The qualities aspired to obtain a good permanent magnet is/are
Its both high residual flux as well as coercivity is desired for a good permanent magnet.
The type of field winding required in PMMDC is
There is no field winding used in PMMDC to create the flux.
PMMDC are smaller in size due to
There is no field winding used in PMMDC to create the flux. So it is lighter.
PMMDC offers ______ characteristics.
As the field remains constant due to the constant field, it has shunt characteristic.
Select the possible dc magnetization characteristics of permanent magnetic materials.
The magnetic field has a positive value when the magnetic field intensity, H has negative value due to coercivity property. We use second quadrant of hysteresis loop.
Mark the speed torque characteristic of the PMDC.
It is linear in nature and also analogous to shunt machine.
PMDC had no ________ excited machine.
It has no electrical excitation.
How to manage run-away issue for dc shunt motor in industry?
A PMDC motor can be used to replace the dc shunt motor in industries as they have quite identical characteristics.
A PMMDC motor has as armature resistance of 4.2 ohms. When 6 V supply is applied to motor it runs at 1215 rpm drawing 14.5 mA on no-load. The rotational losses is
Rotational losses = E*Ia = 5.939* 14.5/1000 = 86.1 mW.
PMMDC can only be armature controlled.
Due to absence of the field winding there is no option of field control.