This is a 'legacy' document, written in the mid 199s. However the Atco motor is not recommended and you use these motors entirely at your own risk. Not only is it a difficult motor to wire and control, but old, used motors are likely to be in bad condition and this causes arcing at the commutator which can destroy controllers. See MOSFET failures
The information which follows is given in good faith and without any acceptance of liability and it should not be taken as encouragement to use these old motors.
There are a number of Atco electric lawnmowers being scrapped. This application note describes how to use their motor. Of course, there may be more recent models - to which these notes may not apply.
These are shunt wound motors (i.e. a separate, wound field which is connected in parallel with the armature). They are an old design and are therefore quite large for their power output. However they can be used with our controllers. For best motor efficiency and slow motor speed control you should separate the field from the armature, connect the field winding permanently across the battery and run the armature from our controller. If you do not separate the field you won't damage our controller but you won't get good slow motor speed control and the motor will be very inefficient at low speeds.
The negative end of the field winding is connected to the chassis by the bolt which also is the battery negative connection. It is easy to disconnect it and bring it out separately through one of the holes in the motor end plate. If you wish to reverse the motor you need also isolate the positive end of the field winding in the same way.
Another snag is that the motor's case is permanently connected to one of the armature connections. Provided the battery and all electrics are 'floating' (i.e. there is no connection to the frame) this is not a problem. Otherwise you must use insulating mountings (and shaft) to isolate the motor from the chassis. Alternatively you could connect the motor's case to the battery positive (which is the 'common' terminal on our controllers) and work with a positive chassis. This is only practical if both ends of the field winding are isolated.
The diagram shows the wiring of a converted mower.
To reverse the motor, simply use a double pole changeover switch (DPCO) to reverse the field connection as shown.
The motor is rated at 25 amps continuous. Intermittently it should take up to 3 or 4 times this current, so it would seem ideally suited to a 2QD-70 controller, depending on the mechanical loading.
You can also use an NCC controller to operate the armature: if you have an NCC-70 the parking brake driver could be used to energise the field winding.