Generator harmonics

[technoid]

For many weeks now I have been trying to trouble shoot my MEP 803 that has an AC voltage induced in the DC control circuit for the glow plugs. I have gone through many tests and tracings for obvious shorts. I have checked or replaced the battery charging alternator, the A1 regulator and wiring. This ghost voltage as I call it is 55 VAC @1200- 1300 hz. From what I have been reading this may be what is known as a fault in the windings. And this can produce harmonic RFI. When my genset runs and not connected to anything it knocks out my digital flat screen TV. There is a way to filter out this voltage but I am at a loss on how it can be done. I have attached a site link that talks about generator harmonics.

 

[Scoobyshep]

Make sure you have a healthy neutral to ground bond for starters. I've never seen it done with a generator but with motors and drives we used to use a line reactor to filter out weird harmonics.

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[technoid]

Make sure you have a healthy neutral to ground bond for starters. I've never seen it done with a generator but with motors and drives we used to use a line reactor to filter out weird harmonics.

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The neutral and bond are not connected on the 803. That is code. And the unit was made that way from the factory.

 

[Scoobyshep]

Floating neutrals only work if you are using phase to phase loads. Without the bond you get weird voltages.

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[wheelspinner]

The Neutral and bond are not connected on the 803. That is code. And the unit was made that way from the factory.

How are you connected? If the unit is not bonded, it must be bonded at the breaker panel with a proper earth ground.

 

[technoid]

Floating neutrals only work if you are using phase to phase loads. Without the bond you get weird voltages.

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This 803 is set up for my home 120/240 service. The national electric code states not to ground the Neutral to the bond on the generator side. This is code . And all of the 803, 802 are wired this way. It's the same as a sub panel load center. No neutral bonding on a sub panel. So this is not the harmonic problem that I have.

 

[Scoobyshep]

This 803 is set up for my home 120/240 service. The national electric code states not to ground the Neutral to the bond on the generator side. This is code . And all of the 803, 802 are wired this way. It's the same as a sub panel load center. No neutral bonding on a sub panel. So this is not the harmonic problem that I have.

It depends if there is a switching action on your neutral if you're switching the hots only then do not bond the generator if you are switching the neutral as well then you need to bond the generator.

If you are running with a bond in the system can be at your panel if you're not switching the neutral then we need to move on and find what your actual problem is just eliminating the stupid variables

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[Guyfang]

There is a thread in the forum over this problem. The short of it is this. The only way this happens is when the 24 volt alternator has a bad diode in it. Disconnect the wires at the alternator. Tape them off, start the set and see if you still have the problem.

 

[technoid]

It depends if there is a switching action on your neutral if you're switching the hots only then do not bond the generator if you are switching the neutral as well then you need to bond the generator.

If you are running with a bond in the system can be at your panel if you're not switching the neutral then we need to move on and find what your actual problem is just eliminating the stupid variables

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Your preaching to the quire. I am a retired commercial electrician. The neutral is not switched here. This problem is with the windings. This genset functions normal when loaded. You would never know there was a problem until you check with a fluke meter for inductive voltage. I need to know what type of filter can be placed on the prime mover outputs that would ground out this voltage. The only other alternative is to have the generator re-wound. And that is not an expense I can afford at this time.

 

[Scoobyshep]

Hard to tell online. Alot of people make very bad mistakes with grounding and bonding (master electrician turned engineer here). You will need a 1 to 1 transformer to filter. Its size is determined by the output current. To prove the concept you can use a smaller transformer to test (in a pinch you can use 2 identical transformers back to back (ie a 208 to 480 to a 480 to 208 ) or search the bay of e for a line reactor.

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[Daybreak]

This 803 is set up for my home 120/240 service. The national electric code states not to ground the Neutral to the bond on the generator side. This is code . And all of the 803, 802 are wired this way. It's the same as a sub panel load center. No neutral bonding on a sub panel. So this is not the harmonic problem that I have.

Howdy,
All MEP generators have a bonding strap. It is either connected, or not connected.
A MEP generator connected to a house service panel with 4 wires, making use of the service panel neutral, ground system, then the bonding strap is disconnected on the MEP.

 

[technoid]

Hard to tell online. Alot of people make very bad mistakes with grounding and bonding (master electrician turned engineer here). You will need a 1 to 1 transformer to filter. Its size is determined by the output current. To prove the concept you can use a smaller transformer to test (in a pinch you can use 2 identical transformers back to back (ie a 208 to 480 to a 480 to 208 ) or search the bay of e for a line reactor.

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Thank you sir. I will look into it.

 

[robson1015]

Choir

 

[technoid]

Choir

Guess I lost the spelling bee, LOL!

 

[technoid]

Hard to tell online. Alot of people make very bad mistakes with grounding and bonding (master electrician turned engineer here). You will need a 1 to 1 transformer to filter. Its size is determined by the output current. To prove the concept you can use a smaller transformer to test (in a pinch you can use 2 identical transformers back to back (ie a 208 to 480 to a 480 to 208 ) or search the bay of e for a line reactor.

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I want to order this reactor transformer on eBay: GE Fanuc Line Reactor Transformer, A81L-0001-0122 02, Used, WARRANTY
But will it work for single phase? Can I run the neutral through it along with both 240 wires each in one of the 3 phase connections?

(link removed)

 

[Scoobyshep]

As long as the reactor is rated for the voltage and amperage it should be fine.

Did you look at the field diodes?

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[technoid]

As long as the reactor is rated for the voltage and amperage it should be fine.

Did you look at the field diodes?

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I don't think it's the Exciter diodes. This genset produces full 100% power with no problem. And I have been told not to use the center coil on the reactor forgot a neutral filter. Just the two outer coils for 240 volt for single phase use.

 

[glcaines]

Howdy,
All MEP generators have a bonding strap. It is either connected, or not connected.
A MEP generator connected to a house service panel with 4 wires, making use of the service panel neutral, ground system, then the bonding strap is disconnected on the MEP.

I have a question. Why is it bad to leave the jumper in place bonding neutral to ground at the generator when using the generator to power a house? To clarify, I have the following situation.
I have an MEP003A that is trailer mounted and that is connected to my house via a 400 amp manual transfer switch. The transfer switch only switches the L1 and L3 lines and splits them to feed two separate 200 amp panels in the house. The L0 neutral from the generator is not switched, but is permanently wired to the two 200 amp panels in the house, which are tied to a ground rod at the house. I ran 4 wires from the generator, the L1 and L3 lines, the L0 neutral and a separate ground line. The ground line is connected to both the generator and trailer frame and the other end to the ground at the main panel in the house. The jumper is still in place on the generator bonding the neutral to ground. The reason I preferred to leave the jumper in place is that I have a lot of acreage and use the trailer mounted genset to frequently provide power remotely. When I use it remotely, I drive a ground rod in and connect it to the ground lugs on the generator and trailer. The setup has been working very well for over 9 years now and I don't have any kind of interference. When it was installed, which I did myself, the local EMC sent a "generator expert" to approve my installation and the County also sent an inspector out. Both approved the installation, and I'm assuming they knew what they were doing. Is it bad to leave the neutral / ground bond in place at the generator?

 

[Daybreak]

I have a question. Why is it bad to leave the jumper in place bonding neutral to ground at the generator when using the generator to power a house? To clarify, I have the following situation.
I have an MEP003A that is trailer mounted and that is connected to my house via a 400 amp manual transfer switch. The transfer switch only switches the L1 and L3 lines and splits them to feed two separate 200 amp panels in the house. The L0 neutral from the generator is not switched, but is permanently wired to the two 200 amp panels in the house, which are tied to a ground rod at the house. I ran 4 wires from the generator, the L1 and L3 lines, the L0 neutral and a separate ground line. The ground line is connected to both the generator and trailer frame and the other end to the ground at the main panel in the house. The jumper is still in place on the generator bonding the neutral to ground. The reason I preferred to leave the jumper in place is that I have a lot of acreage and use the trailer mounted genset to frequently provide power remotely. When I use it remotely, I drive a ground rod in and connect it to the ground lugs on the generator and trailer. The setup has been working very well for over 9 years now and I don't have any kind of interference. When it was installed, which I did myself, the local EMC sent a "generator expert" to approve my installation and the County also sent an inspector out. Both approved the installation, and I'm assuming they knew what they were doing. Is it bad to leave the neutral / ground bond in place at the generator?

Howdy,
By the electrical gods wisdom, you do not want 2 points of ground. The generator expert might not have known exactly what a MEP generator is. You run 4 wires to the house to make 4 connections. I am sure your house service panel has more than 1 ground rod in the ground. So consider that as the master grounding point. If things are wet, and something rubs the wrong way, and you touch the generator metal, the ground bond plate is in place, you have a ground loop, which means a opportunity for you to become the ground.
Can you get away with leaving it? YES
Is it proper? NO
Can you be struck by lightning? YES
Have you? NO
When things go south, you do not want to be the ground.
Can a generator simply run in the field without a ground rod? YES
Is it safe? NO

If you brought out that generator expert and pointed out the bonding strap on the genset, and and really looked over what was connected to where... He would say he made a mistake. And pray no one got hurt due to his mistake.

Now, there is also a whole other world known as permanently mounted genset. This is where a fully automatic transfer switch comes into play, which might switch 4 wires. But that itself is way different from a MEP.

 

[technoid]

Howdy,
By the electrical gods wisdom, you do not want 2 points of ground. The generator expert might not have known exactly what a MEP generator is. You run 4 wires to the house to make 4 connections. I am sure your house service panel has more than 1 ground rod in the ground. So consider that as the master grounding point. If things are wet, and something rubs the wrong way, and you touch the generator metal, the ground bond plate is in place, you have a ground loop, which means a opportunity for you to become the ground.
Can you get away with leaving it? YES
Is it proper? NO
Can you be struck by lightning? YES
Have you? NO
When things go south, you do not want to be the ground.
Can a generator simply run in the field without a ground rod? YES
Is it safe? NO

If you brought out that generator expert and pointed out the bonding strap on the genset, and and really looked over what was connected to where... He would say he made a mistake. And pray no one got hurt due to his mistake.

Now, there is also a whole other world known as permanently mounted genset. This is where a fully automatic transfer switch comes into play, which might switch 4 wires. But that itself is way different from a MEP.

Final note.. I spoke with a generator supplier. He told me they connect the ground to the generator frame because of lightning. A direct strike to the service has taken out many a generator sold that did not have the generator grounded to the frame. I personally did the no code thing and put the ground strap back on my 803. I can't see how a ground loop can happen to shock hazzard if you are bonded at both ends and both ends have double grounding rods. The green wire carries any possible short. Just like a power tool shorting to it's case. If the ground point of the plug is connected and you are holding the shorted tool you don't get a shock. The ground rod only protects against lightning. And a short to ground strong enough to hurt you should trip the breaker.