Electrical Machines Questions and Answers – Permanent Magnet DC (PMDC) Motors

«
»

This set of Electrical Machines Multiple Choice Questions & Answers (MCQs) focuses on “Permanent Magnet DC (PMDC) Motors”.

1. The qualities aspired to obtain a good permanent magnet is/are ____________
a) high residual flux
b) low coercivity
c) high coercivity
d) high residual flux and high coercivity
View Answer

Answer: d
Explanation: Its both high residual flux as well as coercivity is desired for a good permanent magnet.
advertisement

2. Which type of field winding required in PMMDC?
a) series winding
b) shunt winding
c) cumulative winding
d) none of the mentioned
View Answer

Answer: d
Explanation: There is no field winding used in PMMDC to create the flux.

3. PMMDC are smaller in size due to __________
a) ansence of field winding
b) presence of smaller field winding
c) present of magnets
d) Any of the mentioned
View Answer

Answer: a
Explanation: There is no field winding used in PMMDC to create the flux. So it is lighter.
Sanfoundry Certification Contest of the Month is Live. 100+ Subjects. Participate Now!
advertisement
advertisement

4. PMMDC offers ______ characteristics.
a) shunt
b) series
c) armature
d) cumulative
View Answer

Answer: a
Explanation: As the field remains constant due to the constant field, it has shunt characteristic.

5. Select the possible dc magnetization characteristics of permanent magnetic materials.
a) DC magnetization characteristics of permanent magnetic materials - option a
b)DC magnetization characteristics of permanent magnetic materials - option b
c) DC magnetization characteristics of permanent magnetic materials - option c
d) DC magnetization characteristics of permanent magnetic materials - option d
View Answer

Answer: a
Explanation: 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.
advertisement

6. Mark the speed torque characteristic of the PMDC.
a) The speed torque characteristic of the PMDC - option a
b) The speed torque characteristic of the PMDC - option b
c) The speed torque characteristic of the PMDC - option c
d) None of the mentioned
View Answer

Answer: a
Explanation: It is linear in nature and also analogous to shunt machine.

7. PMDC had no ________ excited machine.
a) electrically
b) magnetically
c) none of the mentioned
d) least
View Answer

Answer: a
Explanation: It has no electrical excitation.
advertisement

8. How to manage run-away issue for dc shunt motor in industry?
a) By using PMDC motor
b) By using constant field motors
c) This can not be avoided
d) None of the mentioned
View Answer

Answer: a
Explanation: A PMDC motor can be used to replace the dc shunt motor in industries as they have quite identical characteristics.

9. A PMMDC motor has an 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?
a) 86.1 mW
b) 86.1 W
c) 8.6 W
d) 8.6 mW
View Answer

Answer: a
Explanation: Rotational losses = E*Ia = 5.939* 14.5/1000 = 86.1 mW.
advertisement

10. PMMDC can only be armature controlled.
a) True
b) False
View Answer

Answer: a
Explanation: Due to absence of the field winding there is no option of field control.

Sanfoundry Global Education & Learning Series – Electrical Machines.

To practice all areas of Electrical Machines, here is complete set of 1000+ Multiple Choice Questions and Answers.

advertisement
advertisement
Subscribe to our Newsletters (Subject-wise). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

Youtube | Telegram | LinkedIn | Instagram | Facebook | Twitter | Pinterest
Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

Subscribe to his free Masterclasses at Youtube & technical discussions at Telegram SanfoundryClasses.