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S series

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General Troubleshooting S series

If the hoist has been used under unfavorable working condition, handled roughly or become old, Various breakdowns and malfunctions will occur,
like general machinery.
Since all breakdowns and malfunctions cannot be described here, General troubles are listed below for your reference.
Most of troubles not listed below are caused by special factors. Regarding such troubles, consult the nearest distributor or Mitsubishi Electric FA Industrial Products 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
(2)Adhesion of paint to the I-beam surface.
(3)Hoist or pushbutton pendant insulation failure
(4)Current leaking from other equipment or wiring reaches the hoist through the I-beam.
(5)The floor conductivity is high.
•The floor is wet with a highly conductive liquid, such as water.
•he hoist is on a highly conductive surface, such as an iron plate, steel structure and surface plate. 		(1)Ground completely.
(2)Use the hoist suitable for the ambient conditions (waterproof type, etc.). Remove paint completely.
(3)Check, and repair.
(4)Check, and repair.
(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.
(2)Wire rope wound reversely. 		(1)Exchange the phases R and T of the power supply.
(2)Wind the wire 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)
(2)Wire rope distorted 		(1)Correct the using method.
(2)Replace.
5 The 2nd-stage limit switch operates. (1)Incorrect connection of power supply line
(2)Wire rope wound reversely
(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. 		(1)Exchange the phases R and T of the power supply.
(2)Wind the wire rope correctly.
(3)Set the upper limit to the proper position.
6 Wire rope is cut. (1)The wire rope catches on something during hoisting.
(2)Corrosion due to chemicals and other.
(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 pushbutton is pressed. (1)Pushbutton cable disconnection
(2)Power switch, fuse, wiring, faulty trolley contact, faulty wiring of contactors and push buttons, and loose screws, etc.
 (1)Replace, or cut out.
(2)Check, and repair.
8 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 is 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.
9 The hoist suddenly stops during lifting or lowering operation. (1)The 1st-stage limit switch functions.
(2)Hoisting brake works.
 (1)Lower the load.
(2)See Item 14.
10 The motor overheats (1)Inching operation is performed too frequently.
(2)Electromagnetic brake is not released.
(3)Long operating time.
(4)Overload. 		(1)Apply a special design.
(2)See Item 14.
(3)Adopt the same remedies as Item 10, or do not use the motor too frequently.
(4)Reduce the load.
11 Pressing a pushbutton rattles the contactor. (1)Extreme voltage drop (1)Refer to Item 13.
12 The relay functions, but the electromagnetic brake is not released.
The electromagnet does 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,etc.
(6)Brake circuit diode (DC) defective
(7)Coil burnt out.
(8)Too large center clearance 		(1)See Items 10(2),(3).
(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.
13 The electromagnetic brake coil has been burnt out. (1)High frequency of uses (1)Correct the operation method, and replace the coil.
14 The electromagnetic brake does not work effectively. (1)Too large core gap
(2)The relay does not function properly.
(3)The electromagnetic contactor cannot properly cut off the power.
(4)Adhesion of oil to the brake disk
(5)The immediate cut-off contactor does not operate properly. (Direct current) 		(1)Replace the brake disk.
(2)Replace the relay.
(3)Check the internal wiring.
(4)Degrease the brake disk, or replace the brake disk.
(5)Replace the contactor.
15 The traversing brake is too effective or ineffective. (1)Brake adjustment failure (1)Adjust the brake properly with the adjusting bolt.
16 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
(4)Adhesion of brakes and linings
 (1)Repair, or replace.
(2)Check, and repair.
(3)Gap adjustment
(4)Check, and repair.
17 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
(4)Adhesion of brakes and linings
 (1)Repair, or replace.
(2)Check, and repair.
(3)Gap adjustment
(4)Check, and repair.
18 The gears make too loud noise. (1)Gears and bearings worn out (1)Replace.
19 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.
20 The trolley wheels are easily disconnected. (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.
21 The overload alarm does not function properly. (1)The power supply line is not correctly connected to the board. (1)Correctly connect the power supply line. Connect “1” and “S” to “A” and “B” on the board.
22 The push button cannot be pressed smoothly or does not return. (1)Internal unit gets caught due to intrusion of dirt, etc.
(2)Internal unit failure
 (1)Check and repair.
(2)Replace.
23 Pressing the DOWN pushbutton lowers the load, but pressing the UP pushbutton also lowers the load. (1)Rotor idling (motor shaft fit loose) (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 200-220 V (up to 240 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 180 V or more.
  • Can be used if all the three phases are 170 V (60 Hz) or 160 V (50 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.