Electricity: motive power systems – Braking – Automatic and/or with time-delay means
Patent
1986-03-31
1987-06-16
Shoop, Jr., William M.
Electricity: motive power systems
Braking
Automatic and/or with time-delay means
318629, 318599, 318345R, 363 41, 363124, G05B 1128, H02J 102
Patent
active
046738517
ABSTRACT:
A pulse width modulated DC motor operating system is disclosed which reduces the communication back to the power supply of transient spikes caused by the switching characteristics of the freewheeling diode. The switched current path comprises, in series, a DC power supply, a low pass filter including charge storage means, a DC motor armature, a FET and a resistor. A freewheeling diode is connected across the motor armature. PWM signal generating apparatus switches the FET to control average motor armature current. A capacitor is connected across the FET and diode with minimal lead length to reduce stray inductance. The capacitor is effective to communicate voltage shifts across the resistor with FET switching to the cathode of the diode and thus serve as a source of supplemental current flow through the diode during diode switching partially in preference to the charge storage means of the low pass filter, whereby the diode switching voltage spikes communicated through the low pass filter to the DC power supply are reduced in amplitude and frequency and RFI is reduced. The resistor, along with another low pass filter, also provides an average motor armature current signal for current limiting apparatus and thus serves a dual function in the circuit.
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General Motors Corporation
Ip Shik Luen Paul
Shoop Jr. William M.
Sigler Robert M.
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