Run configuration. Seems like a high burn up rate.

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If using soft starter you connect motor same as you would for across line starting - which would be the delta configuration.

Wye connection is for starting only when used with wye-delta starting controller.

By placing motor coils in a delta configuration you apply full supply voltage to each individual coil. 480 volts in your case is applied across each motor coil.

By placing motor coils in a wye configuration and still supplying 480 input volts - you reduce the voltage seen by each coil by a square root of three factor, each coil only sees 277 volts. This is only done to reduce inrush current and is only for brief period then the control switches to the delta connection which is the run mode.

I would suspect you possibly have misconfigured motor leads, improper voltage, undersized motor for the application, mechanical issue causing overload to name a few possibilities.
 
+1 on all of the above. My bet is on misconfiguration of the motor connections. The motor would have to be seriously under sized for it to burn out from running 10 minutes per week. Assuming you mention all of those choices because that's on the motor nameplate, I'd bet you have a 12 lead motor. That can be a little daunting for someone not used to them.

The fact that you mentioned that your power system is 480V Wye is not really germane, but that leads a lot of guys to misinterpret and think that the motor must be connected in Wye to match. Those issues have nothing to do with each other. You connect the motor for full voltage. In this case, it's likely Delta.

If the motor is connected correctly, look for a phase current imbalance. If there is one, it could be a bad connection somewhere or even a defective soft starter. Low current on one phase causes the motor to over heat even if there is no overload condition.
 
We verified the connections on the burned up motor and they were correct. The voltage is fine. As far as undersized I wouldn't know about that. That's an engineering issue. I will check the phase loads on start up of the new unit.

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Electron_Sam78 said:
We verified the connections on the burned up motor and they were correct. The voltage is fine. As far as undersized I wouldn't know about that. That's an engineering issue. I will check the phase loads on start up of the new unit.

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So when you say "voltage is fine", measured where? Again, if the soft starter is malfunctioning and not giving full voltage to one phase, you can damage a motor very quickly yet never see it as an overload. Measure current on the output side of the soft starter while raming and running. The Altistart doesn't have a built-in bypass contactor, so if they didn't wire one in separately, the motor is being fed by the SCRs full time. If one of them fails to fire correctly, you get a sever current imbalance.
 
Jraef said:
So when you say "voltage is fine", measured where? Again, if the soft starter is malfunctioning and not giving full voltage to one phase, you can damage a motor very quickly yet never see it as an overload. Measure current on the output side of the soft starter while raming and running. The Altistart doesn't have a built-in bypass contactor, so if they didn't wire one in separately, the motor is being fed by the SCRs full time. If one of them fails to fire correctly, you get a sever current imbalance.
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We use Square D (Telemechanique, now) softstarts up to 500HP on most of our pump installations and we run pumps sometimes 24/7. But...almost all have isolation and bypass contactors. Those that don't still have very few problems, though. If installing a bypass is not feasable, I'd be taking a hard look at the softstart settings and output currents/voltages starting and running. Also look at installing a relatively inexpensive phase monitor that provides both overcurrent and imbalance trips. Cheap insurance against motor failure and downtime. If you have access to a power analyzer/recorder, that would tell you what's really going on. Should not really ever fail if all is correct. Ours last years. All of our part-winding start are Wye start, Wye run. Just some thoughts.
 
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Jraef said:
So when you say "voltage is fine", measured where? Again, if the soft starter is malfunctioning and not giving full voltage to one phase, you can damage a motor very quickly yet never see it as an overload. Measure current on the output side of the soft starter while raming and running. The Altistart doesn't have a built-in bypass contactor, so if they didn't wire one in separately, the motor is being fed by the SCRs full time. If one of them fails to fire correctly, you get a sever current imbalance.
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Measured at line side if panel CB. We haven't started the new one yet. We will definitely take measurements at the soft starter once we start the new one. I believe there are bypass contactors installed.

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Electron_Sam78 said:
Hey all just want your input on connecting a pump house motor 200 hp 460v 3 ph with availability for connecting in PWS, Delta Run, or Y Start. It has a motor control center with a Altistart 48 Y-Range soft starter. The supply power is 480 Y system. My question is would this be connected in the Delta configuration when using the Altistart 48? There are 4 motors in the pump faciIity, which is a standby facility where the pump systems only get exercised weekly for 10 mins, and 2 have burned up in 5 years. They are currently connected in the Delta Run configuration. Seems like a high burn up rate.

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Click to expand...
You've been given some sound advice here. If, as you seem to think, a bypass contactor has been fitted there are a couple of other things I would check.
Whether the bypass contactor is definitely coming in when the motor gets to speed.
And the motor current in all three phases when the motor is in bypass to make sure that they are balanced and within the nameplate rating of the motor.
 
Jraef said:
So when you say "voltage is fine", measured where? Again, if the soft starter is malfunctioning and not giving full voltage to one phase, you can damage a motor very quickly yet never see it as an overload. Measure current on the output side of the soft starter while raming and running. The Altistart doesn't have a built-in bypass contactor, so if they didn't wire one in separately, the motor is being fed by the SCRs full time. If one of them fails to fire correctly, you get a sever current imbalance.
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I assume "raming" is a typo? LOL. Is that Google-Auto-Correct-Eese for "starting"?

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The configuration of the motor panel is the incoming power circuit comes into a main CB then from load side goes to line side of a second CB. Then from the second CB it goes to the line side of 2 Schneider LC1F330 contactors. The load side of each of those goes to the line side of the soft starter and the others to a set of terminals on the bottom that are behind the load terminals where the motor circuit connects.

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Electron_Sam78 said:
The configuration of the motor panel is the incoming power circuit comes into a main CB then from load side goes to line side of a second CB. Then from the second CB it goes to the line side of 2 Schneider LC1F330 contactors. The load side of each of those goes to the line side of the soft starter and the others to a set of terminals on the bottom that are behind the load terminals where the motor circuit connects.

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Hmmm...

You say there are two CONTACTORS. Is one of them hopefully a STARTER, as in a contactor with an overload relay? Because if not, then that might be part of your problem. If the second contactor is the bypass for the soft starter, you need to have an overload relay in that circuit, because once the soft starter is bypassed, it might not be protecting the motor any longer because it no longer sees the current. It would depend, of course, on the exact configuration and termination points, I can't see it from here because my crystal ball is on the fritz. But that might partially explain the failures. If the load is too much for the motor, but the bypass contactor bypasses the OL protection, you are running them to destruction.

It's actually a more common mistake than one might imagine. In fact, here is a PUBLISHED sketch from a manufacturer that shows this EXACT situation;

soft-starter-wiring-diagram-5437.jpg
Notice that when the bypass contactor would shunt power around the soft stater, there is no OL relay. It's totally irresponsible for the soft starter mfr to publish this, but it's a cheap Chinese product, so there you go.

Here is what it SHOULD look like:
50674.jpg
The "825..." module above the soft starter is essentially the OL relay, so no matter what path the motor power takes, it STILL passes through that device and is sensed, so the electronic overload protection is intact.
 
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Jraef said:
Hmmm...

You say there are two CONTACTORS. Is one of them hopefully a STARTER, as in a contactor with an overload relay? Because if not, then that might be part of your problem. If the second contactor is the bypass for the soft starter, you need to have an overload relay in that circuit, because once the soft starter is bypassed, it might not be protecting the motor any longer because it no longer sees the current. It would depend, of course, on the exact configuration and termination points, I can't see it from here because my crystal ball is on the fritz. But that might partially explain the failures. If the load is too much for the motor, but the bypass contactor bypasses the OL protection, you are running them to destruction.

It's actually a more common mistake than one might imagine. In fact, here is a PUBLISHED sketch from a manufacturer that shows this EXACT situation;

View attachment 14152
Notice that when the bypass contactor would shunt power around the soft stater, there is no OL relay. It's totally irresponsible for the soft starter mfr to publish this, but it's a cheap Chinese product, so there you go.

Here is what it SHOULD look like:
View attachment 14153
The "825..." module above the soft starter is essentially the OL relay, so no matter what path the motor power takes, it STILL passes through that device and is sensed, so the electronic overload protection is intact.
Click to expand...
I see your concern but take a look at this from the Altistart 48 manual page 39:
" On all controllers, the motor protection features are available even if a shorting/bypass contactor is used to bypass the SCRs after the motor is up to speed. To assist with troubleshooting, the 3-digit LCD displays status codes. The controller memory registers and maintains the previous 5 status codes, even following power loss. Thermal Overload Protection The ATS48 controller is a UL Listed motor controller with integrated motor and controller thermal protection. The motor and controller temperature are continuously calculated based on the controller nominal current and the current that is actually drawn. An electronic circuit, which stores the thermal state of the motor even if the supply power is disconnected, simulates the cooling curve. Overload of any kind over any duration can cause the motor temperature to rise. As Figure 19 shows, the ATS48 controller creates a digital model of the motor temperature based on two thermal images. The first (T1) represents the level of temperature rise corresponding to iron (motor frame). The second (T2) represents the temperature rise of copper (stator, windings). For each thermal image, two levels of alarm are detected. An overload pre-alarm is signaled by logic output LO1 when the motor has exceeded its nominal temperature rise threshold. A pre-alarm is signaled when the thermal state exceeds 105% for T1 and/or 130% for T2. A thermal fault signal stops the motor when the temperature rise exceeds the critical threshold. A thermal fault is signaled by relay R1 when the motor thermal state exceeds 110% for T1 and 140% for T2."

As I stated previously one set of conductors from one contactor goes to the line side of the soft starter. Then the other set of conductors from the other contactor go to the bypass terminals of the soft starter. It seems from the manual that even with a bypass circuit (as long as it is connected through the bypass terminals) receives motor overload protection.

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As I stated previously one set of conductors from one contactor goes to the line side of the soft starter. Then the other set of conductors from the other contactor go to the bypass terminals of the soft starter.
Click to expand...
Well, technically that isn't what you said.
... and the others to a set of terminals on the bottom that are behind the load terminals where the motor circuit connects.
Click to expand...
I interpreted that to mean a free-floating set of terminals down stream of ("behind") the soft starter. I was obviously wrong, but your choice of words was more accurate this time.

So OK, it looks like that works, because this is what it looks like inside of that soft starter.

ATS48 bypass.JPG

So if you follow the path, terminating on those "Bypass" terminals routes the power flow through the CTs so that the soft starter is monitoring the current. If it truly is connected EXACTLY like they show, then it should be fine and that's not what's making your motors fry.

If however the installer terminated on the wrong set of terminals, it wouldn't work right. But if so, it would not soft start either, it would bang on when the bypass contactor closed. Probably not that then either.

The other possibility is that something else is controlling the bypass, i.e. a manual or otherwise external circuit, so even IF the soft starter detects the OL, the bypass contactor is not dropping out. I've seen that happen. When you use the soft starter to protect the motor all of the time, you MUST allow the soft starter to be the ONLY thing that controls the bypass contactor. Similarly, and I've seen this too, someone decides that once bypassed, they don't need the soft starter any more and they power it down, effectively eliminating it's protection features (which also requires something EXTERNAL controlling the bypass). Check those possibilities too.

If it's none of the above, and you have checked to make sure you have balanced current flow to the motor, then it's on to more unlikely theories. I have dozens of those :p
 
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Jraef said:
Well, technically that isn't what you said.

I interpreted that to mean a free-floating set of terminals down stream of ("behind") the soft starter. I was obviously wrong, but your choice of words was more accurate this time.
Click to expand...

Yeah sorry I didn't know what the bypass terminals were called before I looked through the manual online so I tried to describe where they were connected on the soft starter.


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