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CUSTOMER CARE COMMITMENT

When electrical power fails, it’s no small matter. Repairs must be made as quickly as possible. That’s where M&R Electric Motor Service excels. Fast turn arounds are our business. Motors such as the one pictured here have been rewound quickly and efficiently for our customers. 

 

Dynamic Balancing Of Shafts And Rotors.


Digital Surge Testing

Surge testing of A/C electric motors and generator windings displays a accurate picture of the winding and insulation conditions. Tests made can determine good, marginal or defective windings and the winding insulation before a major failure occurs. In many cases actions can be taken to head off these failures, preventing costly delays and repairs. This digital surge tester applies a predetermined voltage and captures a sinusoidal wave form for each phase of the unit under going the test. It also displays megohms and Hi-Pot measurements. All the information is used to make the correct decision on what repairs are needed.


This is a Surge Test:

The wave form showing a good winding. You will notice how each of the three phases overlap each other. Representing what appears to be only one wave line. Pictured is the windings that are being tested, no faults are present.


Turn to Turn / Phase to Phase Weakness:

If there is a Turn to Turn / Phase to Phase weakness The wave patterns will separate and appear unstable This is an indication of imminent failure. The motor should be serviced immediately. Pictured is a turn to Turn / phase to phase fault.


Ground Faults:

If there is weak insulation the wave pattern will indicate the weakness. If a motor with a turn to turn fault short stays in service circulating currents may produce hot spots and the ground wall insulation will eventually burn up causing a shut down. Pictured is a ground fault.


 

Trouble Shooting Chart

 
 
 
Failure Probable Cause Corrective Measures
Motor Fails to Start
  1. No voltage supply
  2. Low voltage supply
  3. Wrong control connections
  4. Loose connection at some terminal lug
  5. Overload
  6. Brushes
  • Check feed connections to control system and from this to motor
  • Check voltage supply and ascertain that voltage remains within 10% of the rated voltage shown on the motor nameplate
  • Compare connections with the wiring diagram on the motor nameplate
  • Tighten all connections
  • Try to start motor under no-load conditions. If it starts, there may be an overload condition or a blocking of the starting mechanism. Reduce load to rated load level and increase torque.
  • Brushes may be worn, dirty or incorrectly fitted.
High Noise Level
  1. Unbalance
  2. Distorted shaft
  3. Incorrect alignment
  4. Uneven air gap
  5. Dirt in the air gap
  6. Extraneous matter stuck between fan and motor casing
  7. Loose motor foundation
  8. Worn bearing.
  • Vibrations can be eliminated by balancing rotor. If load is coupled directly to motor shaft, the load can be unbalanced.
  • Shaft can be bent, check rotor balance and eccentricity
  • Check motor alignment with machine running
  • Check shaft for warping or bearing wear
  • Dismantle motor and remove dirt or dust with jet of dry air
  • Dismantle motor and clean. Remove trash or debris from motor vicinity
  • Tighten all foundation studs. If necessary, realign motor
  • Check lubrication. Replace bearing if noise is excessive and continuous
Overheating of Bearings
  1. Excessive grease
  2. Excessive axial or radial strain on belt
  3. Deformed shaft
  4. Rough bearing surface
  5. Loose or poorly fitted motor end shields
  6. Lack of grease
  7. Hardened grease causing locking of balls
  8. Foreign material in grease
  • Remove grease bleeder plug and run motor until excess grease is expelled
  • Reduce belt tension
  • Have shaft straightened and check rotor balance
  • Replace bearings before they damage shaft
  • Check end shields for close fit around circumference and tightness
  • Add grease to bearing
  • Replace bearings
  • Flush out housings and relubricate.
Intense Bearing Vibration
  1. Unbalanced rotor
  2. Dirty or worn bearing
  3. Bearing rings too tight on shaft and /or bearing housing
  4. Extraneous solid particles in bearing
  • Balance rotor statically and dynamically.
  • If bearing rings are in perfect condition, clean and relubricate the bearing, otherwise, replace bearing.
  • Before altering shaft or housing dimensions, it is advisable to ascertain that bearing dimensions correspond to manufacturer's specification
  • Take bearing apart and clean. Reassemble only if rotating and support surfaces are unharmed.
Overheating of Motor
  1. Obstructed cooling system
  2. Overload
  3. Incorrect voltages and frequencies
  4. Frequent inversion
  5. Rotor dragging on stator
  6. Unbalanced electrical load (burnt fuse, incorrect control)
  • Clean and dry motor; inspect air vents and windings periodically
  • Check application, measuring voltage and current under normal running conditions
  • Compare values on motor nameplate with those of mains supply. Also check voltage at motor terminals under full load.
  • Exchange motor for another that meets needs.
  • Check bearing wear and shaft curvature.
  • Check for unbalanced voltages or operation under single-phase condition.