Motor and Drive Principles

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Chapter 1

• Motor and Drive Principles

Electric Motors Motor Torque Electric Motor
Drives
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• The motor power rating is located on the motors
  nameplate, which is affixed to the motor, and
  also includes information such as voltage and RPM
  ratings.

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• A portable oscilloscope can be used to measure
  true power, apparent power, reactive power, or
  power factor.

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• The applied voltage to a motor should be within
  10 to 5 of its voltage rating for best
  performance.

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• The nameplate rated current of a motor is the
  amount of current the motor will draw when fully
  loaded.

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• When voltage and current decrease together, the
  problem is in the power source and distribution
  system.

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• As current in the circuit increases, voltage
  decreases at a lesser rate.

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• Because most motor manufacturers balance their
  motors at speeds 25 over nameplate rated speed,
  it is recommended to not operate a motor at 20
  or more than its nameplate rated speed.

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• Although motor drives can be set and programmed
  using switches and potentiometers, most motor
  drives use a keypad to program motor operating
  parameters.

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• Start boost applies higher voltage initially and
  then follows the constant torque V/Hz pattern.
  Continuous boost applies higher voltage from zero
  to base speed.

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• The amount of boost a motor requires is dependent
  upon the type of load the motor operates.

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• Maximum operating temperatures for motor
  insulation are classified by the National
  Electrical Manufac-turers Association (NEMA) and
  the International Electrotechnical Commission
  (IEC).

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• The four types of torque produced by a motor are
  locked rotor torque (LRT), pull-up torque (PUT),
  breakdown torque (BDT), and full-load torque
  (FLT).

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• A motor may be fully loaded, underloaded, or
  overloaded.

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• Motor loads may require constant torque (CT),
  variable torque (VT), or constant horsepower (CH)
  when operating at different speeds.

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• If verification, documentation, or analysis is
  required, a portable oscilloscope can be used to
  capture and display measurements taken under
  different settings and circuit operating
  conditions.

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• Basic programming parameters consist of the most
  commonly used programming parameters.

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• Display parameters are used to give a visual
  display of operating conditions.

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• The three main sections of an AC drive are the
  converter, DC bus, and inverter sections.

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• Pulse width modulation is used to produce a
  pulsating DC output.

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• When testing or troubleshooting an installed
  drive, a portable oscilloscope can be used to
  closely analyze the drives PWM output.

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• As conductor length increases and an electric
  motor drives output carrier frequency increases,
  the transient voltages become larger.