Burned motors

[Dan86]

I'm a new maintenance man at a small business. My electrical knowledge is limited and growing daily. The previous maint. Guy installed a 3 phase 220v system from the panel to a disconnect and disconnect to the motors. The motors are able to be high or low voltage with a 208v capacity as well. What is the proper way to wire these systems. Like I said both are internally wired for low voltage which is what's available 220. There is a 15 amp 3 pole breaker, wired to the disconnect which Is unfused then from the disconnect directly to the motors. The system was put online and both motors fried after running for a period of time. We thought the bearings or gearboxs were shot but it seemed odd that both motors were smoked. Any insight would be greatly appreciated.

 

[Another C10]

I'm a new maintenance man at a small business. My electrical knowledge is limited

I would suggest reading the specifications of the motors and make sure your power supply is designed for such a motor.
If that doesn't make enough sense, maybe just hire a licensed electrician to be liable for the installation, it may be cheaper.

 

[iceworm]

Couple of questions:

1. I have not seen a 220V system since the 1970s. Did you actually measure the phase to phase voltage?
2. What is the system? Corner grounded Delta? Centertap grounded delta? Ungrounded delta? Something else?
3. The way you describe the connection, there are no contactors or overloads - is that true?
4. What type and size are these motors?

With the limited information we have, my suggestions are:
After you replace the motors

1. Verify the existing supply (voltages, phases)
2. Verify the new motors are correct for the existing supply
3. Install CB, contactor, and correct sized overloads - for each motor
4. Verify the CB is the correct size for the motors.
5. If the motors start and don';t trip the CBs or overloads, immediately measure the running current.

As suggested, some help is a good idea.

 

[paulengr]

I'm a new maintenance man at a small business. My electrical knowledge is limited and growing daily. The previous maint. Guy installed a 3 phase 220v system from the panel to a disconnect and disconnect to the motors. The motors are able to be high or low voltage with a 208v capacity as well. What is the proper way to wire these systems. Like I said both are internally wired for low voltage which is what's available 220. There is a 15 amp 3 pole breaker, wired to the disconnect which Is unfused then from the disconnect directly to the motors. The system was put online and both motors fried after running for a period of time. We thought the bearings or gearboxs were shot but it seemed odd that both motors were smoked. Any insight would be greatly appreciated.

So far in general it sounds completely illegal. This sort of thing can cause a fire and the insurance company is going to question whether or not to pay for it. No overload protection. If you had this and the motor was actually overloaded it would just trip the relay, not burn up. It is legally required in every state in North America and most of the rest of the world, The breaker might do short circuit, maybe. Just not enough detail. Based on the description maybe the wiring is grossly undersized.

The issue here as you said is you’re out of your element. You stated nothing about the motor name plate. Plus if you know motors you would know the 230 V motors typically run fine on 208 V. This isn’t your issue. Any industrial electrician should know that. It’s something else but the “starter” if you call it that is nonexistent. This is like hanging a light fixture from twisted wires, just dangerous;

Either your predecessor didn’t know anything either or worse knew but did something stupid and dangerous anyway. Motors are not something you can learn from a book sold at Home Depot. You really need to get professional help.

I’d strongly suggest you get an electrical contractor or two to look at it and quote what you need done. You will get the free advice you are after which will confirm what I am saying and some idea of what it will cost to fix it properly. That’s assuming the motor is properly sized for the load, which is also questionable,

 

[Russs57]

Dan86, my easy way to remember it is as follows. This assumes a standard 9 lead 3 phase motor suitable for 208/240/480.

L1, L2, and L3 always connect to your incoming power lines. For high voltage you connect 3 & 6 together, 4 & 7 together, and 5 & 8 together. Notice the wire numbers are three apart. For low voltage 1 and 7 together, 2 and 8 together, and 3 and 9 together. Notice they are six apart. The remaining wires, 4/5/6 get hooked together.

Warning, not all motors get wired the same. Always use the nameplate diagram. However the above is the most common type.

Do some reading up on motor starters. Why I will use an IEC type I’d advise a NEMA one.

 

[ActionDave]

Dan86, my easy way to remember it is as follows. This assumes a standard 9 lead 3 phase motor suitable for 208/240/480.

L1, L2, and L3 always connect to your incoming power lines. For high voltage you connect 3 & 6 together, 4 & 7 together, and 5 & 8 together. Notice the wire numbers are three apart. For low voltage 1 and 7 together, 2 and 8 together, and 3 and 9 together. Notice they are six apart. The remaining wires, 4/5/6 get hooked together.

Warning, not all motors get wired the same. Always use the nameplate diagram. However the above is the most common type.

Do some reading up on motor starters. Why I will use an IEC type I’d advise a NEMA one.

That's only true for star wound motors.

For star or delta the high voltage hook up is the same.

For a delta low voltage you tie 1,6,7 together, 2,4,8 and 3,5,9.

 

[infinity]

I'm a new maintenance man at a small business. My electrical knowledge is limited and growing daily. The previous maint. Guy installed a 3 phase 220v system from the panel to a disconnect and disconnect to the motors. The motors are able to be high or low voltage with a 208v capacity as well. What is the proper way to wire these systems. Like I said both are internally wired for low voltage which is what's available 220. There is a 15 amp 3 pole breaker, wired to the disconnect which Is unfused then from the disconnect directly to the motors. The system was put online and both motors fried after running for a period of time. We thought the bearings or gearboxs were shot but it seemed odd that both motors were smoked. Any insight would be greatly appreciated.

What is the exact line to line voltage at the 15 amp, 3 pole circuit breaker?

 

[Metallicbeing]

Hi Dan86,
From your post, it looks like you're in that most precarious position. You know just enough to get yourself in trouble. If you're not knowledgeable enough to setup a Motor Starter (or know that there should have been one there already), then I would suggest that you tell your boss to have an Electrical Contractor re-do this install. You can then see what a proper install looks like and learn from that. For now, you're a Maintenance Electrician, but as you get more knowledge under your belt, you'll better understand these things (forgive me if you're further along in your education than is shown above).

At this point, I think it would be irresponsible for you to dabble in this area (with your company's assets). Equipment Loss and possibly Personal Injury are likely, if this isn't done correctly. You should definitely research this area for your job. I wish you well on what will, hopefully, be an exciting and interesting career.

 

[Beaches EE]

Dan86, it is time to bring in a licensed electrician.