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一般故障と対策Uシリーズ

General Troubleshooting U seriesSシリーズはこちら

If the hoist has been used under unfavorable working condition, handled roughly or become old, like general machines, it shows various troubles and nonconformities.
All troubles and nonconformities cannot be described here. General troubles are listed below for your reference.
Most of troubles not listed below are caused special factors. Regarding such troubles, consult the nearest distributor or Mitsubishi Electric Hoist Corporation.

Problem Cause Remedy
1

Touching the hoist or pushbutton pendant causes an electric shock.

(1)I-beam or pushbutton pendant metallic casing grounding failure

(1)Ground completely.
100Ω or less at 200 V

   

(2)Adhesion of paint to the I-beam surface
Leakage current increases due to high-frequency component of inverter output voltage. The rated sensitivity current of the earth-leakage circuit breaker shall be 100 mA or more to prevent unnecessary operations.
The circuit breaker is designed nor for prevention of electrical shocks, but for prevention of a fire caused by electrical leakage. For this reason, remedies (1), (2), and (5) described on the right side should be observed.

(2)Use the hoist suitable for the ambient conditions (waterproof type, etc.).
Remove paint completely.

   

(3)Hoist or pushbutton pendant insulation failure

(3)Check, and repair.

   

(4)Current leaking from other equipment or wiring reaches the hoist through the I-beam.

(4)Check, and repair.

   

(5)The floor conductivity is high.
•The floor is wet with a highly conductive liquid, such as water.
•The hoist is on a highly conductive surface, such as an iron plate, steel structure and surface plate.

(5)Install the hoist on a floor with low conductivity, such as a dry concrete floor.

2

Operation in reverse direction to that indicated on pushbutton.

(1)Incorrect connection of power supply line
(If the commercial power is used for traversing operation)
Even if the power line is not connected correctly, operation will not be performed in the opposite direction.

(1)Exchange the phases R and T of the power supply.

   

(2)Wire rope wound reversely.

(2)Wind the rope correctly.

3

Wire rope wears badly.

(1)The rope wears soon because it is frequently pulled laterally and vertically.

(2)Disordered winding

(3)Use of wire rope other than parallel stranded rope

(4)Wire rope oil not applied.

(1)Correct the using method.

(2)See Item 4.

(3)Replace the wire rope with a proper one.

(4)Apply oil.

4

Wire rope is wound ununiformly.

(1)Pulling laterally and vertically at too large angles (Less than 10° for pulling laterally or less than 3° for pulling vertically)

(1)Correct the using method.

   

(2)Wire rope distorted

(2)Replace.

5

The 2nd-stage limit switch operates.

(1)Incorrect connection of power supply line

(1)Exchange the phases R and T of the power supply.

   

(2)Wire rope wound reversely

(2)Set the upper limit correctly.

   

(3)Although the use of the no-load high-speed function has been specified, the upper limit stop point has not been set. Or the upper limit set position is too high.

(3)Set the upper limit to the proper position.

6

Wire rope is cut.

(1)The rope catches on something during hoisting.

(2)Corrosion due to chemicals

(3)Use of badly worn wire rope

(1)Handle and maintain the rope properly. Replace the defective wire rope.
(Use the Mitsubishi genuine wire rope.)

7

The hoist does not start even if the push¬button is pressed.

(1)Pushbutton defective, or pushbutton cable broken

(2)Incorrect wiring of power switch, fuse, contactor, or pushbutton, imperfect contact of trolley line, loose screws, etc.

(3)The inverter does not give 3-phase output.

(4)No signal is returned from the sensor, or one of the rotation signals (signals for 2 phases) is not returned from the RRS board.

(5)The hoisting motor torque is insufficient for overload, and the hoist stops.

(6)The hoisting motor overheats due to too frequent use, the torque drops, and the hoist stops.

(1)Repair, replace, or cut out.

(2)Check, and repair. See the expanded connection diagram.

(3)Check the inverter.

(4)Check and replace the RRS board. Check the signal line (microphone cord) for dis-connection.

(5)Reduce the load.

(6)Use the hoist at appropr¬iate intervals.

8

The hoist lowers and stops during hoisting

(1)Overload

(2)Hoisting motor overheat

(3)Hoisting motor wire breakage

(1)Reduce the load.

(2)Use the hoist at appropriate intervals.

(3)Check, and repair.

9

The hoist stops suddenly during hoisting.

(1)Inverter trip due to overvoltage caused by hoisting an overload.

(2)Inverter overvoltage tripping is caused due to rise in the resistance value that is caused by temperature rise of the discharging resistor due to too frequent use.

(3)Disconnection of discharging resistor

(1)Reduce the load.

(2)Use the hoist at appropr¬iate intervals.

(3)Check, and repair.

10

Power is applied to the traversing motor, but the motor growls and takes a longer time (2 sec. or more) to start.

(1)Electric resistance is high due to wiring, switch or trolley contact failure or loosened screws. (Voltage drop at start)

(2)Wires too thin or long

(3)Supply voltage too low.

(4)Electromagnetic brake not released.

(5)Defective electromagnetic brake coil.

(1)Check, and repair.

(2)Change the wiring in accordance with the selection table.

(3)Change the transformer taps.

(4)See Item 14.

(5)Replace the coil.

11

The hoist suddenly stops during lifting or lowering operation.

(1)The 1st-stage limit switch functions.

(2)Inverter trip due to too low supply voltage

(3)Hoisting brake works.

(4)Inverter trip due to overload or ground lifting

(5)Fall caused by overload is detected.

(6)Malfunction due to noise.

(1)Lower the load.

(2)Change the transformer taps.

(3)See Item 14.

(4)Re-examine the lowering method and load.

(5)Re-examine the lowering method and load.

(6)Fit a noise filter to the 3-phase power supply.

12

The motor overheats

(1)Inching operation is performed too frequently.

(2)Electromagnetic brake not released.

(3)Operating time long

(4)Overload.

(1)Apply a special design.

(2)See Item 13.

(3)Adopt the same remedies as Item 10, or do not use the motor too frequently.

(4)Reduce the load.

13

Pressing a pushbutton rattles the contactor.

(1)Extreme voltage drop

(1)Refer to Item 10.

14

The relay functions, but the electro¬magnetic brake is not released.
The electromagnet will not attract.

(1)Too large voltage drop, or too low supply voltage

(2)Too large core gap

(3)No gap, or gap adjusted too large.

(4)Movable parts catch on something.

(5)Brake circuit cable broken, or screws loosened.

(6)Brake circuit diode (DC) defective

(7)Coil burnt out.

(8)Too large center clearance

(1)See Items 10 and 11.

(2)Replace the brake disk.

(3)Re-adjust.

(4)Repair.

(5)Check, and repair.

(6)Replace the diode assembly.

(7)See Item 15.

(8)Correct.

15

The electromagnetic brake coil has been burnt out.

(1)High frequency of uses

(1)Correct the operation method, and replace the coil.

16

The electromagnetic brake does not work effectively.

(1)Too large core gap

(1)Replace the brake disk.

   

(2)The relay does not function properly.

(2)Replace the relay.

   

(3)The electromagnetic contactor cannot properly cut off the power.

(3)Check the internal wiring.

   

(4)Adhesion of oil to the brake disk

(4)Degrease the brake disk, or replace the brake disk.

   

(5)The immediate cut-off contactor does not operate properly. (Direct current)

(5)Replace the contactor.

17

The traversing brake is too effective or ineffective.

(1)Brake adjustment failure

(1)Adjust the brake properly with the adjusting bolt.

18

Rotation with the traversing brake applied.

(1)Brake coil wire breakage, or mis-connection

(2)Diode defective, or mis-connection

(3)Too small or large gap

・Replace, or repair.

19

The traversing motor does not have enough rotation power, or will not function.

(1)Brake coil wire breakage, or mis-connection

(2)Diode defective, or mis-connection

(3)Too small or large gap

・Replace, or repair.

20

The gears make too loud noise.

(1)Gears and bearings worn out

(1)Replace.

21

Traversing wheels spin.

(1)The traversing wheel on the driving side is lifted due to the inclined I-beam.

(2)Paint, oil, or dust is on the transfer surface of the I-beam.

(1)Install the hoist in the reverse direction.

(2)Clean, or, if necessary, grind.

22

The trolley wheels are easily dis¬connected.

(1)The trolley wire has not been stretched as specified.

(2)The trolley pole has been installed in the reverse direction.

(3)Wheels not on the same level

・Improve.

23

The overload alarm does not function properly.

・The power supply line is not correctly connected to the board.

・Correctly connect the power supply line. Connect “1” and “S” to “A” and “B” on the board.

24

The pushbutton will not go down smoothly or will not smoothly pop up.

(1)Foreign material caught by inner unit

(2)Defective inner unit

(1)Check or repair.

(2)Replace.

25

Pressing the DOWN pushbutton lowers the load, but pressing the UP pushbutton also lowers the load.

(1)Rotor slippage (The rotor is not properly engaged with the motor shaft.)

(1)Replace.
*In this case, releasing the pushbutton will immediately stop the lowering operation.


Inspection of Power Supply System (Measurement of lowest voltage at start up)

Inspection procedure Judgment and remedy
1

Turn off the power switch to the trolley line.
Connect a voltmeter or electric tester near the insulated shaft of the trolley pole.

・Acceptable if all the three phases are read 400-440 V (up to 480 V for 60 Hz). If not, change the tap connection on the transformer.

・If the readings of the three phases vary, check the transformer wiring.

2

Turn on the trolley line power switch. Read the voltage.

3

Take this measurement between the phases (R-S and S-T).

4

Press the "UP" pushbutton with the voltmeter connected and the power switch on as above.
Due to the high starting current lasting for a moment, the hand on the voltmeter first swings into the low range then swings back into the high range. Read the lowest voltage.

・Acceptable if all the three phases are 360 V or more.

・Can be used if all the three phases are 340 V (60 Hz) or more.
Cannot be used if the voltage is below the above value.
(For a detailed description of the corrective method, refer to Item 10 described in the previous table.)

・If three phases are not balanced, the cause of unbalance is cause (1) of Item 10 described in the previous table. In this case, repair the problem part.

5

Take measure in step 4 above on all the three phases.


(Note)
The voltage readings in step 4 above represent the lowest values when the electromagnet attracts the elements or the motor starts up. Judge the situation based on these voltage readings. When you contact us, please let us know the power supply voltage (see above inspection step 2) and the lowest voltage (see above inspection step 4).

(Instructions for measurement of inverter power supply current)
1.During lowering operation, regenerative energy returns from the hoisting motor to the inverter. This may cause power current not to flow.
2.When lifting/lowering very light load or no load at all, little electric power is consumed. Since power is in this case supplied through two high-voltage power wires, no current may flow through the remaining one wire.
3.During lifting operation, the inverter input current may fluctuate. This is because this current is not sinusoidal.

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