DC Motor in Series or Parallel

One thing that should be considered is how the motors are linked mechanically.

Are the motors all turning at the same speed? Do they all see the same load (torque)?

If the DC motors are wired in parallel, of course, all will have the same voltage. When a DC motor runs, it acts as a generator, generating a reverse EMF proportional to the speed. The amount of current drawn by the motor is equal to the applied voltage (24v) minus the reverse EMF, that divided by the motor resistance. So if a motor is running slower than the others, it will draw more current.

The torque supplied by the motor will be proportional to current. Conversely, the amount of current drawn by the motor will be proportional to the torque needed, which is determined by the load. (Torque supplied by motor equals torque needed by load).

The following may help in sizing circuit breaker size:

https://www.electricaltechnology.org/2020/02/calculate-circuit-breaker-size.html

Thank so much mate.

They have same load , and same load.

Follow instruction from manufacture, they advise me to run 3 motor in 30m distance ( total) + 4mm2 cable.

I could not do that.

in your opinion can i run 6x motors in 35m ( total distant ) by using 4mm2 cable ( extra low voltage cable) . Distance from first motor to power supply is 1m.

I'm worries about voltage drop as well, max acceptable voltage drop for motor is 3V.

Thanks

Each 24 volt motor will only receive 3.43 volts if you wire them in series.

Yes mate, I brought power supply already so parallel is only option for me now.

Thank mate

https://www.elkoba.com/pdf/artikel/rsp-1500-spec.pdf

Thank mate. I'm using this one . But don't have much idea for using remote sense compensate voltage drop as i use one power supply to feed 4-6 motors.

Do you have any idea on installing DC motor ? Distance about 40m in total.

Also what cable do you using ? Extra low voltage or same as 240V ?

Thanks

wire calculator for 24 volts...You always want to oversize your wire a bit....and have an insulation coating appropriate for the operating environment...

150 watts at 24 volts = 6.25 amps #12 awg is good for 121 feet at 70°F....

https://www.securitypower.com/Other/securitypowerCOM/04%20-%20Application%20Notes%20-%20Tools/AN-2-24_Wire_Table.pdf

https://www.multicable.com/resources/reference-data/cross-reference-awg-to-mm2/

If you don't mind, why is the power supply being mounted so far from the motors?

If you could sketch a layout with rough est of dimensions, that might be a good idea....It would be a lot cheaper it seems to run 1 small wire to the power supply and several short wires to the motors...

Supply the motors from the center (distance wise) of the set of motors.

This will reduce the voltage drop considerably by cutting your distance in half.

If this is not possible,go up one size in the feeder wiring.

There is no point in wiring these in series.

The choice of <...circuit breaker...> is determined solely by the wiring used, on which topic the post is silent. If in doubt, consult a local Electrical Engineer.

In the UK, cable sizing and circuit protection is determined by the protocol found in British Standard 7671. Other jurisdictions have their own local applicable standards.

There are dozens of earlier threads within CR4 on this topic and it would run contrary to Site Rule No.6 to duplicate them in this thread.

Thank so much guys!

My customer copy design from his neighbor.

His neighbor has 150m( long)x 60 ( wide) greenhouse. An electrician has installed 21 motors -24V 100W - 6.2A DC , divided by 3 set ( 7 motors per set). Each set has powered by 1x24V-1000W- 40A meanwell power supply.

Power supply has been installed in 1 corner of the greenhouse. Max distance is 150m away from power supply.

Still working for 2 years. <----- I'm so curious. I asked him to have a look but they declined . Also they are doing same thing for new greenhouse ( same dimension , same motor + power supply...)

------

Back to my job:

- Today i spent an hour to explain to my customer about his neighbor electrical design and i did not want to follow, then i did move DC power supply to middle of them. Cut from 150m to only 44m. Control panel is still near entrance. My set of 6 motors worked well, not generated heat.

I could not follow manufacture's instruction , they are very tough . It is recommenced to run a set of 5 motors( same motor as mine) -150m long - 25A need to use 25mm2 cable .

Thank all of you for helping me. If you have same project ( Electrical for Greenhouse ) can you share your experience?

My next project is remote control those motor ( PLC- HMI) , installing rain sensor + thermal meter so they can close when raining and open when over 30 degree ( 86F).

Also pumping system from Holland has all feature ( remote control...) , anyone know

where can i learn to connect to ?

Thanks

Kevin

Were the equipment for a <...greenhouse...> to be <...remote control...PLC- HMI...> then it may prove possible to sequence the <...motor[s]...> so that only 1 is on at any time, leading to reductions in power cable sizing and circuit breaker selection.

However, adding these details in at this stage might be considered "mission creep" in some quarters and in the context of the original post, therefore:

<unsubscribes>

The voltage drop, under full load, to the last motor will be approximately .63 volts.

This is based on a a resistance of 4.3 ohms per 1000 ft of your wire size.

You have cut your distance in half,so this will be reduced accordingly.

Check your motor specs to see if this is acceptable.

DC motors are usually very tolerant of voltage variations.

The problem you may encounter,is a slight reduction in speed/torque of the farthest motor.

This might result in one end of the film moving slightly slower than the other,if there is a motor at each end.

I would increase wiring size one step up,just to reduce voltage drop if this is a problem.

Most modern power supplies are internally overload protected,so the feeder wire to the power supply is your main concern.

Some power supplies allow compensation by removing a jumper on the board and applying a sensing wire from the end of the circuit.I don't think you will need this in your application.

Size the fuse according to the input rating of the supply,not to exceed the rating of the conductors feeding it.

All conductors must be rated for the HIGHEST temperature encountered by the conductor at ANY point on the conductor.

Be aware,in the States,an unlicensed electrician does not have to be paid by the customer,and there are penalties for the violator as well.

This may apply or not in your case.

"Be aware,in the States,an unlicensed electrician does not have to be paid by the customer,and there are penalties for the violator as well."..

Could you cite the law that says this...? Have you refused to pay people you hired to do work?

I am a retired unlimited electrical contractor,and the 7 southeastern states where my license is reciprocal this is generally the law.

The unlicensed person performing the work is subject to a fine and a court order to cease and desist.

Any further work is considered contempt of court and they will be enforced charges.

If the worker takes the issue to court,the judges decision is final,but chances of winning are slim.

I know of an instance where a worker completely wired a sawmill and the owner refused to pay because he was not licensed.

He lost in court,plus had to pay the owners legal fees,and incurred penalties from the Electrical Board.

Ironically,the sawmill burned to the ground a year later.

Rules may vary from state to state.

It pays to check local codes and laws,as always.

https://www.gro-techsystems.com/

A <...circuit breaker...> doesn't <...prevent short circuit...>. It is there to protect the wiring.

Thank so much guys for your help.

I took over existing works and did not have detail of motor long enough for planning.

Detail from factory is quite simple , they are focus on mechanical instruction rather than electrical instruction.

After field testing , i can say 4 set of motor is the best choice, Power supply should install in middle . 25A distance is 10M ( from power supply to furthest motor) , Cable can be 14AGW ( 2.5mm2).

220-110V Motor version is available, and cheaper. Will try some for next project.

Remote control is not suit for this topic so i will post in different topic .

Will spend time to learn Gro-Tech + DC voltage drop this weekend as I'm newbie in Framing + Green house.

Appreciated!

Kevin