Download Vector - Morrell

MAC DIVISION
Asynchronous vector motors
INVERTER DRIVE: WHICH MOTOR TO USE WITH?
 Are you planning to run a
marathon in high-heeled
shoes?
 Then, why are you using an
standard asynchronous
motor in your variable speed
application?
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STANDARD MOTOR vs VECTOR MOTOR
Design priorities:
PARAMETER
STANDARD MOTOR
VECTOR MOTOR
O peration
Directly from the mains
Inverter duty
V/ F ratio
Fixed (4 0 0 V/ 5 0 Hz in Europe)
Variable, depending on the application
The inverter allows different V/ F ratios
Power factor
Parameter to be maximised
It reduces the reactive power consumption
It' s not a priority
The inverter corrects the reactive power consumption
Starting peak current
Parameter to be minimised
It will determine the protections
There' s no starting peak values due Inverter duty
Starting torque
To be maximised
Nominal Torque from 0 rpm' s
Inertia
Not important
It' s not designed to be used in variable speed
To be minimised in order to have the best dynamic
performances
Peak Torque
-
To be maximised
To match the Inverter current limits
Cooling system
Self cooling system
Active Fan cooled
The best performances from 0 rpm' s
Constant Power Range
Not important
It' s not designed to be used in variable speed
To be maximised
Wide working zone in field weakening mode
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CONSTRUCTIVE DETAILS
Active Fan
cooling system
Reinforced materials and
vacuum impregnation
Low losses
laminated square
frame
Integrated
encoder
connector
Second shaft for
encoder fitting
Integrated PTC for
thermal winding
protection
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Parking brake
option
Low inertia Rotor
MOTOR PERFORMANCES: STANDARD vs VECTOR
200 %
160 %
100 %
Nm
40
50
70
125
Hz
Nominal
Overload
Standard
Vector MAC Q
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.
Nominal
Overload
TYPICAL PROBLEMS USING STANDARD MOTORS FOR INVERTER DUTY
 Motor warming at low speed operation

Standard: Insufficient motor cooling working at low speeds due a self cooling design.

Vector: Perfect motor cooling at any speeds thanks to its active fan cooling system.
 Low Torque performances working beyond the nominal speed

Standard: Not designed to work beyond the nominal speed: very limited constant power work.

Vector: Wide constant power working area. Very useful in winding applications
 Poor acceleration response: Problems in dynamic applications

Standard: High rotor inertia values. Very poor dynamic performances.

Vector: Very good dynamic performances thanks to the optimisation of the rotor design ( Ø/length ratio)
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TYPICAL PROBLEMS USING STANDARD MOTORS FOR INVERTER DUTY
 High maintenance costs: Limited expected life time

Standard: Fast degradation of winding and isolating materials due the high frequency voltage transitions.

Vector: Long life time thanks to the reinforced materials and vacuum impregnation.
 Additional motor modifying costs

Standard: Require additional motor manipulation: not prepared to fit a feedback device for close loop operation
(encoders, resolvers...), neither active fan cooling system for low speed operation.

Vector: Integrated active fan cooling system. Prepared to fit any feedback device.
 Higher Current consumption and inverter size

Standard: It’s not possible to match the motor and application speed performances. There’s only two available
winding codes: Start and delta connection.

Vector: Each motor can be manufactured with an specific winding code in order to exactly adjust de motor
current consumption to the inverter current limits.
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PRICE: STANDARD MOTOR VS VECTOR MOTOR
 Although the vector motors are more expensive than standard asynchronous motors, this
price increment is widely compensated by their technical advantages.
 In order to perform a right economical comparison between this two motor types, it will be
necessary to take into account the total cost of each COMPLETE solution:

Additional modifying costs: Feedback and active fan installation.

Motor oversizing: Due the poor performances of the standard motors working with inverter duty.

Repair costs: Material degradation due to inverter duty work.

Inverter price: Vector motors can improve the inverter sizing through the right choice of the winding code
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SECTORS & APPLICATIONS
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CONCLUSIONS
 Standard asynchronous motors are suitable for fixed speed applications and mains supply,
vector motors are suitable for inverter duty and variable speed applications.
 Main advantages of asynchronous vector motors:








No warming problems with low speed operation.
Wide constant power working range.
High dynamic response: low inertia.
High overload capacity.
Longer expected life time: repair & maintenance cost savings.
No need of motor modifications: Integrated encoder and active fan.
Reduction of inverter size: customised windings
Dimension savings: high power density
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