3000W Chinese Gensets Info.
professor95 wrote: EDIT ADDED 45/5/2013- When this thread started in March of 2005, I never expected to see it survive this long or amass the quantity of information that has been shared here. In...
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I stop by now and then as you guys are having so much fun there.
This issue brings back memories of a large caliber machine gun problem I was called on to fix. After the gun was operated in burst mode for a minute or so, it would all of a sudden start shooting at full speed while the trigger had no control of stopping the gun. To make a long story short, the trigger activated a relay which activated a solenoid that initiates the shooting. The solenoid has a large inductance. Once current flows through an inductor, the inductor will do everything in its power to maintain that current even when the relay wants to turn the current off. As the relay contacts start to open, the solenoid generates an extremely large voltage that's large enough to ionize the air gap between the relay contacts. Current will continue to flow until the relay contacts have moved far enough apart. The spark that keeps current flowing heat the contacts. A succession of firing bursts create enough heat to weld the relay contacts together, resulting in an uncontrollable gun. The fix was to add a capacitor between the relay contacts. As the contacts opened, current continues to flow by way of the capacitor. By the time the capacitor is fully charged, the contacts are far enough apart to prevent a spark from occurring.
I've also seen this problem with a grinder. The switch contacts on this grinder had welded shut. The only way to turn it off is to pull the plug.
The voltage spike created by opening up contacts to an inductor can be pretty powerful. The larger the inductance, or the larger the current, or the faster the turn-off time, the larger the induced voltage.
V = -L * di/dt
Sal
This issue brings back memories of a large caliber machine gun problem I was called on to fix. After the gun was operated in burst mode for a minute or so, it would all of a sudden start shooting at full speed while the trigger had no control of stopping the gun. To make a long story short, the trigger activated a relay which activated a solenoid that initiates the shooting. The solenoid has a large inductance. Once current flows through an inductor, the inductor will do everything in its power to maintain that current even when the relay wants to turn the current off. As the relay contacts start to open, the solenoid generates an extremely large voltage that's large enough to ionize the air gap between the relay contacts. Current will continue to flow until the relay contacts have moved far enough apart. The spark that keeps current flowing heat the contacts. A succession of firing bursts create enough heat to weld the relay contacts together, resulting in an uncontrollable gun. The fix was to add a capacitor between the relay contacts. As the contacts opened, current continues to flow by way of the capacitor. By the time the capacitor is fully charged, the contacts are far enough apart to prevent a spark from occurring.
I've also seen this problem with a grinder. The switch contacts on this grinder had welded shut. The only way to turn it off is to pull the plug.
The voltage spike created by opening up contacts to an inductor can be pretty powerful. The larger the inductance, or the larger the current, or the faster the turn-off time, the larger the induced voltage.
V = -L * di/dt
Sal
jasult wrote:toprudder wrote:jasult wrote:
I explained to him what was going on and he instantly told me that the 15 amp grinder was not the problem however when I release the load there is a voltage spike and these champs have a safety device to protect any thing plugged in if there is a spike and shuts down genny. He said that big electric motors can cause this spike.
That is called "electrical fast transient".
toprudder, thanks - I never saw the mention of this problem on this site and it is only when I ran my 15 amp grinder and releasing the trigger. At leaast I know now what to do when running a large electric motor. The Tech (Adam) was great and very fast response time in helping me get to the answer in seconds. Again, the solution is to just unplug the BLACK wire from the shut off switch if the spike activates the shutdown.
