Page 204 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

1 Main drive assembly
2 Terminal cover
3 Terminal cover retaining screw
4 Blank cover

5 Keypad
6 COMMS technology box (optional)
7 Speed feedback technology card ( optional)
8 Gland plate

9 Power terminal shield
10 Power terminals
11 Control terminals
12 Earthing / grounding points

13 Keypad part
14 Programming part
15 Auxiliary power, external contactor, blower and isolated thermistor terminals
Power and control terminals

In DC drive, the front panel has the power terminals L1, L2 and L3 where 3 phase input supply of 415V can be
connected.
There are control terminals given for speed adjust potentiometer, Torque adjust potentiometer, START/RUN/
STOP switch, JOG/RUN/ switch, AUTO/MAN switch, FORWARD/REVERSE switch etc. Terminal A1 & A2 and
B0 & B1 are meant for armature and field connections respectively. Names and locations are illustrated in Fig 5.
Advantages of DC drive

• DC drives are less complex with a single power conversion from AC to DC.
• DC drives are normally less expensive for most horsepower ratings.
• DC motors have a long tradition of use as adjustable speed machines and a wide range of options have
evolved for this purpose.
• Cooling blowers and inlet air flanges provide cooling air for a wide speed range at constant torque.
• Accessory mounting flanges and kits for mounting feedback tachometers and encoders.

• DC regenerative drives are available for applications requiring continuous regeneration for overhauling loads.
AC drives with this capability would be more complex and expensive.
• Properly applied brush and commutator maintenance is minimum.

• DC motors are capable of providing starting and accelerating torques in excess of 400% of rated value.
• Some AC drives may produce audible motor noise which is undesirable in some applications.
Disadvantages of DC drive
• More complicated because of commutators and brushes.
• Heavier than AC motors.

• High maintenance is required.
• Large and more expensive than AC drive.
• Not suitable for high speed operation.

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CITS : Power - Electrician & Wireman - Lesson 93-100 CITS : Power - Electrician & Wireman - Lesson 93-100