馬雲龍 just passed away. It is sad to hear the news. However, we are all getting old. Inevitably our professors will all fade away eventually. It was about the time of 1961 that we took his course "Electric Machinery" in NTU. I never really did well in this class for some reason. Perhaps I hated the details of intricate winding method related to the designs of motors & generators. I think this course should come with a lab work to get us familiar with the actual hardware. I think hand on experience in this course is important. We had some outdated machines operated by a technician who looked like a 退伍軍人 with a poker face & we got to see the machine only once a year. It was really a joke. I had seen many types of motors in that four years of NTU life, but never really took them apart except the one in the old electric phonograph at home. That was a little motor with black metal housing. I was particularly fascinated to see the speed control mechanism. Get back to our class, it was the assignment problems at the end of each chapter that really gave me headaches. The problems usually were quite hard & required extensive use of slide rules. I still remember the endless weekend spending time on tinkering those problems. I usually worked with 蔡宗元 as he lived nearby (長安東路 & 吉林路) at that time. However, sometime we just couldn't figure out the way to solve the problems. Here was the final backup, wait for Apo finishing his assignment & got some inside track information from him.
As far as I can remember, professor Ma got above average quality in teaching with some interest in his students. I rated him (teaching quality) above 凌霄, 江德曜, 許振發, 楊進順 & 白光弘. I once walked with him along 新生南路 & found that he was actually pretty easy to talk to & would listen to my concern & opinion. Like old soldiers, eventually our professors will all fade away & the best way to memorize professor Ma perhaps is to talk about motor & generator, his main subjects in teaching. Electric Machine is generally considered a branch of EE, Power. But Power actually consists of generation, transmission, distribution & control. Some of us switched the field & ventured into non-EE disciplines. I think very few of us actually work in the field of Power later in our career. With the coming of digital technology & semiconductor applications, the opportunities were wide open to most of us in the decade of 1970. I happened to have the opportunity to work on motors, especially step motors, dc motors & ac synchronous motors in the printers. It sounds ancient now to talk about daisy wheel printer. But between 1973 & 1987, daisy wheel printers were widely used. It actually replaced IBM's Selectric Typewriters (IST) & the famous Teletype work station at that time. Teletype was an electronic controlled communication terminal & IST were the workhorse in corporate offices. I used IST to type my Ph.D dissertation with several metal balls (font). The problems of Teletype & IST are that they got too many mechanical movable parts. Teletype has more that 600 movable parts & IST more than 300. The new Daisy Wheel Printer (DWP) got only about 10 movable parts. That is the total difference, reliability matters. What are those movable parts? Alas, they are motors: carriage, print wheel, paper feed & ribbon advance etc. These motors work hard to the moment that requires a final step of the printing: Hammer. Hammer actually is a solenoid relay. From the paper, it seems quite complicate to make a simple printing. In fact, it is hard to figure out how Teletype with so many movable parts can accomplish the task in a reasonable time. Fortunately, when I worked on DWP, I had microprocessors at my command. We found a way to convert those intricate sequence of movements to some sequential instructions, ie computer software program. After debug & check out the logic, we put the software instructions onto memory of a microprocessor. We call it firmware instead of software as we can't change the instructions after burning them onto the chip. I remember we used two Intel 8041 chips, one controls carriage & paper feed motors & the other one controls print wheel & ribbon motors. Carriage & print wheel motors are DC motors with close loop servo. Paper feed & ribbon are step motors with open loop control. Nowadays two types of printers rule the market: Ink Jet Printer (JP) & Laser Printer (LP). Why? It is the print font. Only matrix type printers can handle the font effectively. JP & LP are matrix type, construct font electronically & print it with matrix dots. It should also be mentioned that the similar motors are used widely in the disk drives to position the read/write head.
Let's get back to our main subject, motors & generators. There are three major types of electric machines: DC, AC Synchronous & AC Induction. The step motors & VRM (Variable Reluctance Machine) are similar to AC motor with no winding in the rotor (rotor is a permanent magnet). Interestingly, transformer & motor are very close in concept. If the secondary winding is cut out from the transformer (mount in the air gap) with terminals shorted, it becomes a rotor of an induction motor. The energy transfer is from the primary winding to the motor instead of going to some device like bulb. The main difference is the energy transfer to mechanical energy instead of heat & light. From the historical view point, we always think of Michael Faraday & Joseph Henry when it comes to motor & generator for their work on the interaction of electricity & magnetism. Farad (capacitance) & Henry (inductance) are the units in honor of them. With the passing of 馬雲龍, We thank him for teaching us the engineering aspect of electric machinery & enhancing us the understanding behind the physical theory.
