Template:DCMotor CurrentLimit
Current limiting is an advanced, yet easy-to-use feature that intelligently monitors and controls the current through your motor. This will help to keep your system safe in a variety of situations.
The datasheet of your motor will specify the following parameters:
- Rated Current
- Stall Current
We recommend setting your Current Limit to 1.1x the rated current of your motor. For increased performance from your motor, review Surge Current Limit.
You may choose to increase the Current Limit significantly above the rated current of your motor. In these situations, it is important to understand how heat will impact your motor.
The heating of your motor increases with the square of the current through your motor. Below is a table showing the approximate time to failure of a 24VDC motor with a 20A rated current and 100A stall current.
| Operating Voltage (VDC) | Operating Current (A) | Heating Rate | Approximate Time to Failure |
|---|---|---|---|
| 24 | 20 | Normal | N/A |
| 24 | 40 | 4x faster than normal | minutes |
| 24 | 100 | 25x faster than normal | seconds |
Many applications rely on a motor operating at higher-than-rated power levels. This is typically done at a low frequency which allows for adequate heat dissipation. Implementing a Surge Current Limit is one way to easily achieve this.
If your Phidget does not have the Surge Current Limit feature, you may consider dynamically adjusting the Current Limit yourself by monitoring the CurrentInput channel.
Small motors may have a stall current that is less than the minimum Current Limit of your controller. In these situations, your controller will not be able to provide current limiting protection. Consider using a more suitable motor controller or monitor the current yourself via the Current Sensor channel.
Current is directly proportional to torque. If you have an oversized motor that may cause damage to your system downstream, a purposefully reduced Current Limit can provide an extra layer of protection.
Over Temperature conditions may reduce your Current Limit.
