Overhead Crane Electrical System Failures and Repair: Electrical Equipment, Electrical Control and Circuit

January 11, 2025

Overhead cranes are widely used in industrial settings, and the failures and repairs of overhead crane electrical systems are of critical importance. The performance of these systems is directly tied to the safety and efficiency of crane operations. This article will explore the common causes of overhead crane electrical system failures and repair methods. By understanding these issues, operators can better prevent and address potential problems, ensuring stable equipment operation and smooth production processes.

Overhead Crane Electrical Equipment Failures and Repair

This section covers the failures and repairs of AC motors, AC electromagnets, AC contactors, and relays.

1. AC Motor Failures and Repair

Failures	Causes	Repair
Evenly overheating the whole motor	JC% is too big, causing an overload	Lower working duty or change high JC% motor
	Working at low-voltage	Stop working when the working voltage is 10% lower than the rated voltage
	Motor selection is not the right	Select the right motor
	Crane parameters changed after checking	Check and adjust to ensure the specification
Local overheating of stator	Silicon-steel plate is short-circuited	Use insulation paint to the places where short circuits happened
Local overheating of the stator winding	Wiring fault	Check and eliminate the wrong wiring
Local overheating of the stator winding	2 points on winding have a short circuit with a shell	Repair winding of phase
Temperature of rotor raise, heavy current impact stator, motor cannot get full speed at rated current.	End winding terminals, neutrality points and parallel winding get poor contact	Check welds and eliminate defects
	Winding group and sliding loops have a loose connection	Check connection condiction
	Dynamo brushes have a loose connection	Check and adjust brushes
	Poor contact in the rotator circuit	Check loose and contact condition poor and rectify. Check the resistance and change the broken one.
Motor vibration when working	Motor and reducer axes are not on the same line	Re-install
	Bearing damage and wear	Replace bearing
	Deformation of rotor	Check
Abnormal noise when working	A phase of stator error	Check wiring and modify
	In the stator iron core is not pressed	Check stator and repair
	Bearing wear	Replace bearing
	Wedge expands	Cut expanded part or replace wedge
After the motor is loaded, its rotation speed slows down	Ends of rotator short circuit or 2 earthing locations of rotor winding	Eliminate short circuits and check each loop, repair the damaged and eliminate short circuits
The friction of the stator and rotator when the motor is working	The end of the bearing connection is short-circuited	Replace the damaged bearing and check the cover position, eliminate the rag on the stator and rotor
	The loop connection is not right, flux is not balanced	Make a connection right and check if each phase is equal in the stator
Spark on brush or sliding ring is burned	Brush bad grinding	Grind brush
	The brush is too loose when working	Adjust brush or grinding properly
	Brush or loop dirty	Clean with alcohol
	The loop is not flat, causing brush jumping	Machining and grinding loop
	Low pressure of brush	Adjust brush pressure (18-20KPa)
	The brush grade is wrong	Replace
	The current distribution of brush is not even	Check power-feeding the wire and brush, and adjust
Sliding ring open circuit	Loop and brush dirty	Clean dirt

AC Motor Failures and Repair

2. AC Electric Magnet Failures and Repair

Failures	Causes	Repair
Overheat of loop	Overload of magnetic iron force	Adjust the spring pulling force
	The fixed part and stationary part of the closed circuit have a gap	Eliminate gap
	Loop voltage and power voltage do not match	Replace loop or change connection method
Too noisy when working	Magnetic iron overload	Adjust the spring
	Dirt on the magnetic flow circuit surface	Clean dirt
	Deflection of magnetic system	Adjust mechanical part of brake and eliminate deflection
Unable to overcome the spring force	Magnetic iron overload	Adjust the main spring of break
	Spring force is too big	Adjust the main spring of break
	Low voltage	Stop working

AC Electric Magnet Failures and Repair

3. AC Contactor and Relay Failures and Repair

Failures	Causes	Repair
Overheat of loop	Loop overload	Reduce the pressure that the movable terminal acts on the fixed terminal
Overheat of loop	Magnetic flow movable part cannot come into contact with fixed part	Eliminate deflection jamming, dirt or change loop
Contact too noisy	Loop overload, dirt on magnetic flow surface	Reducer contact pressure, clean dirty
Contact too noisy	Magnetic flow self-adjust system jamming	Eliminate jam
Contact overheat or burned	Contact lacks of pressure	Adjust pressure
Contact overheat or burned	Contact is dirty	Clean or replace
Main contact cannot connect	Switch not close, EM switch not close	Close switch
	Upper door switch not close	Close switch
	Control stick is not at 0 position	Put lever to 0 position
	Control circuit fuse burned	Check or replace fuse
	No power in circuit	Check if voltage is on
Power-off protection happens frequently	Contact pressure is not enough	Adjust contact pressure
	Contact burned	Replace or grind contact
	Contact is not clean	Clean
	Working overload, over current	Reduce current load
	Slide wire is not parallel, loose contact between current collector and slide wire	Adjust the rail or wire
Contact too slow	Clearance of magnet pole surface is too large	Shorten pole surface clearance
Contact too slow	Upper part of base plate is more protruding than lower part	Install parts vertically

AC Contactor and Relay Failures and Repair

Overhead Crane Electrical Control and Circuit Failures and Repair

Failures	Causes	Repair
Fuse in control circuit burned after knife switch closed	This phase earthing in control circuit	Check earthing part by ohmmeter and eliminate malfunction
After mechanism transmission, over current relay still work	Setting value of over current relay cannot meet requirements	Adjust relay as following formula: I(rated)= ( 2.25~2.5 ) I(rated)
After mechanism transmission, over current relay still work	Mechanical transmission part jammed leading to motor overload	Check transmission part and eliminate jam
Motor cannot rotate after controller is closed	When one phase is lost, the motor emits a noise	Find damage and rewiring
	Wire breakage in rotator circuit	Find damage and rewiring
	Loop has no voltage	Find damage and rewiring
	Contacts in controller cannot contact	Repair controller
	Current collector brash failure	Repair brush of collector
	Brake malfunctions and cannot release	Repair brake
Motor can only rotate in one direction after controller is closed	Reverse contact loose connection or malfunction with steering mechanism	Check controller and adjust contact terminal
	Power distribution line failure	Use the short-circuit method to locate and eliminate the fault
	The mechanism moved to its limit and triggered the limit switch	When it can only operate in one direction, troubleshoot and fix the fault
	The limit switch has malfunctioned	Inspect the limit switch and eliminate the fault
After the terminal limit switch is activated, the main contactor does not release	A short circuit has occurred in the end switch circuit	Perform maintenance and eliminate the short circuit
	The wires are incorrectly connected to the controller	Correct the wiring errors
The controller experiences jamming and impact during operation	The positioning mechanism has malfunctioned	Eliminate fault
	Contact jam in curve chamber	Adjust contact position
The controller cannot pull during operation	Positioning mechanism malfunction	Adjust pressure
The controller cannot pull during operation	Contactors burning and bonding	Clean contactor
The generator is not excited	The excitation circuit is disconnected	Inspect the excitation circuit
The generator is not excited	Reverse rotation of generator	Replace 2 phase wiring of the driving motor
After disconnecting power (control circuit break) the contactor of protection box won’t break-off	There is grounding or a short circuit in the control circuit	Find those places and solve problems
	Weld contact terminal,give power supply to main circuit	Cut burned contact terminal to make it function again

Overhead Crane Electrical Control and Circuit Failures and Repair

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Cindy

WhatsApp: +86-19137386654

Email: cindywang@hndfcrane.com

I am Cindy, with 10 years of working experience in the crane industry and accumulated a wealth of professional knowledge. I have chosen the satisfying cranes for 500+ customers. If you have any needs or questions about cranes, please feel free to contact me, I will use my expertise and practical experience to help you solve the problem!

TAGS: overhead crane electrical system,overhead crane failures,overhead crane repair

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Overhead Crane Electrical System Failures and Repair: Electrical Equipment, Electrical Control and Circuit

Table of Contents

Overhead Crane Electrical Equipment Failures and Repair

1. AC Motor Failures and Repair

2. AC Electric Magnet Failures and Repair

3. AC Contactor and Relay Failures and Repair

Overhead Crane Electrical Control and Circuit Failures and Repair

PDF Download

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