Motor Connections

[aharrigan]

Is there a standard for connecting motors to the line feeding them? For example a 480 volt
20 HP three phase motor. The feed from source is #4's so L1-L2 and L3 are nutted and bolted
to T1-T2and T3.

What about the other leads that get spliced together ( # 10's ) for instance, are these to be nut and bolt
or will wire nuts be ok in the nose bag? Wire nuts have a voltage rating but I don't see any amperage rating.

Motor manufacturer info does not address this as far as I can see.

 

[petersonra]

Is there a standard for connecting motors to the line feeding them? For example a 480 volt
20 HP three phase motor. The feed from source is #4's so L1-L2 and L3 are nutted and bolted
to T1-T2and T3.

What about the other leads that get spliced together ( # 10's ) for instance, are these to be nut and bolt
or will wire nuts be ok in the nose bag? Wire nuts have a voltage rating but I don't see any amperage rating.

Motor manufacturer info does not address this as far as I can see.

wire nuts do not have an amperage rating because they are just a mechanical connection. They carry no current. In fact some are completely plastic.

I am not a huge fan of bolt and tape as it is very labor intensive, but it works. There are faster ways that work as well.

 

[Jraef]

wire nuts do not have an amperage rating because they are just a mechanical connection. They carry no current. In fact some are completely plastic.

I am not a huge fan of bolt and tape as it is very labor intensive, but it works. There are faster ways that work as well.

Motors always mean vibration. For that reason, wire nuts are totally inappropriate, they are NOT intended for use in applications that involve vibration. Mechanical clamps such as insulated tap connectors (often called "Polaris Connectors" after a main brand) or split bolts (a.k.a. "Kearnys") are alternatives to crimp-on connectors + bolts and nuts.

"Polaris" connector:

"Kearny" split bolt:

 

[petersonra]

Motors always mean vibration. For that reason, wire nuts are totally inappropriate, they are NOT intended for use in applications that involve vibration. Mechanical clamps such as insulated tap connectors (often called "Polaris Connectors" after a main brand) or split bolts (a.k.a. "Kearnys") are alternatives to crimp-on connectors + bolts and nuts.

"Polaris" connector:
View attachment 9409
"Kearny" split bolt:
View attachment 9410

some tape around the wire nut and it will stay on forever regardless of any vibration. I am not fond of wire nuts in general, but they can be made to work.

 

[don_resqcapt19]

Motors always mean vibration. For that reason, wire nuts are totally inappropriate, they are NOT intended for use in applications that involve vibration. ...

While I don't like wirenuts for motors Ideal says many of their wirenuts are for use for 3 phase motor connections (I expect that other manufacturers say the same).

 

[kwired]

I've used "wirenuts" on smaller conductors for years, only real problem I am aware of was once on a "shaker" machine where the motor had a lot of vibration because of the nature of the machine. This motor required higher maintenance than many others because of the excess vibration (primarily bearing replacement) so you didn't want to have to cut the leads every time you took it out of service so certain methods that are difficult to disassemble were not that desirable either, we packed the terminal box with fiberglass insulation and have had no trouble since.

 

[kwired]

Motors always mean vibration. For that reason, wire nuts are totally inappropriate, they are NOT intended for use in applications that involve vibration. Mechanical clamps such as insulated tap connectors (often called "Polaris Connectors" after a main brand) or split bolts (a.k.a. "Kearnys") are alternatives to crimp-on connectors + bolts and nuts.

"Polaris" connector:
View attachment 9409
"Kearny" split bolt:
View attachment 9410

I have used split bolts quite a bit on larger conductors. A few years ago decided to try the polaris connectors, had one fail pretty in pretty short time, but maybe wasn't tightened properly IDK.

Now I question whether or not they are rated for fine strand conductors that are often used for motor leads.

 

[petersonra]

I have used split bolts quite a bit on larger conductors. A few years ago decided to try the polaris connectors, had one fail pretty in pretty short time, but maybe wasn't tightened properly IDK.

Now I question whether or not they are rated for fine strand conductors that are often used for motor leads.

the normal polaris style connectors are not rated for fine stranded wire but they make some that are. i think they have a different insulation color.

 

[Jraef]

While I don't like wirenuts for motors Ideal says many of their wirenuts are for use for 3 phase motor connections (I expect that other manufacturers say the same).

One of the most catastrophic VFD failures I have ever seen was the result of blue wire nuts used to connect a mobile gravel pit vibrating screen motor. The contractor made the argument that "they were rated for it" as his reason for ignoring common sense. Two wire nuts backed off, the motor leads went to the case, tires insulated it from ground, no ground return wire to the VFD so it just kept pumping power to the vibrating feeder frame until everything blew up. Had anyone come along and given that frame a gound path by just touching it under operation, they would have been severely burned or killed. Luckily it was a two man operation, so it never happened since they were always in tractors if the machine was running.

 

[iwire]

One of the most catastrophic VFD failures I have ever seen was the result of blue wire nuts used to connect a mobile gravel pit vibrating screen motor. The contractor made the argument that "they were rated for it" as his reason for ignoring common sense.

Well you have picked one of the most severe duty applications that can be imagined.

We always use wirenuts when we can and have no issues, of course these are usually fans, pumps, door operators etc.

For a vibrator motor I might go another route, those are always a problem. The wires supplying the motor often short out in the flex or when we use rubber cord the cords short out from the shacking.


Bottom line,if you don't want contractors to use wirenuts put it in the specifications.

 

[petersonra]

Bottom line,if you don't want contractors to use wirenuts put it in the specifications.

we have a winner!

 

[don_resqcapt19]

One of the most catastrophic VFD failures I have ever seen was the result of blue wire nuts used to connect a mobile gravel pit vibrating screen motor. ...

Failures in that application are not uncommon. Screener instructions often call for the motor terminal box to be filled with duct seal to prevent vibration damage to the conductors and connections.

 

[petersonra]

the normal polaris style connectors are not rated for fine stranded wire but they make some that are. i think they have a different insulation color.

I looked it up. the normal ones appear to have black insulation while the ones rated for fine stranded conductors have grey insulation.