Malfunctioning ‘motor controller’ caused fire in BRT buses: report

PESHAWAR: The recent fire incidents in the Peshawar Bus Rapid Transit buses were caused by the malfunctioning of a motor controller installed between hybrid batteries and electrical motors, reveals a month long inspection of the vehicles.

The BRT service formally launched on Aug 13 has been suspended since Sept 16 after fire broke out in four buses.

A 20-member team of the Chinese bus maker, Xiamen Golden Dragon, had come to Peshawar last month to detect the cause of fire.

In a report submitted to the TransPeshawar, the operator of bus service, the company has noted that the motor control unit (MCU) acted as the core of the hybrid systems in buses and it was managed by a programme developed according to input of external conditions.

Manufacturer plans to redesign those controllers, install temperature sensors

It said normally, the ripple current generated by the DC-AC conversion of current flows was either absorbed by batteries or smoothed via capacitors in motor controller.

The company, however, said the failure of capacitors to perform that task led to the short-circuiting of high-volt power circuit and eruption of fires in buses.

It said the peak current was supposed to be restrained by software update to limit the flow of the current from the motor controller change but certain electronic components in bus MCUs were damaged by the abnormal current before the software update and therefore, accidents occurred.

The company said it would address the issue by redesigning and replacing bus motor controllers.

It also said the insulated gate bipolar transistor in the motor controller would be changed to reserve larger power capacity and improve the performance of the temperature resistance and the current conversion efficiency.

In the report, the company said temperature sensors would be installed in motor controllers to record and issue warning for any abnormal temperature in the unit. It said for 12 meters long buses, single motor controller would be changed to dual one.

An audit by the Auditor General of Pakistan last year had found out that the delivery of 51 buses more than a year before the completion of civil works due to political consideration caused depreciation of hybrid batteries and led to losses of Rs5 million until June 2019.

The AGP said any further delay in the resumption of operation would further increase the loss due to the depreciation of batteries.