Motor Protection Communication for Critical Loads Darrell Ouellette

Motor Protection & Communication for Critical Loads Darrell Ouellette Technology Application Specialist © 2015 Eaton. All Rights Reserved.

Motor Protection & Communication for Critical Loads • Electrical motors are used to convert electrical energy into mechanical energy that drive industry processes. • Unexpected downtime of these processes can impact revenue, safety, and quality of life. • When motors are used on critical loads, motor protection is an essential component and can provide energy savings, increased productivity, prevent premature failures and extend equipment life. © 2015 Eaton. All Rights Reserved. 2

What Causes Electrical Motor Failures? Electrical Mechanical Other • Power and power quality issues • Thermal conditions • Bearing issues • Mounting and alignment • Environment • Motor selection and sizing © 2015 Eaton. All Rights Reserved. 3

Motor Life Reduction when Overheated • One of the primary causes of electrical motor failure is excessive heat, which is caused by: • Over Current (current greater than FLA) • High ambient temperature • Poor ventilation © 2015 Eaton. All Rights Reserved. 4

Motor Life Reduction when Overheated © 2015 Eaton. All Rights Reserved. 5

How to Protect a Motor from Excessive Heat • Use a motor protection relay or more commonly known as an overload relay. • A motor protection relay is used to measure or calculate the motor thermal condition. • When the motor protection relay determines that the motor temperature is beyond design limitations, it signals a power component to deenergize the motor. © 2015 Eaton. All Rights Reserved. 6

How to Protect a Motor from Excessive Heat 3 Phase Power Motor Contactor X √ Overload Relay X √ • Motor operating with normal conditions • Motor operating with abnormal condition • Overload relay sends signal for motor starter to open © 2015 Eaton. All Rights Reserved. 7

How to Protect a Motor from Excessive Heat • Current is monitored over a period of time to calculate motor temperature. I 2 t protection curves are used. © 2015 Eaton. All Rights Reserved. 8

Motor Protection Overload Relay Types • Bi-Metallic (Thermal) Overloads • Basic Solid State (Electronic) Overloads • Advanced Solid State (Electronic) Overloads © 2015 Eaton. All Rights Reserved. 9

Bi-Metallic (Thermal) Overload Relay • Uses a strip composed of 2 metals with differing thermal characteristics. • When heated the metals expand at different rates causing the strip to bend and trip the circuit. © 2015 Eaton. All Rights Reserved. 10

Bi-Metallic (Thermal) Overload Relay • Can have fixed or adjustable settings. • Different “heater” elements for different motor amperage and protection class. • Offers basic current based protection only. • Thermal overload • Phase loss • Ambient compensation. • Not very accurate. © 2015 Eaton. All Rights Reserved. 11

Basic Solid State (Electronic) Overload • Microprocessor based trip time calculations utilize thermal memory tables. • Motor current is measured using CT’s. • Usually self powered. © 2015 Eaton. All Rights Reserved. 12

Basic Solid State (Electronic) Overload • Has a broad adjustable current range. • Selectable trip class settings. • Offers some advanced current based protections. • Current unbalance • Ground fault detection • Very accurate © 2015 Eaton. All Rights Reserved. 13

Advanced Solid State (Electronic) Overload • Utilizes much of the same technology as the Basic Solid State Overload. • Has added features for critical loads. • Voltage inputs for Line Protection • Has features for Load Protection • Typically has a display for indication. • Has communications capability. • Typically separately powered. © 2015 Eaton. All Rights Reserved. 14

Bi-Metallic Overload Motor Protection Basic Solid State Overload Advanced Solid State Overload Thermal Overload (Calculated) • Definition: • Thermal overload is a condition where current draw to a motor exceeds 115% of the full load amperage rating of an inductive motor • Source: • An increase in the load or torque that is being driven by the motor • A low voltage supply to the motor would cause the current to go high to maintain the power needed • A poor power factor would cause above normal current draw • Result: • Increase in current draw. Current leads to heat and insulation breakdown, which can cause system failure. Additionally, an increase in current can increase power consumption and waste valuable energy © 2015 Eaton. All Rights Reserved. 15

Bi-Metallic Overload Motor Protection Basic Solid State Overload Advanced Solid State Overload Phase Loss - Current (single-phasing) • Definition: • One of the three phase currents is not present • Source: • Multiple causes: loose wire, improper wiring, grounded phase, open fuse, etc. • Result: • Motor current increases in the remaining two phases to 1. 73 times the full load current causing excessive heating in the motor • Single-phasing can also lead to unwanted motor vibrations © 2015 Eaton. All Rights Reserved. 16

Bi-Metallic vs Electronic: Phase Loss © 2015 Eaton. All Rights Reserved. 17

Motor Protection Basic Solid State Overload Advanced Solid State Overload Ground Fault • Definition: • A line to ground fault • Source: • A current leakage path to ground • Result: • An undetected ground fault can burn through multiple insulation windings ultimately leading to motor failure © 2015 Eaton. All Rights Reserved. 18

Motor Protection Basic Solid State Overload Advanced Solid State Overload Phase Imbalance (Voltage* and Current) • Definition: • Uneven voltage or current between phases in a three phase system • Source: • When a three phase load is powered with a poor quality line, the voltage per phase may be unbalanced • Result: • Unbalanced voltage causes large unbalanced currents and as a result this can lead to motor stator windings being overloaded, causing excessive heating, reduced motor efficiency and reduced insulation life * Only Advanced Solid State Overload can detect Voltage Imbalance © 2015 Eaton. All Rights Reserved. 19

Motor Output During Phase Imbalance © 2015 Eaton. All Rights Reserved. 20

Motor Protection Advanced Solid State Overload Jam • Definition: • Jam is similar to thermal overload in that it is a current draw on the motor above normal operating conditions • Source: • Mechanical stall, interference, jam or seizure of the motor or motor load • Result: • To drive the additional load the motor draws an abnormal amount of current, which can lead to insulation breakdown and motor failure © 2015 Eaton. All Rights Reserved. 21

Motor/Line Protection Advanced Solid State Overload Over-voltage • Definition: • When the line voltage to the motor exceeds the specified rating • Source: • Poor line quality • Result: • Lower than rated current draw and a poor power factor. A trip limit of 110% of rated voltage is recommended © 2015 Eaton. All Rights Reserved. 22

Line Protection Advanced Solid State Overload Under-voltage • Definition: • When the line voltage to the motor is below the specified rating • Source: • Poor line quality • Result: • Excessive current draw. This increases the heating of the motor windings and can shorten insulation life. A trip limit set to 90% of rated voltage is recommended © 2015 Eaton. All Rights Reserved. 23

Line Protection Advanced Solid State Overload Power-up Delay • Definition: • Allows for staggered starting of motors and loads after a power loss • Source: • When there is a power failure, or power cycle, multiple loads come on line simultaneously • Result: • Sags affect the operation of devices and may prevent successful start-up • If power is lost to a motor driving a pump, it may be necessary to delay a restart to allow the pump to come to a complete stop to prevent backspin © 2015 Eaton. All Rights Reserved. 24

Load Protection Advanced Solid State Overload Phase Rotation (phase-reversal) • Definition: • Improper wiring, leading to phases being connected to the motor improperly • Source: • Improper wiring, leading to phases being connected improperly • Inadvertent phase-reversal by the utility • Result: • Phase-reversal can cause unwanted directional rotation of a motor • Possible mechanical failure and/or injury to an operator © 2015 Eaton. All Rights Reserved. 25

Load Protection Advanced Solid State Overload Under-Current and Low Power • Definition: • Average RMS current or average RMS power provided to the motor falls below normal operating conditions • Source: • A portion of the user's load disappears, caused by a broken belt, a dry-pump (low suction head) or a dead-headed centrifugal pump • Result: • Mechanical failure can or has occurred • Running a pump dry or running a pump in a dead-headed condition cause excessive heating, damaging expensive seals and breaking down desired fluid properties © 2015 Eaton. All Rights Reserved. 26

Load Protection Advanced Solid State Overload High Power • Definition: • The motor load is drawing more power than expected at normal operating conditions • Source: • This is typical of batch processing applications where several ingredients flow into a mixer. Out of-tolerance conditions can be detected using the High Power and Low Power settings • A second cause is when a positive displacement pump is pumping into a closed valve • Result: • If a high power fault goes undetected the result may be a batch of material that does not meet specification • If a high power fault goes undetected in a positive displacement pump application the result is severe mechanical failure of the weakest link © 2015 Eaton. All Rights Reserved. 27

Motor Life Reduction when Overheated • The primary cause of electrical motor failure is excessive heat, which is caused by: • Over Current (current greater than FLA) • High ambient temperature • Poor ventilation © 2015 Eaton. All Rights Reserved. 28

Motor Protection Advanced Solid State Overload Thermal Overload (Measured) • Definition: • Thermal overload is a condition where the measured winding temperature exceeds the motor design limitation. • Source: • In addition to the current conditions that cause a thermal overload, the sources below can cause increased thermal conditions. • Ambient temperature. • Reduced cooling capacity. • Result: • Operating above the designed ambient temperature can lead to heat and insulation breakdown, which can cause system failure. Restricted motor cooling will also lead to increased winding temperature. © 2015 Eaton. All Rights Reserved. 29

Motor Protection Advanced Solid State Overload Thermal Overload (Measured) 3 Phase Power Motor Contactor Overload Relay Temperature • A thermistor embedded in the motor windings will give an indication when the temperature design limit is exceeded. • RTD’s embedded in the motor windings will provide a measured value of the winding temperature. This temperature feedback can be used to set alarm and shutdown levels. © 2015 Eaton. All Rights Reserved. 30

What Causes Electrical Motor Failures? Electrical Mechanical Other • Power and power quality issues • Thermal conditions • Bearing issues • Mounting and alignment • Environment • Motor selection and sizing © 2015 Eaton. All Rights Reserved. 31

Motor Protection Advanced Solid State Overload Bearing Temperature 3 Phase Power Motor Contactor Overload Relay Temperature • RTD’s embedded at the motor bearings will provide a measured value of the bearing temperature to indicate bearing problems. This temperature feedback can be used to set alarm and shutdown levels. © 2015 Eaton. All Rights Reserved. 32

Motor Protection Relay Comparison Feature Bi-Metallic Basic Solid State Advanced Solid State Thermal Overload X X X Phase Loss X X X Ground Fault X X Phase Imbalance X X Motor Jam X Over/Under Voltage X Power Up Delay X Phase Rotation X Over/Under Power X Thermistor or RTD X Alarms X Communications X © 2015 Eaton. All Rights Reserved. 33

Performance Motor Protection Relay Value Map Advanced Solid State Basic Solid State Bi-Metallic Price © 2015 Eaton. All Rights Reserved. 34

Selecting a Motor Protection Relay • Critical Load? • Lost production and revenue • Safety system • Quality of life • Performance vs Price. • Process Up-time Requirement. • Fault based maintenance • Time based preventative maintenance • Predictive based preventative maintenance © 2015 Eaton. All Rights Reserved. 35

Motor Protection Enhancements • Motor Management Systems • Protection • Monitoring • Control • Motor efficiency monitoring. • Motor condition (wellness) monitoring. © 2015 Eaton. All Rights Reserved. 36

© 2015 Eaton. All Rights Reserved. 37