short duration power loss

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ptonsparky

ptonsparky

Tom
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NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
I remember reading several posts asking how to hold in a control circuit during brief power interutptions.

Valmont Industries (Pivot Irrigation) uses a diode, capacitor, a resistor and a DC contactor for holding in pump circuits while the pivot is reversing directions. Normally the pump would quit as soon as the pivot motor starters lost power. Their part # is 315560. Control circuit voltage is 120V AC rectified to 120v DC for the time delay circuit.
 
I guess there might be several ways, but it's not uncommon to find a UPS installed in the power distribution section of most modern machinery control panels.
 
With a large enough capacitor, you can hold a relay's coil in for several seconds.

I've built short-duration time-delay release circuits using just that method.
 
I ran a desalting plant in Wrightsville Beach, NC that frequently went down due to "power bumps" that caused the control system (relays, 1975) to drop out.

We set up a 120 VAC generator driven directly by a motor. The motor was powered by line power and the control system was operated off the generator. The inertia of the system was enough to keep the control circuits in during the power bumps.
 
Bob NH said:
I ran a desalting plant in Wrightsville Beach, NC that frequently went down due to "power bumps" that caused the control system (relays, 1975) to drop out.

We set up a 120 VAC generator driven directly by a motor. The motor was powered by line power and the control system was operated off the generator. The inertia of the system was enough to keep the control circuits in during the power bumps.
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Nice... I like it. That's pretty much the way 120V power on ambulances is done. 12V motor coupled to a 120V generator. Super nice power.
 
kbsparky said:
Don't they use inverters these days?
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I don't know, but I've robbed a couple off old ambulances. They're a great find in a junkyard! Fantastic for the jobsite... just start the truck, hook up a couple of jumper cables, and drill out your holes.
http://www.rediline.com/
redipic.gif
 
kbsparky said:
Don't they use inverters these days?
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I think that once you start looking at inverters that actually put out a true AC sine wave the motor generator sets start looking much better cost wise.

Many inverters put out ugly AC.

A lot of the rental bucket trucks we rent will have one of these motor generator sets.
 
bob said:
A less costly solution is the use of a Ferroresonant (constant voltage) transformer. It depends on the length of the interruption. The site below give
a good explanations of the operation.


http://powerquality.com/mag/power_correcting_voltage_sags/
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Be careful.We use these as well.Make sure the loads being supported 1.do not have any inrush current 2.are not susceptible to the high output impedance of this CVT:)
 
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