Does the control unit power must equal to motor power

Thread Starter

Kelvin Lee

Joined Oct 22, 2018
110
Dear Sir/Madam,

My question may be a bit foolish, hope someone can help.

I have a battery 24V 12AH, a control unit 24V 500W and a motor 24V 250W, may I know whether any problem if I connect them all together where the power of the control unit is 500W and the motor is 250W.

Best regards,

Kelvin
 

LesJones

Joined Jan 8, 2017
2,497
As Eric says it should work. One thing to consider is that some designs of speed controller have over current protection. If the one you have has this function it will not protect a 250 watt motor as the current limit value will be designed for a 500 watt motor. You would need to look at the schematic to see if this is the case.

Les.
 

Thread Starter

Kelvin Lee

Joined Oct 22, 2018
110
As Eric says it should work. One thing to consider is that some designs of speed controller have over current protection. If the one you have has this function it will not protect a 250 watt motor as the current limit value will be designed for a 500 watt motor. You would need to look at the schematic to see if this is the case.

Les.
Thanks, Les, what do you mean if the controller has over current protection and it will not protect the 250-watt motor? Should the controller has over current protection is a good design or not?
 

MaxHeadRoom

Joined Jul 18, 2013
20,000
You also need to consider motor load and whether the motor is under load at start.
An example application of this is a typical treadmill belt motor which often is called to start with high load connected, circuitry is in place so that any start command causes the control to go through gradual acceleration to the set point.
Max.
 

Thread Starter

Kelvin Lee

Joined Oct 22, 2018
110
You also need to consider motor load and whether the motor is under load at start.
An example application of this is a typical treadmill belt motor which often is called to start with high load connected, circuitry is in place so that any start command causes the control to go through gradual acceleration to the set point.
Max.
Thanks for your advice, Max.
 
Motor selection for a particular VFD could be a little more complicated. See https://www.vfds.com/blog/vfd-buying-guide

As they become further and further apart, eg 10,000W for a 200 W load, the minimum current limit would be in a bad range.

Sizing generators for motors, you have to look at VA, not Watts because of the start-up current. TH VFD can lessen the start-up current significantly.

@MaxHeadRoom Why don't they use VA? EDIT: "use" WAS 'us".

A 500 W controller for a 250 W motor sounds good. Post the specs.
 
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