High Current Loads from DC motor

Hi guys

I would like to control a 4x4 winch motor (6hp DC motor) with an Arduino and possibly a motor driver.

A typical winch DC motor draws 400 Amps under high load, which is very high. I have found quite a few motor drivers online rated up to 100 Amps, however nothing for controlling this winch motor. I am going to be taking the winch off the 4x4 winch "setup" and using the winch motor alone without the large reduction gearbox.

I plan on using this winch motor because I have one and buying a new DC motor is very very expensive as Im sure you know.

Please could you offer some advice on controlling this motor?

I all probability a motor of that current rating used on a 4x4 for winching work will utilise series wound field windings. If that is the case it is unlikely to be suitable for speed control. I could therefore suggest you simply use the motor in on/off mode controlled via heavy duty contactor.

All DC motors can be speed controlled especially if they have field windings. But the controllers are specialized and thus expensive.

MarkT: All DC motors can be speed controlled especially if they have field windings. But the controllers are specialized and thus expensive.

I agree with your statement but [u]if[/u] the motor in question is a series wound motor (typical of a high torque low duration model), the windings generally carry the full load current. To effect speed control with sensible torque the field coils need full excitation with variable voltage to the armature. Building a 400A controller to feed the armature whilst developing around 2 volts or so for the field coils is way beyond the capability of a typical arduino user. However, if the OP wishes to purchase a controller such as may be supplied for ride-on electric locos or golf carts he will have to spend several hundred pounds/euros/dollars to do so and may well be dissappointed with results. Typical device shown here http://kellycontroller.com/kdz2440012v-24v400aseriespm-p-943.html

But you can PWM the field coils to give torque control and wrap a speed control loop round that.

[ Actually that's not going to work, you need to limit armature current anyway, so you are right a 400A controller is needed - but control of the field coil is normally thrown in with that, allows field-weakening. ]

I guess having to power a 6hp motor from 12V is very compromized...

Field weakening (reducing volts/current) gives an increase in speed Armature weakening (reducing volts/amps) gives a decrease in speed

So any controller designed to control speed of a DC motor with series wound coils has to increase one whilst decreasing the other. Therefore the motor internals would have to be reworked to permit suitable independant access to both field and armature for control

Here's a good book on the subject: "Electric Motors and Drives" ISBN-10: 0-7506-4718-3

There appears to be an online version.

and another here http://www.electrical4u.com/series-wound-dc-motor-or-dc-series-motor/

Although field weakening gives increase in speed there is a major loss of torque which kind of defeats the purpose.

The OP should also be aware that running a series motor "off-loaded" may permit its speed to increase to destruction

Playing with field wound series motors is a serious business :)

Playing with any high power motor is a serious business.

Hi guys,

Thanx for the input! My problem is that DC motors are expensive, but I have a serious 4x4 winch motor on my 4x4. Therefore I wanted to investigate if I could use this winch for the drive on a high speed winch. I want to make a "wake winch" and would like to make it electric.

There are many factors to consider when making a wake winch, but due to my budget I would like to use this winch motor and check how it can be controlled. I love the idea of using an Arduino and motor driver, but this motor draws high current.

So basically it is not possible? What other options are there? In having this motor nd not needing to buy a new one I can afford a motor driver and other parts?

Please carry on advising!

Here is the link for the motor specs:

http://www.t-maxwinches.com.au/documents/TMAEW9000wire.pdf

I want to use only the motor because the reduction gearbox will be too slow for a high speed winch.

I really hope there is a way to make use of this motor for my wake winch - https://www.youtube.com/watch?v=JPA0ZcPgXvM

6HP will pull your arms out!! I doubt you need anything like that much power to aquaplane...

MarkT: 6HP will pull your arms out!!

Based on what was done for punishment during medieval times I would guess one horsepower is sufficient for such things.

and that's both arms plus legs :)

I once saw a similar system over 50 years ago used for greyhound training, but that involved a jacked up car with one wheel rim acting as the capstan drum.

The spec sheet for this winch is 9000 lb max pull with a 178:1 gear ratio so removing the gear ratio would only give about 50 lb cable pull--this would give lots of acceleration but (I hope) is within human capability. According to the spec sheet it is a series motor so it cannot be reversed by reversing the terminal voltage. From the picture it looks like some sort of reversing lever going into the gearbox so if you bypass the gearbox you have to think about how you will reverse. I think likely that 9000lb rated pull is at standstill so the 50 lb would also be at standstill and would drop off rapidly as speed increased. There are a lot of "might works" here so you almost have to try it to see what happens;-- and you might not even need a speed controller!!