Medium voltage switchgear application guide

Medium voltage switchgear application guide
Appendix 2: motor
(cont’d)
4 - DIFFERENT MEDIUM VOLTAGE MOTORS
Alternating and 100 kW current to 40 MW medium ranges. voltage motors are situated in the2 kV to 14 kV
The applications motors can are be given classed in the in table 4 families below. whose main characteristics and
motor characteristics, advantages applications
type
drawbacks
asynchronous ■ highly robust due to their ■ intensive use
motors with simple construction ■ aggressive or
single cage, ■ hardly any on-load speed dangerous atmosphere
double cage,
or deep slots
variation
■ high quantity of reactive power
absorbed with weak load
asynchronous ■ easy optimisation of starting ■ machines with high starting
motors with torque or signal torque
widing rotor ■ rotor resistances and rings needing ■ machine needing strong
adjustment and maintenance
counter-current breaking
■ power factor usually
■ tending to give way to
lower than 0.9
double cage motors
synchronous ■ same technology as ■ P > to 2000 kW
motors
alternators
■ high transient state
■ good output and good power
factor
synchronised ■ mixture of two previous ones: ■ tending to disappear
asynchronous good starting torque and good
motors
power factor
■ complex starting co-ordination
5 - DIFFERENT MV ASYNCHRONOUS MOTOR STARTING TYPES
J L
J C J L
J C
J N
J L J L
J R3
M
R 3
J R2
R 2
J R1
M
M
M
R 1
date
11/94
- B•3•2 -
revised
05/2004
direct auto-transformer reactance rotors
6 - ASYNCHRONOUS MOTOR CHARACTERISTICS
Direct characteristics
asynchronous starting
voltage
are motors
power
The the most widely used.
starting current
influencing main characteristics motor operation no-load current
are opposite. given in the table
asynchronous motor
2 kV to 14 kV
100 kW to 40 MW
6 to 7 times motor I n
≈ 0.3 times motor I n
starting current cos ϕ 0.1 to 0.2
no-load current cos ϕ ≈ 0.1
load current cos ϕ 0.7 to 0.9
page 5