3 phase submersible water well tripping out on current unbalance intermittently.
Pump is set 400' deep and served 480/277. Franklin submersible pump and motor with Franklin's SubMonitor control. Control is programmed to the limit of 10% current unbalance.
Checked today with a PQA at the starter and voltages were as good as anyone could expect. Within a volt of each other. Currents were 74.4, 74.9 and 66.1. THDv was under 3%. Sine wave was perfect. I use the rule of 1% voltage unbalance can cause 6-10% current unbalance. Rolled the conductors at the starter serving the motor and the high and low legs stayed on the line conductors.
This suggest a supply side problem to me. Thermal was used on the gear we could open with no hot joints identified. Measured currents and volts back at the POCO's metering set and saw the same good volts and the same unbalanced currents.
I can't explain the unbalanced currents that will exceed 10% and cause the SubMonitor to trip the motor out. I have not been at the well when it tripped out. We are installing a recorder tomorrow. How can the currents be so far out if voltage is balanced and the low current stays on the source phase not the motor lead?
This is a water supply company that has three submersibles. Only this pump is large enough that Franklin requires the SubMonitor be used to keep the warranty on the pump. Replacement is $8K, so it will not be run without the SubMonitor. There are no issues with the two smaller pumps that just have starters.
Thanks,
Pump is set 400' deep and served 480/277. Franklin submersible pump and motor with Franklin's SubMonitor control. Control is programmed to the limit of 10% current unbalance.
Checked today with a PQA at the starter and voltages were as good as anyone could expect. Within a volt of each other. Currents were 74.4, 74.9 and 66.1. THDv was under 3%. Sine wave was perfect. I use the rule of 1% voltage unbalance can cause 6-10% current unbalance. Rolled the conductors at the starter serving the motor and the high and low legs stayed on the line conductors.
This suggest a supply side problem to me. Thermal was used on the gear we could open with no hot joints identified. Measured currents and volts back at the POCO's metering set and saw the same good volts and the same unbalanced currents.
I can't explain the unbalanced currents that will exceed 10% and cause the SubMonitor to trip the motor out. I have not been at the well when it tripped out. We are installing a recorder tomorrow. How can the currents be so far out if voltage is balanced and the low current stays on the source phase not the motor lead?
This is a water supply company that has three submersibles. Only this pump is large enough that Franklin requires the SubMonitor be used to keep the warranty on the pump. Replacement is $8K, so it will not be run without the SubMonitor. There are no issues with the two smaller pumps that just have starters.
Thanks,
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