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Chinese motor question

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jrjr2u

jrjr2u

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I was given a dust collector that presents as new. The motor plate states 220 volt and 50hz. From what I gather the 50hz is a non issue as their support said it is fine on 60hz. The next issue is that this has a 120v plug on the cord. They stated that after changing the plug to a 220v plug it will work as intended here in the states. Inspected the wiring and found that the ground wire that is fastened to the motor frame also passes through the 3 pole switch and is switched along with the power leads. I find this very strange and wouldn't think a ground should be switched.
Is there some anomaly in China that requires a switched ground? In China or other countries is there actually 220v supplied on one wire and completes with a neutral? I have no experience with Asian or European standards. I was going to install the plug and go for it but thought it would be worth the conversation first. Thanks for any info.
 
jrjr2u

jrjr2u

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petersonra said:
Chinese supplied equipment often has anomalies like this.

I would be inclined to move the incoming EGC to the frame so it is not switched.
Click to expand...
Yes I agree. I am more interested in the power delivery really. As I understand it in other countries 240v is supplied on one leg and the circuit is completed with a neutral much the same as 120v is in the US. Here I would be supplying split phase.... power on 2 legs and no neutral. I have read this will work fine but would like to understand it a bit better.
 
petersonra

petersonra

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jrjr2u said:
Yes I agree. I am more interested in the power delivery really. As I understand it in other countries 240v is supplied on one leg and the circuit is completed with a neutral much the same as 120v is in the US. Here I would be supplying split phase.... power on 2 legs and no neutral. I have read this will work fine but would like to understand it a bit better.
Click to expand...
It works the same. the electrons do not care if the wire is a grounded conductor or not.

The only difference is during a fault. the fault path might be a little different depending on where the fault occurs.
 
jrjr2u

jrjr2u

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petersonra said:
It works the same. the electrons do not care if the wire is a grounded conductor or not.

The only difference is during a fault. the fault path might be a little different depending on where the fault occurs.
Click to expand...
What works the same? With split phase each phase carries the unbalanced load of the other phase. I guess I don't quite understand the internals of the motor. Maybe that's it. Should I just install the 220v plug and test? Side note- there is a capacitor inline with one phase.
 
petersonra

petersonra

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There is only one phase in a two wire system like this. If one of the wires is a grounded conductor (sometimes called a neutral) it does not change how the system works at all. The amount of current is the same in both wires.

The capacitor is probably the start capacitor. If you look more closely it is likely you will see it is not "in line" but the other side of the capacitor is wired to a centrifugal switch that opens up once the motor is close to full speed. The start capacitor is used to generate a phase difference to get the motor moving with a single phase motor like this. In a three phase motor this is not needed because the 3 phases inherently provide this phase difference.
 
jrjr2u

jrjr2u

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petersonra said:
There is only one phase in a two wire system like this. If one of the wires is a grounded conductor (sometimes called a neutral) it does not change how the system works at all. The amount of current is the same in both wires.

The capacitor is probably the start capacitor. If you look more closely it is likely you will see it is not "in line" but the other side of the capacitor is wired to a centrifugal switch that opens up once the motor is close to full speed. The start capacitor is used to generate a phase difference to get the motor moving with a single phase motor like this. In a three phase motor this is not needed because the 3 phases inherently provide this phase difference.
Click to expand...
The capacitor is most definitely inline with one side. The supply wire comes into the wire housing on the motor, connects to one side of the capacitor and the other side of the capacitor connects to one of the power wires entering the motor. The other wire entering the wire housing on the motor goes directly into the motor. The third wire connects to the motor frame, (ground)
I used the term phase in error. Sorry. Each of the 2 branches carry 120v out of sync with the other for 220. There would be no neutral in a 220v setup.
 
Little Bill

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In other countries, they only have 220V (approx.) and that is one line to neutral, not leg to leg. Their motors are rated as such. So to use them here on a split phase system is fine. All the motors are looking for is 220V. It doesn't care if it's line to line or line to neutral. Some equipment will not like the 60hz here but some doesn't matter.
As to the OP, I would do as suggested and remove the ground (EGC) from the switch and just go motor to frame to EGC from the circuit.
 
LarryFine

LarryFine

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The motor doesn't know or care whether the enter tap of its supply, or one line of its supply, is grounded. It only cares about the voltage between its two supply lines.

When you connect a multi-voltage ballast to 208v, the white ballast wire is connected to a line conductor, not a grounded conductor. It doesn't care, still works fine.
 
jrjr2u

jrjr2u

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LarryFine said:
The motor doesn't know or care whether the enter tap of its supply, or one line of its supply, is grounded. It only cares about the voltage between its two supply lines.

When you connect a multi-voltage ballast to 208v, the white ballast wire is connected to a line conductor, not a grounded conductor. It doesn't care, still works fine.
Click to expand...
Ok then, thanks! I will put the 220 plug on and see what happens. That cap doesn't seem right though.......
 
Jraef

Jraef

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The cap assembly may have another internal connection that you cannot see, i.e. this is a PSC motor with the cap outside.
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If it is a centrifugal blower, the motor would have to be significantly over sized to be able to handle the added load at 60Hz.
Power requirement on a centrifugal blower increases at the CUBE of the speed change. so at 120% speed (50Hz design getting 60Hz), the power required FROM the motor will be 1.2 x 1.2 x 1.2, or 173% of what the blower needs at 50Hz. So either the 1.5HP motor only needed to be 0.87HP and they almost doubled it for possible use on 60Hz, or the fan is going to require 2.59HP from a motor only rated for 1.5HP and the motor will overload. The fact that the Chinese can't even get the wiring configuration correct leads me to believe this is going to overload.

Good luck with that...
 
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