Demonstration of a series wound DC motor (24 V, 746 W) and a
Curtis 1204-102 motor speed controller (24 - 36 V, max 175 A)

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Demonstration of a series wound DC motor (24 V, 746 W) and a
Curtis 1204-102 motor speed controller (24 - 36 V, max 175 A)

Report by Stefan Spännare, April 2011.

Note, print this web-page in landscape mode if it doesn't fit into portrait A4.


Contents

i. Warning
1. Introduction
2. Data for the electric motor and the Curtis controller
3. Some images (photos) of the setup
4. A short video of the motor running
5. References


i. Warning

The author makes no warranties that this document is free of errors.


1. Introduction

Interested in electric motors and steering systems I sometimes search for such things
on the advertisement forum Tradera in Sweden (see the references). March 12 2011 I
found and got this nice setup with a series wound DC motor (24 V, 746 W, 3450 rpm)
and a Curtis 1204-102 motor speed controller (24 - 36 V, max 175 A) for only 578
SEK (≈ $ 75) plus delivery costs. The seller didn't know if the things work, thereby
the low price. The motor is probably worth about 1000 SEK (≈ $ 125) and the Curtis
controller at least 1500 SEK (≈ $ 190) on the second hand market in Sweden. So this
was really a bargain. Perhaps I should also mention that this DC motor and the Curtis
controller originally comes from a Swedish transport moped ("flakmoped" in Swedish).

The wiring schematics is a bit complicated but I found help on Internet (see image
10 below) and by reading the manual for the Curtis controller. And it turned out that
these things work very fine. However one power cable connection to the motor was
burned due to overheating, but I managed to connect the cable via two 2.0 mm copper
wires directly to the brush holder on the motor. It works well (see image 4 below).

This Curtis controller does (unfortunately) not have regenerative breaking. But on the
other hand it can then be powered from a mains power supply (not only accumulators).


2. Data for the electric motor and the Curtis controller

Data for the electric motor and the Curtis controller is best seen from the info
signs on them in image 8 and 9 below. The motor sign is not so clear but
it is a series wound DC motor (24 V, 746 W and 3450) rpm as mentioned
earlier. Regarding the Curtis controller see also the brief info and the manual
in the references below.


3. Some images (photos) of the setup

1. Overview. The electric motor, the Curtis controller, the big relay and the large
power supply unit (2 - 24 V, max 15 A) with cables and Volt and Ampere meters.
This Curtis controller does not have regenerative breaking, so here it is powered
from the home built mains power supply (not accumulators).

2. A closer overview of the setup.

3. A closer view of the motor.

4. The overheated power cable connection on the motor was repaired by connecting the
cable via two 2.0 mm copper wires directly to the brush holder on the motor. It works fine.

5. The motor current when it is running idle at low speed.

6. The power supply voltage was adjusted to 24.00 V.

7. When I got the package the motor, Curtis controller and the big relay were
mounted on quite heavy steel holder with a cog belt gear.

8. The info sign on the motor.

9. The info sign on the Curtis controller.

10. A simplified wiring diagram found on Internet. The motor runs in only one
direction. A simple (two way) potentiometer is used as throttle for the motor,
which means that the upper throttle connection to the Curtis controller is not
connected. Otherwise my setup follows this diagram strictly.


4. A short video of the motor running

The motor is quite fast and powerful (24 V, 746 W and up to 3450 rpm).


5. References

Brief info and manual for the Curtis 1204-102 motor controller:

Some useful Internet links:


Author: Stefan Spännare
E-mail: stefan@NOspaennareSPAM.se (Please remove NO and SPAM before sending)
Latest update: 2011-05-14