At the end of this module, you will be able to:
- State the purpose of adjustable speed drives
- Identify and describe the different types of adjustable speed drives
- Describe the importance of draw
- Identify and describe different section control modes
- Identify and describe safety hazards and guidelines associated with paper machine drives
The following key questions are answered in this module:
What is draw?
Draw is the speed difference between the sections of a paper machine and is usually expressed as a percentage.
How do DC drives work?
DC drives control the speed of the motor by varying the voltage. A DC motor's speed varies proportionally with the applied voltage.
How do AC drives work?
AC drives control the speed of the motor by changing the frequency supplied to the motor. The motor speed is directly proportional frequency.
What are common sectional controls?
Each section of the machine usually has run, stop, jog, crawl or slow, slack take-up, and draw controls.
What is a regenerative drive?
Under braking conditions, regenerative drives convert mechanical energy of the motor and connected load into electrical energy.
Below is a transcript of the video sample provided for this module:
The first type of sectional drives developed were adjustable voltage direct current drives. This type of drive operates on the principle that a DC motor's speed varies proportionally with the applied voltage. DC drives consist of a silicon controlled rectifier bridge which converts incoming AC volts to DC volts. During this conversion process, DC drives can regulate speed, torque, voltage, and current conditions of the DC motor.
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