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Ptc warning, Current imbalance protection, Current imbalance trip – Rockwell Automation 193-EC1_2_3_5, 193-ECPM,592-EC1_2_3_5 E3 and E3 Plus Solid-State Overload Relay User Manual User Manual

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Rockwell Automation Publication 193-UM002I-EN-P - December 2011

Chapter 3 Protective Trip & Warning Functions

Parameter 30, OL/PTC ResetMode, allows the user to select the reset mode for
the E3 Plus Overload Relay after an overload or thermistor (PTC) trip. If a PTC
trip occurs and automatic reset mode is selected, the relay will automatically reset
when the PTC resistance drops below the reset resistance. If manual reset mode is
selected, the E3 Plus Overload Relay must be manually reset after the PTC
resistance drops below the relay’s reset resistance.

PTC Warning

The E3 Plus Overload Relay will immediately indicate a PTC warning if:

• no warning currently exists,
• PTC Warning is enabled, and
• resistance across terminals 1T1 and 1T2 is either greater than the E3 Plus

Overload Relay’s response resistance or less than the short-circuit trip
resistance.

When the PTC warning conditions are satisfied, the:

• TRIP/WARN LED will flash an amber 8-blink pattern,
• bit 7 in Warning Status, Parameter 15, will set to “1”, and
• bit 1 of Device Status, Parameter 21, will set to “1”.

Current Imbalance

Protection

A current imbalance can be caused by an unbalance in the voltage supply, unequal
motor winding impedance, or long and varying wire lengths. When a current
imbalance exists, the motor can experience an additional temperature rise,
resulting in degradation of the motor insulation and reduction of life expectancy.
Rapid Current Imbalance fault detection helps extend motor life expectancy and
minimize potential damage and loss of production.

Current Imbalance can be defined by the following equation:

%CI = 100% * (I

d

/I

a

)

where

%CI = Percent Current Imbalance

I

d

= Maximum Deviation from the Average Current

I

a

= Average Current

Current Imbalance Trip

The E3 Overload Relay will trip with a Current Imbalance indication if:

• no trip currently exists,