There are various types of motor speed controllers manufactured by Curtis Instruments. Each one of them is designed in order to serve a specific function according to demand and application. When viewing Curtis controllers, different identifiers are included in the label or product specification that indicates functionalities setting each controller apart from one another. Some of these are unfamiliar technical terms such as ITS, PDS, SepEx, DC Series Wound Motor, and PMC. In order to better understand these terms, here’s an overview of each one of them.

The terms discussed in this article:

• ITS

• PDS

• SepEx

• DC Series Wound Motor

• PMC

1. Curtis (ITS) Controller

Curtis ITS Controllers have Inductive Throttle Sensor for throttle input. There are various throttle types that work for Curtis controllers. However, only a few specific models are designed to work with an ITS throttle. An ITS throttle is also a two-wire electronic throttle that connects two pins.

Wiring Diagram for Curtis Controllers with ITS Throttle

For example, In Curtis 1268, an ITS throttle connects Pot High Pin and Pot Wiper Pin. Within the throttle, there is circuitry for a Hall sensor responsible for creating an output current. This current ranges from 0.7 mA to 1.6 mA, which also indicates the minimum and maximum current of the throttle. The wires can be interchanged. The diagram below is the ITS Throttle wiring for Curtis 1268.

Note: It is important to know that the number assigned for pins varies from model to model. For example, in Curtis 1266, the ITS throttle connects the same pins but with different Pin numbers. The Pot High Pin and Pot Wiper Pin for Curtis 1266 are Pins 4 and 5, respectively.

Characteristics of Inductive Throttle Sensors

• Highly reliable due to it being contactless

• Compact design compared to similar sensors but requires PCB

• Allows either analog or digital interface

• Easy to calibrate

• The temperature drift is low

• The accuracy is high compared to similar sensors

• Good sensor resolution

• Equipped with safety features in case of a detected error

• Complies with ISO standards whereas similar sensors don’t

• Meets specific industry standards and qualifications for automotive applications

Sample Models

Some Specific Products with ITS Throttle:

• Some 1268 Models

• 1268-5502 : Curtis Controller G - 36-48V 500A (ITS) SX CTL #1268-5502

• Some 1204S Models

• Curtis 36/48V 450A (ITS) PMC 1204S-5404

• Some 1205 Models

• Curtis 24/36V 400A (ITS) PMC 1205-117

• Curtis 36/48V 350A (ITS) PMC 1205-210

• Curtis 36/48V 370A (ITS) PMC 1205-211

• Some 1205M Models

• 1205M-5606 : Curtis Controller G - 36/48V 500A (ITS) PROG PMC #1205M-5606

• Curtis 36/48V 500A ITS 1205M-5606

• Curtis 36/48V 500A ITS 1205M-5607

• Some 1206HB Models

• Curtis EZGO 48V 250A (ITS) Controller 1206HB5201

Additional Information About ITS

1. ITS is an abbreviation for Inductive Throttle Sensor

2. ITS is a throttle type

3. Inductive Sensing is a technology used in Curtis controllers as it is a straightforward sensor that can also be integrated with an existing control system

4. ITS is a hall effect sensor

1. EZGO ITS is utilized in determining the positioning of the throttle. The throttle placement is then sent as data to interpret the amount of energy the motor needs to release

2. A hall effect sensor: an electronic device detecting the hall effect and translating it to electronic data that can perform functions such as turning the circuit on and off, measuring changing magnetic fields, and the data can be processed/stored/displayed.

• These sensors are non-contacting position sensors causing them to last longer and be regarded as wear-free sensors. They can also be and can be either linear or rotary.
  
  

2. Curtis PDS Controller

A PDS is an identifier of the Drive System that the vehicles used. The PDS is known as the precision drive system and it has only been utilized exclusively for EZGO carts since 2000. It has a separate motor that is capable of having a regenerative braking feature and the parameters are programmable, which aids in maintaining the engine. A PDS setting should only be adjusted due to demand. As an example, the driver may increase acceleration speed when going uphill. However, the setting for that terrain is unnecessary when driving on flat surfaces and it may drain your power supply faster.

A precision drive system (PDS) specifies the 36 volts 2nd generation system of Shunt Wound Motor utilized starting 2000 until 2010. It is commonly used for 1206 controller models like the drive control systems (DCS). The PDS utilizes a rocker switch rather than a lever switch, there are multiple connectors on a PDS, and there is a speed sensor on the motor.

The PDS controller models have a feature that stops moving vehicles that are unattended. A PDS car has a governor feature that regardless of the ground surface, it can hold constant ground speed at full pedal. Under the seat of a PDS car, it also has a toggle switch that is marked “Tow/Maintenance” and “Run”

Ways to determine whether a golf cart has a PDS:

1. Open the motor and look for an environmental black plastic cover. Usually, it is PDS if there are a number of diagnostic codes listed on its outer part.

2. PDS has a rocker switch on the dash or between the legs under your switch and a run/tow switch.

Sample Models

• 1206MX Models

• Curtis EZGO 36V 300A PDS Controller 1206-MX

• Curtis EZGO 36V 350A PDS Controller 1206MX4301

• 76-1206-MX : Curtis 1206-MX EZGO PDS 400A Upgrade

Additional Information About PDS

1. PDS is an abbreviation for Precision Drive System

2. Formulas involved with Shunt Wound Motor:

1. Current:

1. Armature Current

IArmature = ISupply - IShunt

2. Shunt Field Current

IShunt = VSupply ÷ RShunt

2. Voltage Supply

VSupply = Back EMF + IArmatureRArmature

3. Curtis SepEx Controller

The Curtis SepEx Controllers are designed to control Separately Excited Motors.

SepEx Controllers, in general, provide a more dynamic motor control as it controls both the motor field coil current and the armature voltage. This dynamic control is seen as regenerative braking and speed control. As of early 2023, the available Curtis SepEx motor controllers are applicable for traction purposes. The models available are Curtis 1266 and 1268. There are older SepEx controller models such as Curtis 1243, 1244, and 1264

About the Motor:

The main field winding of a separately excited motor is excited by an external constant-voltage power source. It is separately excited where two power supplies are necessary. One power source for the armature and the other one is for the field winding. This motor is mostly applicable for vehicular traction applications.

Sample Models

There are 2 models of SepEx controllers available on the Curtis website. These models are Curtis 1266 and 1268. There are also older models such as Curtis 1243, 1243G2, and 1244. They are mostly used for traction applications.

• 1266 Models

Nominal Voltage: 36 V, 48 V

Maximum Current: 350 A

• 1268 Models

Nominal Voltage: 36 V, 48 V

Maximum Current: 500 A

• 1243 Models

Nominal Voltage: 24 V, 36 V

Maximum Current: 350 A

• 1244 Models

Nominal Voltage: 24 V, 36 V, 48 V, 80 V

Maximum Current: 700 A

Additional Information About SepEx

3. SepEx stands for Separately Excited

4. Separately Excited DC Generator - has an independent external source supplying the field winding. The speed of armature rotation and field current dictates the amount of generated voltage. Therefore, higher voltage is generated with greater speed and field current.

5. Formulas involved in Separately Excited Motors

1. Armature Current

IArmature = ISupply

2. Voltage Supply

VSupply = Back EMF + IArmatureRArmature

3. Electric Power in the Armature

E = Back EMF x IArmature

4. Curtis DC Series Wound Motors Controller

The Curtis DC Series Wound Motor Controllers can be applied to either traction or pump applications. For traction application, the latest Curtis controllers are the Curtis 1204M, 1205M, 1209M, and 1221M models, which are also replacements for older non-programmable models (1204, 1205, 1209B, and 1221B). Meanwhile, for pump application, the latest controllers are Curtis 1216 and 1253 models.

About the Motor:

Series Wound DC Motor has field windings and stator windings in a series connection. Due to this, the current of the armature is equal to the field current. The current flow is thicker since it is directly from the power supply causing an increase in the load-carrying capacity of the motor. This provides a high magnetic field that consequently produces very high torque.

• High Torque in a motor indicates a shorter delay for the motor to respond from a given input such as pressing the gas pedal.

• Increase in current = increase in torque

Three ways to control the motor speed of a DC motor:

1. Flux Control Method - a rheostat and field winding is in series connection

• Rheostat increases the series resistance to reduce flux and increase the speed of the motor

2. Voltage Regulation Method - a method used in Shunt DC motors. Two ways to do this:

1. Multi-voltage control: Connect an exciting voltage to the shunt field while supplying different voltages to the armature

2. Ward Leonard Method: Supply varying voltage to the armature

3. Armature Resistance Control Method - follows the principle that states the motor speed is directly proportional to the back EMF. Therefore, maintaining armature resistance and supplied voltage, the motor speed will be in proportion with the armature current.

Sample Models and Specs

• As of Early 2023, the Curtis controllers that are designed for DC Series Wound Motors are applied on Traction and Pump Motors, and these are the following models:

• Traction

• 1204M Models

Nominal Voltage: 24 V, 36 V, 48 V, 60 V, 72 V

Maximum Current: 500 A

• 1205M Models

Nominal Voltage: 24 V, 36 V, 48 V, 60 V, 72 V

Maximum Current: 500 A

• Models 1207, 1207A, 1207B

Nominal Voltage: 24 V, 36 V

Maximum Current: 300 A

• 1209M

Nominal Voltage: 36 V, 48 V, 60 V, 72 V

Maximum Current: 450 A

• 1221M

Nominal Voltage: 48 V, 60 V, 72 V

Maximum Current: 550 A

• Pump

• 1216

Nominal Voltage: 24 V

Maximum Current: 360 A

• 1253

Nominal Voltage: 48 V, 80 V

Maximum Current: 600 A

Additional Information About Series-Wound DC

1. A DC Series Wound Motor is a DC motor with its field winding in a series connection with the armature winding. The field winding in a series connection is carrying the whole armature current causing the thick wires to have few turns, possessing low resistance, and the motor draws a significant amount of current.
   

Since it is in series, the Current of the series coil (ISe) is equal to the Current of the Armature (IA) and the Supply Voltage is equal to the sum of the Back EMF and the Current is multiplied by the sum of Resistance in armature and Resistance in the series coil. Or simply

Supply Voltage = Eb + IA (RSE + RA )

2. One notable advantage of a Series-Wound Motor is that it can produce high torque and allows low-speed operation. This motor configuration is often applied to traction, pump, and other heavy applications as these heavy equipment are moved at a relatively slower pace while lighter loads move in a faster manner.

5. Curtis PMC Controller

Curtis PMC is the former name of the California Research and Development Center. The Curtis PMC controllers are designed by Curtis PMC and protected by U.S. Patent Number 4,626,750. It is a solid-state D.C. motor control invented by Stephen F. Post.

Characteristics of Curtis PMC

• Curtis PMC motor controllers have operator control that is highly superior in terms of the drive speed of a motor.

• These controllers are designed to be used in various applications and can be installed in a lot of ways according to demand.

• The controllers from Curtis PMC 1200 series have PWM with a high frequency of 15 kHz, making it an efficient and noiseless, and stepless controller option.

• The PMC controllers should also barely get warm due to the efficient thermal design

• Contains sensitive components for electrostatic discharge (ESD) to protect them from damage. (1268 Models)

Sample Models

• As of Early 2023, the only Curtis PMC controller available on their website:

• 1268 Models

Nominal Voltage: 36 V, 48 V

Maximum Current: 500 A

• Old Models from Curtis PMC 1200 series

• Models 1203A, and 1203C

Nominal Voltage: 12 V, 24 V, 36 V

Maximum Current: 90 A

• Models 1204, 1204M, 1204S, and 1204X

Nominal Voltage: 12 V, 24 V, 36 V, 48 V. 72 V

Maximum Current: 400 A

• Models 1205, 1205M, 1205S, and 1205X

Nominal Voltage: 12 V, 24 V, 36 V, 48 V. 72 V

Maximum Current: 500 A

• Models 1207, 1207A, 1207B
  Nominal Voltage: 24 V, 36 V
  Maximum Current: 300 A

• Models 1208, 1208A, 1208C

Nominal Voltage: 12 V, 24 V, 36 V

Maximum Current: 70 A

• Models 1209 and 1209B
  Nominal Voltage: 12 V, 24 V, 36 V, 48 V. 72 V, 80 V, 120 V
  Maximum Current: 500 A

• 1210 Models

Nominal Voltage: 24 V

Maximum Current: 70 A

• Models 1212 and 1212P

Nominal Voltage: 24 V

Maximum Current: 90 A

• 1213 Models

Nominal Voltage: 24 V, 36 V, 48 V

Maximum Current: 200 A

• 1214-8 Models

Nominal Voltage: 24 V, 36 V, 48 V

Maximum Current: 400 A

• 1215-8 Models

Nominal Voltage: 24 V, 36 V, 48 V

Maximum Current: 500 A

• 1219-8 Models

Nominal Voltage: 24 V, 36 V, 48 V

Maximum Current: 600 A