THREE-PHASE ASYNCHRONOUS
MOTORS WITH SLIP RING ROTOR
OUR SLIPRING MOTOR SUPPLY IS
DIVIDED INTO TWO SECTIONS
VEM MOTORS GmbH
AEM DESSAU GmbH
FRAME 132 - 315
FRAME 355 - 500
LOW VOLTAGE
LOW AND MEDIUM VOLTAGE
4-10 POLE
2-12 POLE
VARIOUS DUTY CYCLES
VARIOUS DUTY CYCLES
SLIPRING MOTOR EXPLAINED
o The slipring or wound rotor motor is an induction machine where
the rotor comprises a set of coils that are terminated in slip rings to
which external impedances can be connected
o The stator is the same as is used with a standard squirrel cage
motor
o By changing the impedance connected to the rotor circuit, the
speed/current and speed/torque curves can be altered
o Slipring motors are switched through their rotor circuit by inserting
suitable resistances and then removing them gradually
o Motor torque is directly proportional to external resistance
o Motor starting current is inversely proportional to the external
resistance
APPLICATIONS
o Because a slip ring motor is used primarily to
start a high inertia load or a load that requires a
very high starting torque across the full speed
range, slipring motors are best utilised (but not
limited to) the following applications:
o Overhead cranes and hoists
o Crushers
o Mill applications
o Mixers
ADVANTAGES OF A SLIPRING MOTOR
o High start-up torque
o Low starting current
o Minimal heat build-up on rotor (as heat is
dissipated via external resistors )
o Can be stopped & started more often than a
conventional induction motor
COMPARISON
SLIPRING MOTOR
INDUCTION MOTOR
The torque and power input may be varied in
The build of the rotor defines the torque curve
small increments during the start-up, as well as during start-up, which cannot be varied
within wide limits, by varying the resistor steps
inside the starter
By switching on a starter resistor in any phase
of the rotor winding, the start-up torque can
be changed. In fact the start-up torque can be
increased up to the breakdown torque by the
very choice of resistor. The start-up resistor is
reduced as the supply voltage is applied during
start-up and is eventually short-circuited.
When turned on directly, the motor will start
up according to its torque characteristic, the
start-up current being a multiple (normally
four to seven times) of the nominal current,
depending on the speed of the motor and
power output.
The size of the starter, the number of tapping
positions and the definition of the tap
resistors, orient themselves to the inertia of
the starting duty and to the starting frequency.
The fundamental mode of the motor voltage is
adjusted via phase control of varying degree,
and thus via torque and starting current.
During start-up the voltage drops down to a
value proportionate to the load. If the power
supply lacks the required capacity, another
starting method must be chosen.
VEM SLIPRING RANGE
• VEM manufacture slipring motors as per
customer specifications
• Duty cycles are S1 continuous rated to S4/S5
short rated (typically designed for crane
application)
• In the case of a replacement motor your
existing bearing, shaft and design arrangement
is fully accommodated by VEM
A typical schematic showing the
external resistors in circuit
PHYSICAL ADDRESS
POSTAL ADDRESS
28 BELL STREET
MEADOWDALE EXT.1
ROUTE 24
GERMISTON
P.O.BOX 15300
HURLYVALE
1611
SOUTH AFRICA
CONTACT INFORMATION
TEL:
FAX:
EMAIL:
Website:
011 974 8487
011 974 9704
sales@emac-online.com
www.emac-online.com
SALES CONTACTS
Mr. PETER MARTIN
Mr. CLINTON WADELEY
Mr. BRADLEY MEYER
082 653 6285
082 654 7700
082 327 7815
peter@emac-online.com
clinton@emac-online.com
info@emac-online.com