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Generators & Electric Motors General Discussion Antique Generators and Old Electric Motors: Questions and answers about restoring and showing old power generation systems.

Generators & Electric Motors General Discussion

Three phase genset build.. Questions


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  #11  
Old 02-18-2019, 10:02:48 PM
Wayne 440 Wayne 440 is online now
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Default Re: Three phase genset build.. Questions

From a distance, my guess is that flashing it can't hurt the existing situation. From the referenced page - " To flash it momentarily connect a car battery across the generator output terminals while it is running full speed ‘with no load’. ONE second is more than enough time...".
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  #12  
Old 02-18-2019, 11:39:47 PM
Kurtis Kurtis is offline
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Default Re: Three phase genset build.. Questions

Quote:
Originally Posted by DMeed View Post
I'm trying to figure out how a 575V motor is creating 240V.

Is there a quick primer on using induction motors as generators?

Also how is a motor/generator that is rated 5.25 amps is going to supply power to a motor that takes 10 or 12 amps at 240V

I would second the rotary phase converter idea.
Hi DMeed.. thank you. I realize now that I need a much bigger motor. I am wonder what a 14 hp engine could comfortably power. The present location of the saw has single phase but I don't have any grid services at my shop so three phase generators would be benificial. Especially since I see a lot of that kind of equipment laying around for the price of scrap metal. I am a bit confused by all the numbers listed on the saw motor as far as amps go. Somebody else mentioned that it was 6.1 amps. Can that motor be configured that many different ways?

Quote:
Originally Posted by Radiomike View Post
This is an induction generator, it depends on having some residual magnetism to start generating with the capacitors proving the leading VARs for excitation. It has to be run at super-synchronous speeds usually around 50 to 100 rpm above nominal synchronous. There is a good wiki article on estimating the required capacitance. https://en.wikipedia.org/wiki/Induct...tor#Excitation it also details the use of DC to start the self excitation process. The value of the capacitors determine the voltage. I note your blue motor has a rated voltage of

If you suspect the capacitors then check then with a "Megger" for ground faults and a series resistance and use three voltmeters to calculate the value of Xc. Note the capacitors have an internal 1Mohm internal resistor. , They should however test clear of ground.

Have you thought of a rotating phase convertor. A bank of capacitors and a pilot motor would be a lot simpler, unless you need an independent source. Another option is a variable speed (VSD) unit these have a 240volt single phase input and a 240V three phase output. https://www.ebay.ca/i/182935786653?c...d=2&dispItem=1

https://www.amazon.com/Variable-Freq.../dp/B07CJXQWVT

I see your blue motor is rated at 575V and 5 amps but the red motor is 6.1 Amps at the highest voltage

Mike
Thank you Radiomike. The wiki article was exactly what I needed to see. Especially this part: An induction machine can be started by charging the capacitors, with a DC source, while the generator is turning typically at or above generating speeds. Once the DC source is removed the capacitors will provide the magnetization current required to begin producing voltage.

An induction machine that has recently been operating may also spontaneously produce voltage and current due to residual magnetism left in the core.

I don't know how many articles that I have read that didn't say anything about that. All say the residue current will build up.

Quote:
Originally Posted by Radiomike View Post
I assume your Panel saw is like this https://www.youtube.com/watch?v=4MAsVT693E4.

The schematic for the control looks complex but is mostly a series of interlocks to prevent mal and mis-operation and to maintain safety for the operator. There must be an English version available somewhere. Any induction generator will struggle to provide not only the motive power but the correct voltage for the auxilliary circuits, and what appears to be a single phase fan. Using an induction generator will give large voltage swings when the main motor is switched on and off. The control circuit and its transformer will not be happy being subjected to large over-voltages.

The duct tape covered wiring on the main motor is a source of some concern. Has someone been modifying the wiring and bypassing the safety interlocks?

One suggestion is a VFD for the main drive and a single phase supply to the control circuit and exhaust fan. Or a rotary phase convertor which can maintain a closer voltage.

From the schematic it looks possible to separate the single phase parts from the three phase parts.

Mike
Hi RadioMike.. Yes it is model 1265 built in 1992. From what I gather so far, the motor is three phase, the automated counter balance is two phase, and there is a small transformer in the electrical box that is single phase, which I assume runs the sensors. Lol, the duct tape actually serves no purpose, I should have taken it off so as to not confuse things further. Turns out that a pin dropped out of the saw which actuates a mechanism that locks the saw in place before it will start up. Appears somebody wasn't very observant and thought it was an electrical problem so they messed around with the wires.

I am wondering, if I put a bigger motor on and put and a bigger bank of caps on, if it would level out power surges.

Quote:
Originally Posted by Radiomike View Post
This is an induction generator, it depends on having some residual magnetism to start generating with the capacitors proving the leading VARs for excitation. It has to be run at super-synchronous speeds usually around 50 to 100 rpm above nominal synchronous. There is a good wiki article on estimating the required capacitance. https://en.wikipedia.org/wiki/Induct...tor#Excitation it also details the use of DC to start the self excitation process. The value of the capacitors determine the voltage. I note your blue motor has a rated voltage of

If you suspect the capacitors then check then with a "Megger" for ground faults and a series resistance and use three voltmeters to calculate the value of Xc. Note the capacitors have an internal 1Mohm internal resistor. , They should however test clear of ground.

Have you thought of a rotating phase convertor. A bank of capacitors and a pilot motor would be a lot simpler, unless you need an independent source. Another option is a variable speed (VSD) unit these have a 240volt single phase input and a 240V three phase output. https://www.ebay.ca/i/182935786653?c...d=2&dispItem=1

https://www.amazon.com/Variable-Freq.../dp/B07CJXQWVT

I see your blue motor is rated at 575V and 5 amps but the red motor is 6.1 Amps at the highest voltage

Mike
Sorry Mike, forgot to ask. Isn't it kind of dangerous jump starting a 240v system with a 12v battery?
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  #13  
Old 02-19-2019, 11:17:11 AM
Radiomike Radiomike is offline
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Default Re: Three phase genset build.. Questions

The red motor, which is the saw motor, can be configured two ways "Y" or "Δ". The motor is desined for two frequencies 50 and 60 HZ, The name plate has 50//60Hz. and the connections given as Δ/Y So the four current ratings are first the 50Hz then a // and the 60HZ. Each of the two connections are in order so the currents are (50HZ Δ) (50HZ Y) // (60HZ Δ) (60HZ Y).

Although it is not clear from the schematic if running on 220 3phase or 440 3Phase you must need to change tappings on the control transformer.

The use of DC is to provide a brief amount of magnetic flux to start the self-excitation process. Without this flux, be it a flash or sufficient residual, nothing happens - no volts.

Your saw motor look to be in Y or higher voltage configuration. I would check and voltage tappings on the control transformer.

If you have a single phase supply it is an easy matter to power the control circuit only and function check the control circuit and logic. The contactors should energise and every thing should work except the main saw motor.

Mike
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  #14  
Old 02-28-2019, 06:14:32 PM
Kurtis Kurtis is offline
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Default Re: Three phase genset build.. Questions

Quote:
Originally Posted by Radiomike View Post
The red motor, which is the saw motor, can be configured two ways "Y" or "Δ". The motor is desined for two frequencies 50 and 60 HZ, The name plate has 50//60Hz. and the connections given as Δ/Y So the four current ratings are first the 50Hz then a // and the 60HZ. Each of the two connections are in order so the currents are (50HZ Δ) (50HZ Y) // (60HZ Δ) (60HZ Y).

Although it is not clear from the schematic if running on 220 3phase or 440 3Phase you must need to change tappings on the control transformer.

The use of DC is to provide a brief amount of magnetic flux to start the self-excitation process. Without this flux, be it a flash or sufficient residual, nothing happens - no volts.

Your saw motor look to be in Y or higher voltage configuration. I would check and voltage tappings on the control transformer.

If you have a single phase supply it is an easy matter to power the control circuit only and function check the control circuit and logic. The contactors should energise and every thing should work except the main saw motor.

Mike
Thank you Mike for all the info and help. That 575 doesn't have any continuity between W1 & W2. Don't know how I did that, unless it's an intermittent connect somewhere.
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  #15  
Old 03-05-2019, 12:50:28 AM
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Default Re: Three phase genset build.. Questions

Updated photos... there are no markings on the wires for the windings and no schematic on the motor to show their configuration.
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Old 03-05-2019, 11:48:32 AM
Radiomike Radiomike is offline
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Default Re: Three phase genset build.. Questions

The motor connection, the correct way to connect the links, is shown in the schematic you referenced in your first posting. It looks to be in DELTA, lower voltage connection. The control transformer is marked for the two voltages, it seems to have links in and set for 240 Volt. So overall the motor and transformer seem to be set up for 240 Volt. If you decide to do some wire changes mark the wires with numbers as in the schematic and I always like to use crimps, Numbers are cheap https://www.ebay.com/itm/Cable-Wire-...frcectupt=true

Mike
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  #17  
Old 03-05-2019, 11:53:31 AM
Kurtis Kurtis is offline
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Default Re: Three phase genset build.. Questions

Quote:
Originally Posted by Radiomike View Post
The motor connection, the correct way to connect the links, is shown in the schematic you referenced in your first posting. It looks to be in DELTA, lower voltage connection. The control transformer is marked for the two voltages, it seems to have links in and set for 240 Volt. So overall the motor and transformer seem to be set up for 240 Volt. If you decide to do some wire changes mark the wires with numbers as in the schematic and I always like to use crimps, Numbers are cheap https://www.ebay.com/itm/Cable-Wire-...frcectupt=true

Mike
Thank you Mike.
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