ac & dc Motors & Generators 60-036

The Powerframes ac and dc Motors and Generators is a complete teaching package covering the key areas of electrical power and machines teaching. The machines are purpose-designed industrial machines of small physical size but with characteristics more typical of larger machines. The package is supplied with manuals, laboratory notes or software that provide a step-by step guide to setting-up and carrying-out the range of assignments associated with that package.

The Powerframes system is based around a series of bench-standing machines of nominally 250W rating. Power supplies, drive and control equipment, loading and instrumentation are all provided in the form of panels which mount into a purpose-designed, bench-standing frame and which can be easily slotted in and out as required. The frame is constructed of an advanced, fibre-loaded, rigid plastic material that is electrically insulating for safety.

Curriculum Coverage

The Separately Excited dc Motor

  • Principles of operation
  • Field current/shaft speed relationship
  • Armature voltage/shaft speed relationship
  • Armature current/output torque relationship
  • Effect of armature resistance on torque output

    Series Shunt and Compound dc Motors
  • Operating principles - Field current generation and shaft speed relationships
  • Torque/Speed characteristics of Series, Shunt and Compound motors
  • Comparison of characteristics
  • Armature current/torque relationships

    Separately Excited, Shunt and Compound dc Generators, Cumulative and Differential
  • Operating principles of a dc generator, residual magnetism, self excitation
  • Effect of field current variation on the generated output voltage
  • Generated voltage/shaft speed relationship
  • Critical resistance value in self excited generators
  • Output voltage/load current characteristics: Comparison of all types

    The Universal Motor
  • Field and Armature connections for ac and dc operation
  • Reversing the direction of shaft rotation
  • Torque/speed characteristics for ac and dc connections
  • Comparison of performance and understanding the need for compensation

    ac Induction Motors
  • Principles of operation of the Three Phase Induction motor
  • Identification of windings
  • Reversal of shaft direction
  • Determination of shaft speed
  • Torque/speed, current, power, powerfactor and efficiency and efficiency relationships
  • Effect on motor speed and torque with supply voltage changes

    Single Phase Induction Motors
  • Principles of operation
  • Starting requirements: Main and auxiliary windings phase relationships
  • Types of starting circuits: RL, LC and L only
  • Shaft speed, supply frequency, machine pole relationship
  • Torque/speed characteristic, current, powerfactor and efficiency
  • Effect on motor speed and torque with supply voltage changes

    Three Phase Synchronous Motor
  • Operating principles: Starting requirements
  • Synchronisation to the Three Phase supply
  • No load running conditions. Effect of variation in rotor current upon line current and powerfactor
  • Behaviour as a synchronous capacitor
  • Torque/speed characteristic, current, power, powerfactor and efficiency relationships
  • Effect of rotor current variations on motor pull out torque
  • Operation as a synchronous capacitor or inductor (Vee curves)

    Three Phase Synchronous Generator
  • Operating principles compared to the Synchronous Motor
  • Open circuit voltage characteristic
  • Effect of rotor current variation on output voltage
  • Effect of shaft speed variation on frequency and output voltage
  • Load characteristic and voltage regulation of a non synchronised generator, with capacitive, inductive and resistive loads
  • Short circuit test and determination of synchronous impedance
  • Synchronising procedure of the Synchronous Generator
  • Power generation: Effect on drive motor torque and output power with variation in field current
  • Behaviour of powerfactor with variation in rotor current

Equipment

ac/dc Power Supply

  • Circuit breaker protection
  • Comprehensive Power Supply
  • Three phase: nominally 0-200V ac line at 5A
  • 3 x Single Phase: each nominally 0-120V ac line to neutral at 5A dc nominally 0-140V at 6A
  • Three Phase 200V line, 120V Single Phase, fixed dc 110V 10A
  • Single Phase power distribution
  • Safety earth connection for all units

Universal Motor

  • Rated at 250W continuous
  • Maximum speed 6000 rev/min
  • Power requirements 110V dc or Single Phase
  • 120 ac 60Hz supply

dc Compound Machine

  • Rated at 250W with separately wound shunt and series fields
  • Nominal supply 100/110V dc armature and field
  • Suitable for operation with separately excited connections
  • Can be used as a dc generator
  • Nominal speed 3000 rev/min

Capacitor Start Motor

  • Rated 250W continuous
  • Rotates at up to 3600 rev/min at 60Hz
  • Power Requirements 120V Single Phase ac

Three Phase Synchronous Machine

  • Can be used as a motor or generator
  • Rated at 120/208V 300W
  • Synchronous speed 3600 rev/min at 60Hz
  • Power Requirement 200/208V Three Phase ac
  • Rotor supply 100V dc max

Three Phase Induction Motor

  • Rated at 250W
  • Rotates at up to 3600 rev/min at 60Hz
  • Power Requirement 200/208V star connected, 60Hz, Three Phase ac
  • Suitable for use with Star/Delta starters at reduced voltage

Switched Three Phase Resistance Load

  • Three resistor switched load banks
  • Seven resistor values per bank
  • 154 - 1080 ohms per bank
  • 100W per bank
  • Total Three Phase loading for Star @ 208V or Delta @ 120V, 300 Watts

Synchronising Lamps

  • Basic synchronising by Phase indicator lamps grouped in a triangle
  • Uses either lamps-bright or lamps-dark technique
  • A power switch is provided to connect the systems together.
  • Can accommodate Three Phase or Single Phase supplies.

Armature Current Dynamometer Machines Testing System
A complete automatic system for testing ac and dc electrical motors or generators, and Single Phase or Three Phase electrical systems.
Comprising:

  • dc shunt machine fitted with dc tachogenerator
  • Torque/speed control panel
  • Multi-channel I/O unit with I/O board & software

dc Shunt Machine fitted with Tachogenerator
The machine is mounted on a base unit with quick release catches and locating pins allowing easy coupling to other machines to be tested.
A multiway connector is provided for field and armature to connect to the torque/speed control panel. The dc tachogenerator attaches to the motor base and motor shaft to provide a dc voltage or current output for connection to the electronic systems or speed controllers.
  • Rated at 250W with separately wound shunt field
  • Normal supply 180/220V dc armature and field
  • Is used as a dc generator when operated to measure torque and can be used as a variable speed drive for the testing of generators and alternators
  • Operating speed range: 0-5000 rev/min-1 for torque and 0-4000 rev/min-1 when used as a variable speed drive
  • Tacho output: 2V dc/1000 to 6000 rev/min-1

Accessories

Patch Leads
For interconnections between panels and bench-mounted equipment, the leads are fitted with 4mm stackable shrouded safety connectors made from double insulated cable. All front panel power connections on the equipment are made with shrouded plug leads.
System Frame

  • Easy ‘lift-in/out' panel removal
  • Maximises bench space
  • Provides clear view of multi-panel experiments
    Universal Bin
  • Holds items associated with the Powerframes System
  • Can be used in either landscape or portrait format
    Shaft Coupling & Key
  • Couples 64 and 63 series machines and motors for motor/generator and multi-machine experiments
  • 14mm shaft to 14mm shaft