monitor amperage

MBLES

Senior Member
I have a customer that has a tank filled with water/chemicals that has an auger that stays on all day. Sometimes the auger shaft breaks and motor keeps spinning that shaft is broken and there is no way of know right away without emptying the tank. Is there a way or product that is used that monitors the amperage while the motor is running that could indicate that auger/motor amperage has gone below a certain threshold and minimum amperage or power being used that is fairly simple?
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
I have a customer that has a tank filled with water/chemicals that has an auger that stays on all day. Sometimes the auger shaft breaks and motor keeps spinning that shaft is broken and there is no way of know right away without emptying the tank. Is there a way or product that is used that monitors the amperage while the motor is running that could indicate that auger/motor amperage has gone below a certain threshold and minimum amperage or power being used that is fairly simple?
This is common for centrifugal pumps and there a number of vendors of these. I don't see any reason that a pump monitor could not be used for your application. Some will even measure actual power as opposed to amps for greater accuracy. Here is one: https://www.nassarelectronics.com/e...MIz7eNztCW3gIVjcDACh0VEwq4EAQYAyABEgK8B_D_BwE
 

gar

Senior Member
181020-2357 EDT

MBLES:

You do not want to measure current. Rather you want a power monitor. Power is a much better indicator of mechanical load than is current.

.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
181020-2357 EDT

MBLES:

You do not want to measure current. Rather you want a power monitor. Power is a much better indicator of mechanical load than is current.

.
In the case of an auger in a tank of liquid as described in the OP do you think that either type would work to indicate that the shaft has broken?
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
In the case of an auger in a tank of liquid as described in the OP do you think that either type would work to indicate that the shaft has broken?
Yes, absolutely, all three. My experience is limited, but if I can do it anyone can. It may take a few tries if loaded to unloaded is minimal. Don't use the current switch in that case.
 

JFletcher

Senior Member
Location
Williamsburg, VA
A motion sensor on the driven part of the shaft would work as well. The instrumentation to implement a motion sensor to lock out the motor is beyond my experience, however motion sensors on screw conveyors were commonplace at the Wastewater plants I used to run. The Interlock system would prevent a downstream conveyor from starting if the Upstream conveyors weren't running, however in the case of a broken shear pin, only the motion sensor will notice the mismatch and shut down the affected feed screws.

If your customer is routinely snapping shafts, there is a problem. If he is snapping shear pins, you may be able to find one with a higher shear strength, though this is analogous to putting in a larger breaker in an electrical panel.

A power meter may not be able to tell the difference between a shaft running out of water an empty tank situation versus a broken shaft (ie no load). I'm also guessing that an audible alarm or something tied into a computer would be desirable to detect a broken shaft condition.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
To be the most accurate without adding a physical shaft sensor, use a kW monitor. Shaft kW changes more than current, because when the load goes away the power factor goes low and more of the current becomes reactive so it may not appear to change much. In addition, current changes with voltage so swings in line voltage affect the current. But since kW is calculated using the PF and the voltage, it represents the true shaft load, not affected by external factors. Some solid state overloads will do this for you now, so you may just need to change out your OL relay with one that does this.
 

buffalonymann

Senior Member
Location
NC
I have a customer that has a tank filled with water/chemicals that has an auger that stays on all day. Sometimes the auger shaft breaks and motor keeps spinning that shaft is broken and there is no way of know right away without emptying the tank. Is there a way or product that is used that monitors the amperage while the motor is running that could indicate that auger/motor amperage has gone below a certain threshold and minimum amperage or power being used that is fairly simple?
Zero Speed Switch on end of shaft
 

Besoeker

Senior Member
Location
UK
181020-2357 EDT

MBLES:

You do not want to measure current. Rather you want a power monitor. Power is a much better indicator of mechanical load than is current.

.
Yes, that's true. But the no load current is about a third of the FLC. It should be possible to detect a loss of load based on a reduction in current and that would be a simpler/cheaper option.
After all, you don't need to know actual power.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Yes, that's true. But the no load current is about a third of the FLC. It should be possible to detect a loss of load based on a reduction in current and that would be a simpler/cheaper option.
After all, you don't need to know actual power.
As long as you can be sure that the motor load is a large fraction of its capacity!

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