# What capacitor to use for motor to stop the power supply from tripping every second

Joined Apr 15, 2022
2
Hi I have a motor of 24V and 180W power and when I add load to it runs but the power supply keep switching on and off so i think more power supply is required but i am already providing 10Amps and 24V so i thought I could use a capacitor. Am I right in my assumption? And if yes how do I calculate the capacitor value?

#### AlbertHall

Joined Jun 4, 2014
12,202

The motor, at start up, likely draws a lot more current than the 180W would suggest and so trips the supply protection system.
You could use a supply capable of a greater current. You could measure the resistance of the motor and so calculate the maximum current required by the motor (24V/motor resistance).
If you don't need the motor to start up quickly you could possibly use a NTC surge limiter to limit the initial current drawn by the motor.

#### KeithWalker

Joined Jul 10, 2017
2,727
A capacitor will not help. If you are supplying 10A at 24V to your motor, that is 240W. If your motor is rated at 180W, you are overloading it and it will not last too long.What is your supply rated for?. The answer is that you probably need a a more powerful motor and power supply.

Joined Apr 15, 2022
2

The motor, at start up, likely draws a lot more current than the 180W would suggest and so trips the supply protection system.
You could use a supply capable of a greater current. You could measure the resistance of the motor and so calculate the maximum current required by the motor (24V/motor resistance).
If you don't need the motor to start up quickly you could possibly use a NTC surge limiter to limit the initial current drawn by the motor.
What value of the NTC surge limiter should I use

Joined Jul 18, 2013
26,712
Are you using a SMPS to operate the motor?
If so, these are proven very unreliable for this application.
A linear supply is much more suitable.

#### PatrickMalarkey

Joined Oct 2, 2021
120
Hi I have a motor of 24V and 180W power and when I add load to it runs but the power supply keep switching on and off so i think more power supply is required but i am already providing 10Amps and 24V so i thought I could use a capacitor. Am I right in my assumption? And if yes how do I calculate the capacitor value?

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#### PatrickMalarkey

Joined Oct 2, 2021
120
Stormtracker: As a second thought, if you're using a DC motor, there is a charging/discharging of individual electromagnets comprising the armature and field magnets in a DC motor, but to reduce current through a DC motor with a capacitor, the capacitor needs to be operating as an AC element. My best advice is to either consider that specific motor defective or buy a larger amperage supply. Or one of other method to re-route the inductive kickback of the armature and field magnet arrangement. And I've never done that, but it's quite easy. You need about 5 to 10 diodes with a current rating total of over the amperage you'd estimate your motor uses; and wire them to oppose current flow though to hem from the power source (in other wards the supply). Your motor may or may not drop it's kickback current though itself while at the same time oppose the supply voltage, this limiting current draw by your motor. Maybe, but? Also, how many volts does your supply put out? You might be trying to run a 24 volts motor on a 120 volt supply, in which case get yourself a 24 volts supply with an appropriate AC/DC output.

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Joined Jul 18, 2013
26,712
individual electromagnets comprising the armature and field magnets in a DC motor,
Very rare to find wound fields in DC motors for quite some time now.
All PM generally.

#### MrSalts

Joined Apr 2, 2020
2,767
Let's say your motor is drawing 10A normally and 10 A more to start under load. Assume the motor take a half-second to get up to speed and you want the suplly to stay above 90% voltage supply (21V).

You would need a capacitor bank between 1 and 2 Farads. That much capacitance would likely pop your power supply before it gets fully charged - without even connecting the motor. Easiest to get a power supply with more heft.

Joined Jul 18, 2013
26,712
....... A power supply consisting of a suitable 24vac transformer and a bridge rectifier!
Linear supply.
2 devices only?

#### PatrickMalarkey

Joined Oct 2, 2021
120
Very rare to find wound fields in DC motors for quite some time now.
All PM generally.
180 watt PM field magnets?

#### PatrickMalarkey

Joined Oct 2, 2021
120
....... A power supply consisting of a suitable 24vac transformer and a bridge rectifier!
Linear supply.
2 devices only?

#### PatrickMalarkey

Joined Oct 2, 2021
120

The motor, at start up, likely draws a lot more current than the 180W would suggest and so trips the supply protection system.
You could use a supply capable of a greater current. You could measure the resistance of the motor and so calculate the maximum current required by the motor (24V/motor resistance).
If you don't need the motor to start up quickly you could possibly use a NTC surge limiter to limit the initial current drawn by the motor.

#### shortbus

Joined Sep 30, 2009
9,808

#### crutschow

Joined Mar 14, 2008
31,585
Can you measure the actual current to the motor?