What are Some Common Malfunctions of Mitsubishi Elevators?

Mitsubishi GPS series elevators have a mature design and a stable Mitsubishi control system. With proper maintenance, the failure rate is very low, and fault codes are easily accessible, making it straightforward to identify the cause of a malfunction. However, if negligence occurs, it can be difficult to find the cause when a fault does occur. In years of maintaining GPS elevators, the following representative faults have been handled and are summarized below for reference:

1. Insufficient travel of the brake core

Fault Phenomenon: 

A GPS-equipped elevator, imported from GPS-2, which has been in operation for 8 years, experiences irregular, sudden stops. These stops are not frequent, but the elevator automatically levels itself, opens the door, and continues operating after the error. The fault code given on the Mitsubishi Elevator board is EA, indicating a brake fault. However, the brake's opening and closing are normal, its resistance value is normal (80-90 ohms), and the brake voltage is also normal.

Analysis and Solution: 
Initially, it was determined that the problem was not with the Mitsubishi Elevator control cabinet, as this would occur frequently. Inspection of the brake revealed that its contact gap was too small, only 1.0mm, while the normal gap should be 2+0.5mm. Then, the brake core of Mitsubishi Elevator parts was disassembled, and it was found that due to years of neglect, oil had accumulated inside the core cavity, causing insufficient core travel and poor extension/retraction. 
When energized, the electromagnetic force could not reach its maximum value. When external voltage fluctuated or other factors occurred, the core contracted, causing the brake contacts to engage and resulting in the malfunction. After thoroughly cleaning the core and cavity, the core travel was readjusted to 1.5mm, and the brake gap was opened to 2.5mm. The malfunction no longer occurred.

The Mitsubishi Elevator brake core should be maintained regularly, at least once every 3 months. The brake and its contacts should be adjusted according to specifications and checked frequently. In this case, the oil contamination caused an insufficient magnetic force generated by the coil to balance the brake spring force, causing the brake contacts to engage momentarily, transmitting an error message to the main board, and the elevator to stop abruptly.

2. Fault Caused by Guide Shoe Deformation

Fault Phenomenon: 

An imported GPS-I elevator, which had been in operation for 7 years with very few Mitsubishi elevator malfunctions, experienced an abrupt stop near the top floor after guide shoe wear and replacement. It then slowed down and leveled off. Operation outside the top floor was problem-free, and the P1 board showed no error.

Analysis and Solution: 
The problem is definitely related to the top-floor equipment. Since the elevator hasn't reached the leveling position, limit switches and over-limit switches are not considered initially. First, the 1USD and USR switches are checked. They engage normally manually. The distance between the guide shoe and the switch is 62mm (standard is 58±2mm), which is too large. Running at slow speed through 1USD and USR, the voltage between 1USD, USR, and 420V is measured with a multimeter. The 48V voltage disappears at the switch activation point, indicating normal operation. 
However, during high-speed operation, the voltage momentarily appears when the guide shoe sweeps across USR. This proves that the USR activates at high speed, but the signal disappears momentarily, causing the abrupt stop. 
A detailed inspection of the entire impact bow revealed a 30mm long dent in the middle, bent inwards by 10mm, likely due to pressure during installation. The Mitsubishi lift switch roller exhibited momentary jumping when running over this dent. After correcting the deformation of the impact bow and adjusting the distance between it and the switch to 56mm, the fault disappeared.

Different elevator types have different design philosophies. The above-mentioned fault was caused by a loss of voltage in a critical circuit 420C of the group control section, which triggered the NS (No Service) function, causing all elevators to fail to operate. If you are not familiar with its characteristics, you will not be able to solve the problem by checking the faults of individual units.

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