# Brushless DC motor values at voltage other than nominal

I am currently using a maxon three phase BLDC motor (datasheet PN:412825) that is rated for 48 volts (see spec sheet below). I am running the motor at 18.5 volts (requirement for my application). I am in the process of tuning the controller, and the application is asking me to enter some values such as peak current and continuous stall current.

As far as motor characteristics, I believe these are constant and are irrelevant to changes in voltage (correct me if I am wrong). For the values such as stall current and nominal current, I'm assuming these are dependent to the system voltage.

My question is: Can I just take the values from the datasheet, or do I have to calculate or obtain them from an experiment? If so what are the steps to obtaining these new values. As far as motor characteristics, I believe these are constant and are irrelevant to changes in voltage. [...] For the values such as stall current and nominal current, I'm assuming these are dependent to the system voltage.

The stall current / peak current / starting current are the same and they are defined by the maximum applied voltage divided by the terminal resistance.

It depends on what the application is doing with it.

Stall current is the current that flows through the motor at the rated voltage (note that 43.8V is roughly equal to 48V/1.1 ohms).

If your application is using the stall current plus the supply voltage of 18.5V to calculate the motor resistance, then it'll get a wrong answer.

Not knowing the innards of your application, I can't tell you. You may want to dig in the documentation and see what they're using the stall current for, and if it's to get the resistance (which lesser motor datasheets sometimes leave out) see if you can just enter that.

The stall current will vary according to $$\I_{stall}=\dfrac{V_{supply}}{R_{terminal}}\$$, but the nominal current is unchanged, as it is the current that can continuously flow through the winding without creating excess heat.

When changing voltage supply, the affected parameters are: