Why Did My DC Motor Fail Under Load?

Click For Summary

Discussion Overview

The discussion centers around the failure of a DC motor under load while operating a conveyor system. Participants explore potential causes for the motor's inability to run under load, including electrical supply issues, mechanical failures, and field coil problems. The conversation includes technical details about the motor's specifications and performance characteristics.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that the motor shows high current (130 A) at a low voltage (30 V) and questions whether the electrical supply can maintain adequate voltage under load.
  • Another participant suggests that the motor has been operating satisfactorily until now and raises the possibility of a short in the field coil affecting torque, proposing a method to check for this issue using temperature monitoring.
  • There is a discussion about the rated armature current (225 A) and the implications of the motor consuming high current when stalled or under low voltage conditions.
  • One participant mentions that an open field condition could lead to high armature current with virtually no torque, prompting a question about whether the motor has a series or shunt field configuration.
  • Clarifications are made regarding the motor's configuration, confirming it is a series field motor.
  • Participants inquire about the type of power supply being used to power the motor, indicating that this may be a critical factor in diagnosing the issue.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the causes of the motor's failure under load. There is no consensus on the exact issue, with various hypotheses being proposed and explored.

Contextual Notes

Some limitations include the lack of detailed information about the power supply and the specific methods used to check the field coil. Additionally, the discussion does not resolve the uncertainty surrounding the motor's performance characteristics under load.

Who May Find This Useful

Individuals interested in troubleshooting DC motors, particularly in industrial applications, may find this discussion relevant.

leendabests
Messages
3
Reaction score
0
Hello,

Im using DC motor to run the conveyor but suddenly the armature shows high current 130 A for 30 V power and the speed can't increase anymore. The motor power stated in the name plate is 93.8 KW, Armature voltage is 453 V and Armature ampere is 225 A. The motor can run free load after disconnected from the load but fail to run on load. We have checked the field coil, armature coil and the brushes . The are no insulation damaged since it can be run free load.

What are the possible causes to the motor that fail to run on load? Is it because not strong magnetism or another mechanical failure?
 
Engineering news on Phys.org
sounds to me like the electrical supply is not stout enough to maintain voltage when it's loaded to as little as 30 amps.
130 volts at 30 amps is how many watts?
How many watts does the conveyor require?
Can the motor deliver more watts out of its shaft than it receives in the wires from its supply?
What do you have powering this motor?

old jim
 
It is 30 V 130 A... The actual armature voltage is 453 V. But when the voltage reaching only 30 V the armature current already 130 A. The the armature stop to rotate.
 
leendabests said:
Im using DC motor to run the conveyor but suddenly the armature shows high current 130 A for 30 V power and the speed can't increase anymore.
This is a motor that has been operating satisfactorily in this task for a long time? Then suddenly it has stopped turning under load, and you have made no changes in the motor's controller nor the conveyor?

How did you check the field coil? I'm thinking that a short in the field would still show continuity, yet give a major reduction in torque. How to reveal this? Maybe if you could give it rated field current, and as it warms up use an infrared camera to monitor the temperature of the outside casing, you might find an ominously cool area indicating no heating underneath.
 
The rated armature current is 225A. Why are you stopping at 130A (at 30V)?? Keep increasing the voltage until you get 225A, if that don't give you enough speed (or any speed at all) then we can say something is wrong.
Its normal for DC motor to consume large current when stalled or during starting. It is also normal for it to consume rather large* current when applied with rather small voltage than rated, because this results in not enough power being developed and motor either refuse to starts or rotates very slowly.
*large in the sense of ratio of Applied Voltage/Current.
 
300px-Carbon_brushes.jpg



Just sayin'
 
an open field results in high armature current and virtually no torque.

is it series or shunt field?
 
The voltage stopped at 30 V only and can not increase anymore. And the current showed 130 A at that time.. The motor is in series field.
 
leendabests said:
The voltage stopped at 30 V only and can not increase anymore. And the current showed 130 A at that time.. The motor is in series field.

Can you please give some details of what type of supply is being used to power the motor.
 

Similar threads

Superconducting motor thought experiment/ questions
  • · Replies 1 ·
Replies
1
Views
2K
What could be causing heavy sparking on load for this DC motor?
  • · Replies 1 ·
Replies
1
Views
8K
Why is my homemade DC motor not working?
  • · Replies 10 ·
Replies
10
Views
5K
Engineering Electrical Machine - Shunt DC Motor Problem
  • · Replies 41 ·
2
Replies
41
Views
7K
Engineering Electrical Machines DC Shunt Motor
  • · Replies 16 ·
Replies
16
Views
4K
Troubleshooting Brushed DC Motor Health: Insights from an Automotive Technician
  • · Replies 5 ·
Replies
5
Views
6K
12v dc motor speed self limited?
  • · Replies 1 ·
Replies
1
Views
3K
Engineering Can DC Geared Motors Be Used as Generators?
  • · Replies 5 ·
Replies
5
Views
3K
What Is Back EMF in DC Motors and How Does It Affect Performance?
  • · Replies 3 ·
Replies
3
Views
4K
Should DC operated oil rigs convert to AC?
  • · Replies 1 ·
Replies
1
Views
13K